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Because charge is conserved, it is not possible to create an antiparticle without either destroying another particle of the same charge (as is for instance the case when antiparticles are produced naturally via beta decay or the collision of cosmic rays with Earth's atmosphere), or by the simultaneous creation of both a particle and its antiparticle (pair production), which can occur in particle accelerators such as the Large Hadron Collider at CERN.
Particles and their antiparticles have equal and opposite charges, so that an uncharged particle also gives rise to an uncharged antiparticle. In many cases, the antiparticle and the particle coincide: pairs of photons, Z0 bosons, mesons, and hypothetical gravitons and some hypothetical WIMPs all self-annihilate. However, electrically neutral particles need not be identical to their antiparticles: for example, the neutron and antineutron are distinct.
History
Experiment
In 1932, soon after the prediction of positrons by Paul Dirac, Carl D. Anderson found that cosmic-ray collisions produced these particles in a cloud chamber – a particle detector in which moving electrons (or positrons) leave behind trails as they move through the gas. The electric charge-to-mass ratio of a particle can be measured by observing the radius of curling of its cloud-chamber track in a magnetic field. Positrons, because of the direction that their paths curled, were at first mistaken for electrons travelling in the opposite direction. Positron paths in a cloud-chamber trace the same helical path as an electron but rotate in the opposite direction with respect to the magnetic field direction due to their having the same magnitude of charge-to-mass ratio but with opposite charge and, therefore, opposite signed charge-to-mass ratios.
The antiproton and antineutron were found by Emilio Segrè and Owen Chamberlain in 1955 at the University of California, Berkeley. Since then, the antiparticles of many other subatomic particles have been created in particle accelerator experiments. In recent years, complete atoms of antimatter have been assembled out of antiprotons and positrons, collected in electromagnetic traps.
Dirac hole theory | Antiparticle | Wikipedia | 464 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
Solutions of the Dirac equation contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many negative energy states available. To prevent this unphysical situation from happening, Dirac proposed that a "sea" of negative-energy electrons fills the universe, already occupying all of the lower-energy states so that, due to the Pauli exclusion principle, no other electron could fall into them. Sometimes, however, one of these negative-energy particles could be lifted out of this Dirac sea to become a positive-energy particle. But, when lifted out, it would leave behind a hole in the sea that would act exactly like a positive-energy electron with a reversed charge. These holes were interpreted as "negative-energy electrons" by Paul Dirac and mistakenly identified with protons in his 1930 paper A Theory of Electrons and Protons However, these "negative-energy electrons" turned out to be positrons, and not protons.
This picture implied an infinite negative charge for the universea problem of which Dirac was aware. Dirac tried to argue that we would perceive this as the normal state of zero charge. Another difficulty was the difference in masses of the electron and the proton. Dirac tried to argue that this was due to the electromagnetic interactions with the sea, until Hermann Weyl proved that hole theory was completely symmetric between negative and positive charges. Dirac also predicted a reaction + → + , where an electron and a proton annihilate to give two photons. Robert Oppenheimer and Igor Tamm, however, proved that this would cause ordinary matter to disappear too fast. A year later, in 1931, Dirac modified his theory and postulated the positron, a new particle of the same mass as the electron. The discovery of this particle the next year removed the last two objections to his theory.
Within Dirac's theory, the problem of infinite charge of the universe remains. Some bosons also have antiparticles, but since bosons do not obey the Pauli exclusion principle (only fermions do), hole theory does not work for them. A unified interpretation of antiparticles is now available in quantum field theory, which solves both these problems by describing antimatter as negative energy states of the same underlying matter field, i.e. particles moving backwards in time.
Elementary antiparticles | Antiparticle | Wikipedia | 509 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
Composite antiparticles
Particle–antiparticle annihilation
If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles. Reactions such as + → (the two-photon annihilation of an electron-positron pair) are an example. The single-photon annihilation of an electron-positron pair, + → , cannot occur in free space because it is impossible to conserve energy and momentum together in this process. However, in the Coulomb field of a nucleus the translational invariance is broken and single-photon annihilation may occur. The reverse reaction (in free space, without an atomic nucleus) is also impossible for this reason. In quantum field theory, this process is allowed only as an intermediate quantum state for times short enough that the violation of energy conservation can be accommodated by the uncertainty principle. This opens the way for virtual pair production or annihilation in which a one particle quantum state may fluctuate into a two particle state and back. These processes are important in the vacuum state and renormalization of a quantum field theory. It also opens the way for neutral particle mixing through processes such as the one pictured here, which is a complicated example of mass renormalization.
Properties
Quantum states of a particle and an antiparticle are interchanged by the combined application of charge conjugation , parity and time reversal .
and are linear, unitary operators, is antilinear and antiunitary,
.
If denotes the quantum state of a particle with momentum and spin whose component in the z-direction is , then one has
where denotes the charge conjugate state, that is, the antiparticle. In particular a massive particle and its antiparticle transform under the same irreducible representation of the Poincaré group which means the antiparticle has the same mass and the same spin.
If , and
can be defined separately on the particles and antiparticles, then
where the proportionality sign indicates that there might be a phase on the right hand side.
As anticommutes with the charges, , particle and antiparticle have opposite electric charges q and -q.
Quantum field theory
This section draws upon the ideas, language and notation of canonical quantization of a quantum field theory.
One may try to quantize an electron field without mixing the annihilation and creation operators by writing | Antiparticle | Wikipedia | 503 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
where we use the symbol k to denote the quantum numbers p and σ of the previous section and the sign of the energy, E(k), and ak denotes the corresponding annihilation operators. Of course, since we are dealing with fermions, we have to have the operators satisfy canonical anti-commutation relations. However, if one now writes down the Hamiltonian
then one sees immediately that the expectation value of H need not be positive. This is because E(k) can have any sign whatsoever, and the combination of creation and annihilation operators has expectation value 1 or 0.
So one has to introduce the charge conjugate antiparticle field, with its own creation and annihilation operators satisfying the relations
where k has the same p, and opposite σ and sign of the energy. Then one can rewrite the field in the form
where the first sum is over positive energy states and the second over those of negative energy. The energy becomes
where E0 is an infinite negative constant. The vacuum state is defined as the state with no particle or antiparticle, i.e., and . Then the energy of the vacuum is exactly E0. Since all energies are measured relative to the vacuum, H is positive definite. Analysis of the properties of ak and bk shows that one is the annihilation operator for particles and the other for antiparticles. This is the case of a fermion.
This approach is due to Vladimir Fock, Wendell Furry and Robert Oppenheimer. If one quantizes a real scalar field, then one finds that there is only one kind of annihilation operator; therefore, real scalar fields describe neutral bosons. Since complex scalar fields admit two different kinds of annihilation operators, which are related by conjugation, such fields describe charged bosons.
Feynman–Stückelberg interpretation | Antiparticle | Wikipedia | 386 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
By considering the propagation of the negative energy modes of the electron field backward in time, Ernst Stückelberg reached a pictorial understanding of the fact that the particle and antiparticle have equal mass m and spin J but opposite charges q. This allowed him to rewrite perturbation theory precisely in the form of diagrams. Richard Feynman later gave an independent systematic derivation of these diagrams from a particle formalism, and they are now called Feynman diagrams. Each line of a diagram represents a particle propagating either backward or forward in time. In Feynman diagrams, anti-particles are shown traveling backwards in time relative to normal matter, and vice versa. This technique is the most widespread method of computing amplitudes in quantum field theory today.
Since this picture was first developed by Stückelberg, and acquired its modern form in Feynman's work, it is called the Feynman–Stückelberg interpretation of antiparticles to honor both scientists. | Antiparticle | Wikipedia | 199 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
In mathematics, the associative property is a property of some binary operations that means that rearranging the parentheses in an expression will not change the result. In propositional logic, associativity is a valid rule of replacement for expressions in logical proofs.
Within an expression containing two or more occurrences in a row of the same associative operator, the order in which the operations are performed does not matter as long as the sequence of the operands is not changed. That is (after rewriting the expression with parentheses and in infix notation if necessary), rearranging the parentheses in such an expression will not change its value. Consider the following equations:
Even though the parentheses were rearranged on each line, the values of the expressions were not altered. Since this holds true when performing addition and multiplication on any real numbers, it can be said that "addition and multiplication of real numbers are associative operations".
Associativity is not the same as commutativity, which addresses whether the order of two operands affects the result. For example, the order does not matter in the multiplication of real numbers, that is, , so we say that the multiplication of real numbers is a commutative operation. However, operations such as function composition and matrix multiplication are associative, but not (generally) commutative.
Associative operations are abundant in mathematics; in fact, many algebraic structures (such as semigroups and categories) explicitly require their binary operations to be associative.
However, many important and interesting operations are non-associative; some examples include subtraction, exponentiation, and the vector cross product. In contrast to the theoretical properties of real numbers, the addition of floating point numbers in computer science is not associative, and the choice of how to associate an expression can have a significant effect on rounding error.
Definition
Formally, a binary operation on a set is called associative if it satisfies the associative law:
, for all in .
Here, ∗ is used to replace the symbol of the operation, which may be any symbol, and even the absence of symbol (juxtaposition) as for multiplication.
, for all in .
The associative law can also be expressed in functional notation thus:
Generalized associative law | Associative property | Wikipedia | 489 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
If a binary operation is associative, repeated application of the operation produces the same result regardless of how valid pairs of parentheses are inserted in the expression. This is called the generalized associative law.
The number of possible bracketings is just the Catalan number,
, for n operations on n+1 values. For instance, a product of 3 operations on 4 elements may be written (ignoring permutations of the arguments), in possible ways:
If the product operation is associative, the generalized associative law says that all these expressions will yield the same result. So unless the expression with omitted parentheses already has a different meaning (see below), the parentheses can be considered unnecessary and "the" product can be written unambiguously as
As the number of elements increases, the number of possible ways to insert parentheses grows quickly, but they remain unnecessary for disambiguation.
An example where this does not work is the logical biconditional . It is associative; thus, is equivalent to , but most commonly means , which is not equivalent.
Examples
Some examples of associative operations include the following.
Propositional logic
Rule of replacement
In standard truth-functional propositional logic, association, or associativity are two valid rules of replacement. The rules allow one to move parentheses in logical expressions in logical proofs. The rules (using logical connectives notation) are:
and
where "" is a metalogical symbol representing "can be replaced in a proof with".
Truth functional connectives
Associativity is a property of some logical connectives of truth-functional propositional logic. The following logical equivalences demonstrate that associativity is a property of particular connectives. The following (and their converses, since is commutative) are truth-functional tautologies.
Associativity of disjunction
Associativity of conjunction
Associativity of equivalence
Joint denial is an example of a truth functional connective that is not associative.
Non-associative operation
A binary operation on a set S that does not satisfy the associative law is called non-associative. Symbolically,
For such an operation the order of evaluation does matter. For example:
Subtraction
Division
Exponentiation
Vector cross product
Also although addition is associative for finite sums, it is not associative inside infinite sums (series). For example,
whereas | Associative property | Wikipedia | 511 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Some non-associative operations are fundamental in mathematics. They appear often as the multiplication in structures called non-associative algebras, which have also an addition and a scalar multiplication. Examples are the octonions and Lie algebras. In Lie algebras, the multiplication satisfies Jacobi identity instead of the associative law; this allows abstracting the algebraic nature of infinitesimal transformations.
Other examples are quasigroup, quasifield, non-associative ring, and commutative non-associative magmas.
Nonassociativity of floating point calculation
In mathematics, addition and multiplication of real numbers are associative. By contrast, in computer science, addition and multiplication of floating point numbers are not associative, as different rounding errors may be introduced when dissimilar-sized values are joined in a different order.
To illustrate this, consider a floating point representation with a 4-bit significand:
Even though most computers compute with 24 or 53 bits of significand, this is still an important source of rounding error, and approaches such as the Kahan summation algorithm are ways to minimise the errors. It can be especially problematic in parallel computing.
Notation for non-associative operations
In general, parentheses must be used to indicate the order of evaluation if a non-associative operation appears more than once in an expression (unless the notation specifies the order in another way, like ). However, mathematicians agree on a particular order of evaluation for several common non-associative operations. This is simply a notational convention to avoid parentheses.
A left-associative operation is a non-associative operation that is conventionally evaluated from left to right, i.e.,
while a right-associative operation is conventionally evaluated from right to left:
Both left-associative and right-associative operations occur. Left-associative operations include the following:
Subtraction and division of real numbers
Function application
This notation can be motivated by the currying isomorphism, which enables partial application. | Associative property | Wikipedia | 445 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Right-associative operations include the following:
Exponentiation of real numbers in superscript notation
Exponentiation is commonly used with brackets or right-associatively because a repeated left-associative exponentiation operation is of little use. Repeated powers would mostly be rewritten with multiplication:
Formatted correctly, the superscript inherently behaves as a set of parentheses; e.g. in the expression the addition is performed before the exponentiation despite there being no explicit parentheses wrapped around it. Thus given an expression such as , the full exponent of the base is evaluated first. However, in some contexts, especially in handwriting, the difference between , and can be hard to see. In such a case, right-associativity is usually implied.
Function definition
Using right-associative notation for these operations can be motivated by the Curry–Howard correspondence and by the currying isomorphism.
Non-associative operations for which no conventional evaluation order is defined include the following.
Exponentiation of real numbers in infix notation
Knuth's up-arrow operators
Taking the cross product of three vectors
Taking the pairwise average of real numbers
Taking the relative complement of sets
.(Compare material nonimplication in logic.)
History
William Rowan Hamilton seems to have coined the term "associative property" around 1844, a time when he was contemplating the non-associative algebra of the octonions he had learned about from John T. Graves. | Associative property | Wikipedia | 310 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Apatosaurus (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Apatosaurus lived about 152 to 151 million years ago (mya), during the late Kimmeridgian to early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus had an average length of , and an average mass of . A few specimens indicate a maximum length of 11–30% greater than average and a mass of approximately .
The cervical vertebrae of Apatosaurus are less elongated and more heavily constructed than those of Diplodocus, a diplodocid like Apatosaurus, and the bones of the leg are much stockier despite being longer, implying that Apatosaurus was a more robust animal. The tail was held above the ground during normal locomotion. Apatosaurus had a single claw on each forelimb and three on each hindlimb. The Apatosaurus skull, long thought to be similar to Camarasaurus, is much more similar to that of Diplodocus. Apatosaurus was a generalized browser that likely held its head elevated. To lighten its vertebrae, Apatosaurus had air sacs that made the bones internally full of holes. Like that of other diplodocids, its tail may have been used as a whip to create loud noises, or, as more recently suggested, as a sensory organ.
The skull of Apatosaurus was confused with that of Camarasaurus and Brachiosaurus until 1909, when the holotype of A. louisae was found, and a complete skull just a few meters away from the front of the neck. Henry Fairfield Osborn disagreed with this association, and went on to mount a skeleton of Apatosaurus with a Camarasaurus skull cast. Apatosaurus skeletons were mounted with speculative skull casts until 1970, when McIntosh showed that more robust skulls assigned to Diplodocus were more likely from Apatosaurus. | Apatosaurus | Wikipedia | 477 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus is a genus in the family Diplodocidae. It is one of the more basal genera, with only Amphicoelias and possibly a new, unnamed genus more primitive. Although the subfamily Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 study. Only Brontosaurus is also in the subfamily, with the other genera being considered synonyms or reclassified as diplodocines. Brontosaurus has long been considered a junior synonym of Apatosaurus; its type species was reclassified as A.excelsus in 1903. A 2015 study concluded that Brontosaurus is a valid genus of sauropod distinct from Apatosaurus, but not all paleontologists agree with this division. As it existed in North America during the late Jurassic, Apatosaurus would have lived alongside dinosaurs such as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus.
Description
Apatosaurus was a large, long-necked, quadrupedal animal with a long, whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. Most size estimates are based on specimen CM3018, the type specimen of A.louisae, reaching in length and in body mass. A 2015 study that estimated the mass of volumetric models of Dreadnoughtus, Apatosaurus, and Giraffatitan estimates CM3018 at , similar in mass to Dreadnoughtus. Some specimens of A.ajax (such as OMNH1670) represent individuals 1130% longer, suggesting masses twice that of CM3018 or , potentially rivaling the largest titanosaurs. However, the upper size estimate of OMNH1670 is likely an exaggeration, with the size estimates revised in 2020 at in length and in body mass based on volumetric analysis. | Apatosaurus | Wikipedia | 382 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The skull is small in relation to the size of the animal. The jaws are lined with spatulate (chisel-like) teeth suited to an herbivorous diet. The snout of Apatosaurus and similar diplodocoids is squared, with only Nigersaurus having a squarer skull. The braincase of Apatosaurus is well preserved in specimen BYU17096, which also preserved much of the skeleton. A phylogenetic analysis found that the braincase had a morphology similar to those of other diplodocoids. Some skulls of Apatosaurus have been found still in articulation with their teeth. Those teeth that have the enamel surface exposed do not show any scratches on the surface; instead, they display a sugary texture and little wear. | Apatosaurus | Wikipedia | 156 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Like those of other sauropods, the neck vertebrae are deeply bifurcated; they carried neural spines with a large trough in the middle, resulting in a wide, deep neck. The vertebral formula for the holotype of A.louisae is 15cervicals, 10dorsals, 5sacrals, and 82caudals. The caudal vertebra number may vary, even within species. The cervical vertebrae of Apatosaurus and Brontosaurus are stouter and more robust than those of other diplodocids and were found to be most similar to Camarasaurus by Charles Whitney Gilmore. In addition, they support cervical ribs that extend farther towards the ground than in diplodocines, and have vertebrae and ribs that are narrower towards the top of the neck, making the neck nearly triangular in cross-section. In Apatosaurus louisae, the atlas-axis complex of the first cervicals is nearly fused. The dorsal ribs are not fused or tightly attached to their vertebrae and are instead loosely articulated. Apatosaurus has ten dorsal ribs on either side of the body. The large neck was filled with an extensive system of weight-saving air sacs. Apatosaurus, like its close relative Supersaurus, has tall neural spines, which make up more than half the height of the individual bones of its vertebrae. The shape of the tail is unusual for a diplodocid; it is comparatively slender because of the rapidly decreasing height of the vertebral spines with increasing distance from the hips. Apatosaurus also had very long ribs compared to most other diplodocids, giving it an unusually deep chest. As in other diplodocids, the tail transformed into a whip-like structure towards the end. | Apatosaurus | Wikipedia | 366 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The limb bones are also very robust. Within Apatosaurinae, the scapula of Apatosaurus louisae is intermediate in morphology between those of A.ajax and Brontosaurus excelsus. The arm bones are stout, so the humerus of Apatosaurus resembles that of Camarasaurus, as well as Brontosaurus. However, the humeri of Brontosaurus and A.ajax are more similar to each other than they are to A.louisae. In 1936, Charles Gilmore noted that previous reconstructions of Apatosaurus forelimbs erroneously proposed that the radius and ulna could cross; in life they would have remained parallel. Apatosaurus had a single large claw on each forelimb, a feature shared by all sauropods more derived than Shunosaurus. The first three toes had claws on each hindlimb. The phalangeal formula is 2-1-1-1-1, meaning the innermost finger (phalanx) on the forelimb has two bones and the next has one. The single manual claw bone (ungual) is slightly curved and squarely truncated on the anterior end. The pelvic girdle includes the robust ilia, and the fused (co-ossified) pubes and ischia. The femora of Apatosaurus are very stout and represent some of the most robust femora of any member of Sauropoda. The tibia and fibula bones are different from the slender bones of Diplodocus but are nearly indistinguishable from those of Camarasaurus. The fibula is longer and slenderer than the tibia. The foot of Apatosaurus has three claws on the innermost digits; the digit formula is 3-4-5-3-2. The first metatarsal is the stoutest, a feature shared among diplodocids.
Discovery and species
Initial discovery | Apatosaurus | Wikipedia | 396 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The first Apatosaurus fossils were discovered by Arthur Lakes, a local miner, and his friend Henry C. Beckwith in the spring of 1877 in Morrison, a town in the eastern foothills of the Rocky Mountains in Jefferson County, Colorado. Arthur Lakes wrote to Othniel Charles Marsh, Professor of Paleontology at Yale University, and Edward Drinker Cope, a paleontologist based in Philadelphia, about the discovery until eventually collecting several fossils and sending them to both paleontologists. Marsh named Atlantosaurus montanus based on some of the fossils sent and hired Lakes to collect the rest of the material at Morrison and send it to Yale, while Cope attempted to hire Lakes as well but was rejected. One of the best specimens collected by Lakes in 1877 was a well preserved partial postcranial skeleton, including many vertebrae, and a partial braincase (YPM VP 1860), which was sent to Marsh and named Apatosaurus ajax in November 1877. The composite term Apatosaurus comes from the Greek words ()/ () meaning "deception"/"deceptive", and () meaning "lizard"; thus, "deceptive lizard". Marsh gave it this name based on the chevron bones, which are dissimilar to those of other dinosaurs; instead, the chevron bones of Apatosaurus showed similarities with those of mosasaurs, most likely that of the representative species Mosasaurus. By the end of excavations at Lakes' quarry in Morrison, several partial specimens of Apatosaurus had been collected, but only the type specimen of A. ajax can be confidently referred to the species. | Apatosaurus | Wikipedia | 331 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
During excavation and transportation, the bones of the holotype skeleton were mixed with those of another Apatosaurine individual originally described as Atlantosaurus immanis; as a consequence, some elements cannot be ascribed to either specimen with confidence. Marsh distinguished the new genus Apatosaurus from Atlantosaurus on the basis of the number of sacral vertebrae, with Apatosaurus possessing three and Atlantosaurus four. Recent research shows that traits usually used to distinguish taxa at this time were actually widespread across several taxa, causing many of the taxa named to be invalid, like Atlantosaurus. Two years later, Marsh announced the discovery of a larger and more complete specimen (YPM VP 1980) from Como Bluff, Wyoming, he gave this specimen the name Brontosaurus excelsus. Also at Como Bluff, the Hubbell brothers working for Edward Drinker Cope collected a tibia, fibula, scapula, and several caudal vertebrae along with other fragments belonging to Apatosaurus in 1877–78 at Cope's Quarry 5 at the site. Later in 1884, Othniel Marsh named Diplodocus lacustris based on a chimeric partial dentary, snout, and several teeth collected by Lakes in 1877 at Morrison. In 2013, it was suggested that the dentary of D. lacustris and its teeth were actually from Apatosaurus ajax based on its proximity to the type braincase of A. ajax. All specimens currently considered Apatosaurus were from the Morrison Formation, the location of the excavations of Marsh and Cope. | Apatosaurus | Wikipedia | 319 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Second Dinosaur Rush and skull issue
After the end of the Bone Wars, many major institutions in the eastern United States were inspired by the depictions and finds by Marsh and Cope to assemble their own dinosaur fossil collections. The competition to mount the first sauropod skeleton specifically was the most intense, with the American Museum of Natural History, Carnegie Museum of Natural History, and Field Museum of Natural History all sending expeditions to the west to find the most complete sauropod specimen, bring it back to the home institution, and mount it in their fossil halls. The American Museum of Natural History was the first to launch an expedition, finding a well preserved skeleton (AMNH 460), which is occasionally assigned to Apatosaurus, is considered nearly complete; only the head, feet, and sections of the tail are missing, and it was the first sauropod skeleton mounted. The specimen was found north of Medicine Bow, Wyoming, in 1898 by Walter Granger, and took the entire summer to extract. To complete the mount, sauropod feet that were discovered at the same quarry and a tail fashioned to appear as Marsh believed it shouldbut which had too few vertebraewere added. In addition, a sculpted model of what the museum thought the skull of this massive creature might look like was made. This was not a delicate skull like that of Diplodocuswhich was later found to be more accuratebut was based on "the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries". These skulls were likely those of Camarasaurus, the only other sauropod for which good skull material was known at the time. The mount construction was overseen by Adam Hermann, who failed to find Apatosaurus skulls. Hermann was forced to sculpt a stand-in skull by hand. Osborn said in a publication that the skull was "largely conjectural and based on that of Morosaurus" (now Camarasaurus). | Apatosaurus | Wikipedia | 399 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1903, Elmer Riggs published a study that described a well-preserved skeleton of a diplodocid from the Grand River Valley near Fruita, Colorado, Field Museum of Natural History specimen P25112. Riggs thought that the deposits were similar in age to those of the Como Bluff in Wyoming from which Marsh had described Brontosaurus. Most of the skeleton was found, and after comparison with both Brontosaurus and Apatosaurus ajax, Riggs realized that the holotype of A.ajax was immature, and thus the features distinguishing the genera were not valid. Since Apatosaurus was the earlier name, Brontosaurus should be considered a junior synonym of Apatosaurus. Because of this, Riggs recombined Brontosaurus excelsus as Apatosaurus excelsus. Based on comparisons with other species proposed to belong to Apatosaurus, Riggs also determined that the Field Columbian Museum specimen was likely most similar to A.excelsus. | Apatosaurus | Wikipedia | 198 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Despite Riggs' publication, Henry Fairfield Osborn, who was a strong opponent of Marsh and his taxa, labeled the Apatosaurus mount of the American Museum of Natural History Brontosaurus. Because of this decision the name Brontosaurus was commonly used outside of scientific literature for what Riggs considered Apatosaurus, and the museum's popularity meant that Brontosaurus became one of the best known dinosaurs, even though it was invalid throughout nearly all of the 20th and early 21st centuries.
It was not until 1909 that an Apatosaurus skull was found during the first expedition, led by Earl Douglass, to what would become known as the Carnegie Quarry at Dinosaur National Monument. The skull was found a short distance from a skeleton (specimen CM3018) identified as the new species Apatosaurus louisae, named after Louise Carnegie, wife of Andrew Carnegie, who funded field research to find complete dinosaur skeletons in the American West. The skull was designated CM11162; it was very similar to the skull of Diplodocus. Another smaller skeleton of A.louisae was found nearby CM11162 and CM3018. The skull was accepted as belonging to the Apatosaurus specimen by Douglass and Carnegie Museum director William H. Holland, although other scientistsmost notably Osbornrejected this identification. Holland defended his view in 1914 in an address to the Paleontological Society of America, yet he left the Carnegie Museum mount headless. While some thought Holland was attempting to avoid conflict with Osborn, others suspected Holland was waiting until an articulated skull and neck were found to confirm the association of the skull and skeleton. After Holland's death in 1934, museum staff placed a cast of a Camarasaurus skull on the mount.
While most other museums were using cast or sculpted Camarasaurus skulls on Apatosaurus mounts, the Yale Peabody Museum decided to sculpt a skull based on the lower jaw of a Camarasaurus, with the cranium based on Marsh's 1891 illustration of the skull. The skull also included forward-pointing nasalssomething unusual for any dinosaurand fenestrae differing from both the drawing and other skulls. | Apatosaurus | Wikipedia | 433 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
No Apatosaurus skull was mentioned in literature until the 1970s when John Stanton McIntosh and David Berman redescribed the skulls of Diplodocus and Apatosaurus. They found that though he never published his opinion, Holland was almost certainly correct, that Apatosaurus had a Diplodocus-like skull. According to them, many skulls long thought to pertain to Diplodocus might instead be those of Apatosaurus. They reassigned multiple skulls to Apatosaurus based on associated and closely associated vertebrae. Even though they supported Holland, it was noted that Apatosaurus might have possessed a Camarasaurus-like skull, based on a disarticulated Camarasaurus-like tooth found at the precise site where an Apatosaurus specimen was found years before. On October20, 1979, after the publications by McIntosh and Berman, the first true skull of Apatosaurus was mounted on a skeleton in a museum, that of the Carnegie. In 1998, it was suggested that the Felch Quarry skull that Marsh had included in his 1896 skeletal restoration instead belonged to Brachiosaurus. This was supported in 2020 with a redescription of the brachiosaurid material found at the Felch Quarry.
Recent discoveries and reassessment
In 2011, the first specimen of Apatosaurus where a skull was found articulated with its cervical vertebrae was described. This specimen, CMCVP7180, was found to differ in both skull and neck features from A.louisae, but shared many features of the cervical vertebrae with A.ajax. Another well-preserved skull is Brigham Young University specimen 17096, a well-preserved skull and skeleton, with a preserved braincase. The specimen was found in Cactus Park Quarry in western Colorado. In 2013, Matthew Mossbrucker and several other authors published an abstract that described a premaxilla and maxilla from Lakes' original quarry in Morrison and referred the material to Apatosaurus ajax. | Apatosaurus | Wikipedia | 398 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Almost all modern paleontologists agreed with Riggs that the two dinosaurs should be classified together in a single genus. According to the rules of the ICZN (which governs the scientific names of animals), the name Apatosaurus, having been published first, has priority as the official name; Brontosaurus was considered a junior synonym and was therefore long discarded from formal use. Despite this, at least one paleontologistRobert T. Bakkerargued in the 1990s that A.ajax and A.excelsus were in fact sufficiently distinct for the latter to merit a separate genus. | Apatosaurus | Wikipedia | 122 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2015, Emanuel Tschopp, Octávio Mateus, and Roger Benson released a paper on diplodocoid systematics, and proposed that genera could be diagnosed by thirteen differing characters, and species separated based on six. The minimum number for generic separation was chosen based on the fact that A.ajax and A.louisae differ in twelve characters, and Diplodocus carnegiei and D.hallorum differ in eleven characters. Thus, thirteen characters were chosen to validate the separation of genera. The six differing features for specific separation were chosen by counting the number of differing features in separate specimens generally agreed to represent one species, with only one differing character in D.carnegiei and A.louisae, but five differing features in B.excelsus. Therefore, Tschopp etal. argued that Apatosaurus excelsus, originally classified as Brontosaurus excelsus, had enough morphological differences from other species of Apatosaurus that it warranted being reclassified as a separate genus again. The conclusion was based on a comparison of 477 morphological characteristics across 81 different dinosaur individuals. Among the many notable differences are the widerand presumably strongerneck of Apatosaurus species compared to B.excelsus. Other species previously assigned to Apatosaurus, such as Elosaurus parvus and Eobrontosaurus yahnahpin were also reclassified as Brontosaurus. Some features proposed to separate Brontosaurus from Apatosaurus include: posterior dorsal vertebrae with the centrum longer than wide; the scapula rear to the acromial edge and the distal blade being excavated; the acromial edge of the distal scapular blade bearing a rounded expansion; and the ratio of the proximodistal length to transverse breadth of the astragalus 0.55 or greater. Sauropod expert Michael D'Emic pointed out that the criteria chosen were to an extent arbitrary and that they would require abandoning the name Brontosaurus again if newer analyzes obtained different results. Mammal paleontologist Donald Prothero criticized the mass media reaction to this study as superficial and premature, concluding that he would keep "Brontosaurus" in quotes and not treat the name as a valid genus.
Valid species | Apatosaurus | Wikipedia | 452 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Many species of Apatosaurus have been designated from scant material. Marsh named as many species as he could, which resulted in many being based upon fragmentary and indistinguishable remains. In 2005, Paul Upchurch and colleagues published a study that analyzed the species and specimen relationships of Apatosaurus. They found that A.louisae was the most basal species, followed by FMNHP25112, and then a polytomy of A.ajax, A.parvus, and A.excelsus. Their analysis was revised and expanded with many additional diplodocid specimens in 2015, which resolved the relationships of Apatosaurus slightly differently, and also supported separating Brontosaurus from Apatosaurus. | Apatosaurus | Wikipedia | 149 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus ajax was named by Marsh in 1877 after Ajax, a hero from Greek mythology. Marsh designated the incomplete, juvenile skeleton YPM1860 as its holotype. The species is less studied than Brontosaurus and A.louisae, especially because of the incomplete nature of the holotype. In 2005, many specimens in addition to the holotype were found assignable to A.ajax, YPM1840, NSMT-PV 20375, YPM1861, and AMNH460. The specimens date from the late Kimmeridgian to the early Tithonian ages. In 2015, only the A.ajax holotype YPM1860 assigned to the species, with AMNH460 found either to be within Brontosaurus, or potentially its own taxon. However, YPM1861 and NSMT-PV 20375 only differed in a few characteristics, and cannot be distinguished specifically or generically from A.ajax. YPM1861 is the holotype of "Atlantosaurus" immanis, which means it might be a junior synonym of A.ajax.
Apatosaurus louisae was named by Holland in 1916, being first known from a partial skeleton that was found in Utah. The holotype is CM3018, with referred specimens including CM3378, CM11162, and LACM52844. The former two consist of a vertebral column; the latter two consist of a skull and a nearly complete skeleton, respectively. Apatosaurus louisae specimens all come from the late Kimmeridgian of Dinosaur National Monument. In 2015, Tschopp etal. found the type specimen of Apatosaurus laticollis to nest closely with CM3018, meaning the former is likely a junior synonym of A.louisae.
The cladogram below is the result of an analysis by Tschopp, Mateus, and Benson (2015). The authors analyzed most diplodocid type specimens separately to deduce which specimen belonged to which species and genus.
Reassigned species | Apatosaurus | Wikipedia | 434 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus grandis was named in 1877 by Marsh in the article that described A.ajax. It was briefly described, figured, and diagnosed. Marsh later mentioned it was only provisionally assigned to Apatosaurus when he reassigned it to his new genus Morosaurus in 1878. Since Morosaurus has been considered a synonym of Camarasaurus, C.grandis is the oldest-named species of the latter genus.
Apatosaurus excelsus was the original type species of Brontosaurus, first named by Marsh in 1879. Elmer Riggs reclassified Brontosaurus as a synonym of Apatosaurus in 1903, transferring the species B.excelsus to A.excelsus. In 2015, Tschopp, Mateus, and Benson argued that the species was distinct enough to be placed in its own genus, so they reclassified it back into Brontosaurus.
Apatosaurus parvus, first described from a juvenile specimen as Elosaurus in 1902 by Peterson and Gilmore, was reassigned to Apatosaurus in 1994, and then to Brontosaurus in 2015. Many other, more mature specimens were assigned to it following the 2015 study.
Apatosaurus minimus was originally described as a specimen of Brontosaurus sp. in 1904 by Osborn. In 1917, Henry Mook named it as its own species, A.minimus, for a pair of ilia and their sacrum. In 2012, Mike P. Taylor and Matt J. Wedel published a short abstract describing the material of A. minimus, finding it hard to place among either Diplodocoidea or Macronaria. While it was placed with Saltasaurus in a phylogenetic analysis, it was thought to represent instead some form with convergent features from many groups. The study of Tschopp etal. did find that a camarasaurid position for the taxon was supported, but noted that the position of the taxon was found to be highly variable and there was no clearly more likely position.
Apatosaurus alenquerensis was named in 1957 by Albert-Félix de Lapparent and Georges Zbyweski. It was based on post cranial material from Portugal. In 1990, this material was reassigned to Camarasaurus, but in 1998 it was given its own genus, Lourinhasaurus. This was further supported by the findings of Tschopp etal. in 2015, where Lourinhasaurus was found to be sister to Camarasaurus and other camarasaurids. | Apatosaurus | Wikipedia | 505 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus yahnahpin was named by James Filla and Patrick Redman in 1994. Bakker made A.yahnahpin the type species of a new genus, Eobrontosaurus in 1998, and Tschopp reclassified it as Brontosaurus yahnahpin in 2015. | Apatosaurus | Wikipedia | 63 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Classification
Apatosaurus is a member of the family Diplodocidae, a clade of gigantic sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus, Supersaurus, and Barosaurus. Apatosaurus is sometimes classified in the subfamily Apatosaurinae, which may also include Suuwassea, Supersaurus, and Brontosaurus. Othniel Charles Marsh described Apatosaurus as allied to Atlantosaurus within the now-defunct group Atlantosauridae. In 1878, Marsh raised his family to the rank of suborder, including Apatosaurus, Atlantosaurus, Morosaurus (=Camarasaurus) and Diplodocus. He classified this group within Sauropoda, a group he erected in the same study. In 1903, Elmer S. Riggs said the name Sauropoda would be a junior synonym of earlier names; he grouped Apatosaurus within Opisthocoelia. Sauropoda is still used as the group name. In 2011, John Whitlock published a study that placed Apatosaurus a more basal diplodocid, sometimes less basal than Supersaurus.
Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).
Paleobiology
It was believed throughout the 19th and early 20th centuries that sauropods like Apatosaurus were too massive to support their own weight on dry land. It was theorized that they lived partly submerged in water, perhaps in swamps. More recent findings do not support this; sauropods are now thought to have been fully terrestrial animals. A study of diplodocid snouts showed that the square snout, large proportion of pits, and fine, subparallel scratches of the teeth of Apatosaurus suggests it was a ground-height, nonselective browser. It may have eaten ferns, cycadeoids, seed ferns, horsetails, and algae. Stevens and Parish (2005) speculate that these sauropods fed from riverbanks on submerged water plants. | Apatosaurus | Wikipedia | 435 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A 2015 study of the necks of Apatosaurus and Brontosaurus found many differences between them and other diplodocids, and that these variations may have shown that the necks of Apatosaurus and Brontosaurus were used for intraspecific combat. Various uses for the single claw on the forelimb of sauropods have been proposed. One suggestion is that they were used for defense, but their shape and size make this unlikely. It was also possible they were for feeding, but the most probable use for the claw was grasping objects such as tree trunks when rearing.
Trackways of sauropods like Apatosaurus show that they may have had a range of around per day, and that they could potentially have reached a top speed of per hour. The slow locomotion of sauropods may be due to their minimal muscling, or to recoil after strides. A trackway of a juvenile has led some to believe that they were capable of bipedalism, though this is disputed.
Neck posture
Diplodocids like Apatosaurus are often portrayed with their necks held high up in the air, allowing them to browse on tall trees. Some studies state diplodocid necks were less flexible than previously believed, because the structure of the neck vertebrae would not have allowed the neck to bend far upward, and that sauropods like Apatosaurus were adapted to low browsing or ground feeding.
Other studies by Taylor find that all tetrapods appear to hold their necks at the maximum possible vertical extension when in a normal, alert posture; they argue the same would hold true for sauropods barring any unknown, unique characteristics that set the soft tissue anatomy of their necks apart from that of other animals. Apatosaurus, like Diplodocus, would have held its neck angled upward with the head pointing downward in a resting posture. Kent Stevens and Michael Parrish (1999 and 2005) state Apatosaurus had a great feeding range; its neck could bend into a U-shape laterally. The neck's range of movement would have also allowed the head to feed at the level of the feet. | Apatosaurus | Wikipedia | 439 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Matthew Cobley et al. (2013) dispute this, finding that large muscles and cartilage would have limited movement of the neck. They state the feeding ranges for sauropods like Diplodocus were smaller than previously believed, and the animals may have had to move their whole bodies around to better access areas where they could browse vegetation. As such, they might have spent more time foraging to meet their minimum energy needs. The conclusions of Cobley etal. are disputed by Taylor, who analyzed the amount and positioning of intervertebral cartilage to determine the flexibility of the neck of Apatosaurus and Diplodocus. He found that the neck of Apatosaurus was very flexible.
Physiology
Given the large body mass and long neck of sauropods like Apatosaurus, physiologists have encountered problems determining how these animals breathed. Beginning with the assumption that, like crocodilians, Apatosaurus did not have a diaphragm, the dead-space volume (the amount of unused air remaining in the mouth, trachea, and air tubes after each breath) has been estimated at for a specimen. Paladino calculates its tidal volume (the amount of air moved in or out during a single breath) at with an avian respiratory system, if mammalian, and if reptilian.
On this basis, its respiratory system would likely have been parabronchi, with multiple pulmonary air sacs as in avian lungs, and a flow-through lung. An avian respiratory system would need a lung volume of about compared with a mammalian requirement of , which would exceed the space available. The overall thoracic volume of Apatosaurus has been estimated at , allowing for a , four-chambered heart and a lung capacity. That would allow about for the necessary tissue. Evidence for the avian system in Apatosaurus and other sauropods is also present in the pneumaticity of the vertebrae. Though this plays a role in reducing the weight of the animal, Wedel (2003) states they are also likely connected to air sacs, as in birds. | Apatosaurus | Wikipedia | 435 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
James Spotila et al. (1991) concludes that the large body size of sauropods would have made them unable to maintain high metabolic rates because they would not have been able to release enough heat. They assumed sauropods had a reptilian respiratory system. Wedel says that an avian system would have allowed it to dump more heat. Some scientists state that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain. Others suggest that the near-horizontal posture of the head and neck would have eliminated the problem of supplying blood to the brain because it would not have been elevated.
James Farlow (1987) calculates that an Apatosaurus-sized dinosaur about would have possessed of fermentation contents, though he cautions that the regression equation being used is based on living mammals which are much smaller and physiologically different. Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism, Frank Paladino etal. (1997) estimate the animal would have needed to consume only about of water per day.
Growth
A 1999 microscopic study of Apatosaurus and Brontosaurus bones concluded the animals grew rapidly when young and reached near-adult sizes in about 10years. In 2008, a study on the growth rates of sauropods was published by Thomas Lehman and Holly Woodward. They said that by using growth lines and length-to-mass ratios, Apatosaurus would have grown to 25t (25 long tons; 28 short tons) in 15years, with growth peaking at in a single year. An alternative method, using limb length and body mass, found Apatosaurus grew per year, and reached its full mass before it was about 70years old. These estimates have been called unreliable because the calculation methods are not sound; old growth lines would have been obliterated by bone remodeling. One of the first identified growth factors of Apatosaurus was the number of sacral vertebrae, which increased to five by the time of the creature's maturity. This was first noted in 1903 and again in 1936. | Apatosaurus | Wikipedia | 426 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Eva Griebeler etal. (2013) examined long-bone histological data and concluded the Apatosaurus sp.SMA0014 weighed , reached sexual maturity at 21years, and died aged 28. The same growth model indicated Apatosaurus sp.BYU 601–17328 weighed , reached sexual maturity at 19years, and died aged 31.
Juveniles
Compared with most sauropods, a relatively large amount of juvenile material is known from Apatosaurus. Multiple specimens in the OMNH are from juveniles of an undetermined species of Apatosaurus; this material includes partial shoulder and pelvic girdles, some vertebrae, and limb bones. OMNH juvenile material is from at least two different age groups and based on overlapping bones likely comes from more than three individuals. The specimens exhibit features that distinguish Apatosaurus from its relatives, and thus likely belong to the genus. Juvenile sauropods tend to have proportionally shorter necks and tails, and a more pronounced forelimb-hindlimb disparity than found in adult sauropods.
Tail
An article published in 1997 reported research of the mechanics of Apatosaurus tails by Nathan Myhrvold and paleontologist Philip J. Currie. Myhrvold carried out a computer simulation of the tail, which in diplodocids like Apatosaurus was a very long, tapering structure resembling a bullwhip. This computer modeling suggested diplodocids were capable of producing a whiplike cracking sound of over 200 decibels, comparable to the volume of a cannon being fired. | Apatosaurus | Wikipedia | 345 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A pathology has been identified on the tail of Apatosaurus, caused by a growth defect. Two caudal vertebrae are seamlessly fused along the entire articulating surface of the bone, including the arches of the neural spines. This defect might have been caused by the lack or inhibition of the substance that forms intervertebral disks or joints. It has been proposed that the whips could have been used in combat and defense, but the tails of diplodocids were quite light and narrow compared to Shunosaurus and mamenchisaurids, and thus to injure another animal with the tail would severely injure the tail itself. More recently, Baron (2020) considers the use of the tail as a bullwhip unlikely because of the potentially catastrophic muscle and skeletal damage such speeds could cause on the large and heavy tail. Instead, he proposes that the tails might have been used as a tactile organ to keep in touch with the individuals behind and on the sides in a group while migrating, which could have augmented cohesion and allowed communication among individuals while limiting more energetically demanding activities like stopping to search for dispersed individuals, turning to visually check on individuals behind, or communicating vocally.
Paleoecology
The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, dates from between 156.3mya at its base, and 146.8mya at the top, placing it in the late Oxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period. This formation is interpreted as originating in a locally semiarid environment with distinct wet and dry seasons. The Morrison Basin, where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan; it was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins were carried by streams and rivers and deposited in swampy lowlands, lakes, river channels, and floodplains. This formation is similar in age to the Lourinhã Formation in Portugal and the Tendaguru Formation in Tanzania. | Apatosaurus | Wikipedia | 434 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus was the second most common sauropod in the Morrison Formation ecosystem, after Camarasaurus. Apatosaurus may have been more solitary than other Morrison Formation dinosaurs. Fossils of the genus have only been found in the upper levels of the formation. Those of Apatosaurus ajax are known exclusively from the upper Brushy Basin Member, about 152–151 mya. A.louisae fossils are rare, known only from one site in the upper Brushy Basin Member; they date to the late Kimmeridgian stage, about 151mya. Additional Apatosaurus remains are known from similarly aged or slightly younger rocks, but they have not been identified as any particular species, and thus may instead belong to Brontosaurus. | Apatosaurus | Wikipedia | 150 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Morrison Formation records a time when the local environment was dominated by gigantic sauropod dinosaurs. Dinosaurs known from the Morrison Formation include the theropods Allosaurus, Ceratosaurus, Ornitholestes, and Torvosaurus; the sauropods Brontosaurus, Brachiosaurus, Camarasaurus, and Diplodocus; and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Apatosaurus is commonly found at the same sites as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus. Allosaurus accounted for 70–75% of theropod specimens and was at the top trophic level of the Morrison food web. Many of the dinosaurs of the Morrison Formation are of the same genera as those seen in Portuguese rocks of the Lourinhã Formationmainly Allosaurus, Ceratosaurus, and Torvosaurusor have a close counterpartBrachiosaurus and Lusotitan, Camptosaurus and Draconyx, and Apatosaurus and Dinheirosaurus. Other vertebrates that are known to have shared this paleo-environment include ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, and several species of pterosaur. Shells of bivalves and aquatic snails are also common. The flora of the period has been evidenced in fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns with fern understory (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum. | Apatosaurus | Wikipedia | 364 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus () is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period (Kimmeridgian to late Tithonian ages). The name "Allosaurus" means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae. It is derived from the Greek words () ("different", "strange", or "other") and () ("lizard" or "reptile"). The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. The genus has a very complicated taxonomy and includes at least three valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from the Alcobaça Formation and Lourinhã Formation in Portugal with teeth known from Germany. It was known for over half of the 20th century as Antrodemus, but a study of the abundant remains from the Cleveland-Lloyd Dinosaur Quarry returned the name "Allosaurus" to prominence. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Allosaurus was a large bipedal predator for its time. Its skull was light, robust, and equipped with dozens of sharp, serrated teeth. It averaged in length for A. fragilis, with the largest specimens estimated as being long. Relative to the large and powerful legs, its three-fingered hands were small and the body was balanced by a long, muscular tail. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur. As the most abundant large predator of the Morrison Formation, Allosaurus was at the top of the food chain and probably preyed on contemporaneous large herbivorous dinosaurs, with the possibility of hunting other predators. Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior and hunting in packs, while others believe individuals may have been aggressive toward each other and that congregations of this genus are the result of lone individuals feeding on the same carcasses.
Discovery and history
Early discoveries and research | Allosaurus | Wikipedia | 491 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century. The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869. It came from Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. The locals had identified such bones as "petrified horse hoofs". Hayden sent his specimen to Joseph Leidy, who identified it as half of a tail vertebra and tentatively assigned it to the European dinosaur genus Poekilopleuron as Poicilopleuron valens. He later decided it deserved its own genus, Antrodemus.
Allosaurus itself is based on YPM 1930, a small collection of fragmentary bones including parts of three vertebrae, a rib fragment, a tooth, a toe bone, and (most useful for later discussions) the shaft of the right humerus (upper arm). Othniel Charles Marsh gave these remains the formal name Allosaurus fragilis in 1877. Allosaurus comes from the Greek words /, meaning "strange" or "different", and /, meaning "lizard" or "reptile". It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at the time of its discovery. The species epithet fragilis is Latin for "fragile", referring to lightening features in the vertebrae. The bones were collected from the Morrison Formation of Garden Park, north of Cañon City. O. C. Marsh and Edward Drinker Cope, who were in scientific competition with each other, went on to coin several other genera based on similarly sparse material that would later figure in the taxonomy of Allosaurus. These include Marsh's Creosaurus and Labrosaurus, as well as Cope's Epanterias. | Allosaurus | Wikipedia | 375 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In their haste, Cope and Marsh did not always follow up on their discoveries (or, more commonly, those made by their subordinates). For example, after the discovery by Benjamin Mudge of the type specimen of Allosaurus in Colorado, Marsh elected to concentrate work in Wyoming. When work resumed at Garden Park in 1883, M. P. Felch found an almost complete Allosaurus and several partial skeletons. In addition, one of Cope's collectors, H. F. Hubbell, found a specimen in the Como Bluff area of Wyoming in 1879, but apparently did not mention its completeness and Cope never unpacked it. Upon unpacking it in 1903 (several years after Cope had died), it was found to be one of the most complete theropod specimens then known and the skeleton, now cataloged as AMNH 5753, was put on public view in 1908. This is the well-known mount poised over a partial Apatosaurus skeleton as if scavenging it, illustrated as such in a painting by Charles R. Knight. Although notable as the first free-standing mount of a theropod dinosaur and often illustrated and photographed, it has never been scientifically described.
The multiplicity of early names complicated later research, with the situation compounded by the terse descriptions provided by Marsh and Cope. Even at the time, authors such as Samuel Wendell Williston suggested that too many names had been coined. For example, Williston pointed out in 1901 that Marsh had never been able to adequately distinguish Allosaurus from Creosaurus. The most influential early attempt to sort out the convoluted situation was produced by Charles W. Gilmore in 1920. He came to the conclusion that the tail vertebra named Antrodemus by Leidy was indistinguishable from those of Allosaurus and that Antrodemus should be the preferred name because, as the older name, it had priority. Antrodemus became the accepted name for this familiar genus for over 50 years, until James Henry Madsen published on the Cleveland-Lloyd specimens and concluded that Allosaurus should be used because Antrodemus was based on material with poor, if any, diagnostic features and locality information. For example, the geological formation that the single bone of Antrodemus came from is unknown. "Antrodemus" has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen.
Cleveland-Lloyd discoveries | Allosaurus | Wikipedia | 504 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Although sporadic work at what became known as the Cleveland-Lloyd Dinosaur Quarry in Emery County, Utah, had taken place as early as 1927 and the fossil site itself described by William L. Stokes in 1945, major operations did not begin there until 1960. Under a cooperative effort involving nearly 40 institutions, thousands of bones were recovered between 1960 and 1965, led by James Henry Madsen. The quarry is notable for the predominance of Allosaurus remains, the condition of the specimens, and the lack of scientific resolution on how it came to be. The majority of bones belong to the large theropod Allosaurus fragilis (it is estimated that the remains of at least 46 A. fragilis have been found there, out of at a minimum 73 dinosaurs) and the fossils found there are disarticulated and well-mixed. Nearly a dozen scientific papers have been written on the taphonomy of the site, suggesting numerous mutually exclusive explanations for how it may have formed. Suggestions have ranged from animals getting stuck in a bog, becoming trapped in deep mud, falling victim to drought-induced mortality around a waterhole, and getting trapped in a spring-fed pond or seep. Regardless of the actual cause, the great quantity of well-preserved Allosaurus remains has allowed this genus to be known in great detail, making it among the best-known of all theropods. Skeletal remains from the quarry pertain to individuals of almost all ages and sizes, from less than to long, and the disarticulation is an advantage for describing bones usually found fused. Due to being one of Utah's two fossil quarries where numerous Allosaurus specimens have been discovered, Allosaurus was designated as the state fossil of Utah in 1988.
Modern study
The period since Madsen's monograph has been marked by a great expansion in studies dealing with topics concerning Allosaurus in life (paleobiological and paleoecological topics). Such studies have covered topics including skeletal variation, growth, skull construction, hunting methods, the brain, and the possibility of gregarious living and parental care. Reanalysis of old material (particularly of large 'allosaur' specimens), new discoveries in Portugal, and several very complete new specimens have also contributed to the growing knowledge base.
"Big Al" and "Big Al II" | Allosaurus | Wikipedia | 471 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1991, "Big Al" (MOR 693), a 95% complete, partially articulated specimen of Allosaurus was discovered, measuring about long. MOR 693 was excavated near Shell, Wyoming, by a joint Museum of the Rockies and University of Wyoming Geological Museum team. This skeleton was discovered by a Swiss team, led by Kirby Siber. Chure and Loewen in 2020 identified the individual as a representative of the species A. jimmadseni. In 1996, the same team discovered a second Allosaurus, "Big Al II". This specimen, the best preserved skeleton of its kind to date, is also referred to A. jimmadseni.
The completeness, preservation, and scientific importance of this skeleton gave "Big Al" its name. The individual itself was below the average size for Allosaurus fragilis, as it was a subadult estimated at only 87% grown. The specimen was described by Breithaupt in 1996. Nineteen of its bones were broken or showed signs of serious infection, which may have contributed to "Big Al's" death. Pathologic bones included five ribs, five vertebrae, and four bones of the feet. Several of its damaged bones showed signs of osteomyelitis, a severe bone infection. A particular problem for the living animal was infection and trauma to the right foot that probably affected movement and may have also predisposed the other foot to injury because of a change in gait. "Big Al" had an infection on the first phalanx on the third toe that was afflicted by an involucrum. The infection was long-lived, perhaps up to six months. "Big Al II" is also known to have multiple injuries.
Portuguese discoveries | Allosaurus | Wikipedia | 358 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1988, during construction works of a warehouse, a skeleton of a large theropod was discovered near the village of Andrés, Leiria District, Portugal. The Andrés quarry is included in the Bombarral Formation ("Grés Superiores"). The lower part of this formation is diachronic with the Alcobaça Formation in the northen Lusitanian Basin, and is dated to the Early Tithonian. This specimen was reported in 1999 as the first occurrence of Allosaurus fragilis outside North America. The specimen, labelled MNHNUL/AND.001, is deposited in the National Museum of Natural History and Science, Lisbon. It consists of a partial skeleton, composed of an incomplete right quadrate, several vertebrae and chevrons, several dorsal ribs and gastralia, a partial pelvis, most of the hind limbs and several indeterminate fragments. In 2003, Miguel Telles Antunes and Octávio Mateus published a review of the dinosaurs from Portugal, where they assigned the Andrés specimen to Allosaurus sp.
The Guimarota coal mine in Leiria, Portugal, produced plenty of remains of micro-vertebrates while it was being explored. The Guimarota beds belong to the Alcobaça Formation, and are dated of the Late Kimmeridgian. In 2005, Oliver Rauhut and Regina Fechner describe the right maxilla of a juvenile theropod (IPFUB Gui Th 4) from the Guimarota mine, that was stored in the collections of the Institute of Geological Sciences of the Free University of Berlin. They attribute the maxilla to Allosaurus sp. based on the large maxillary fenestra and coeval presence of the other Allosaurus specimens. This specimen allowed the authors to conclude that the development of paranasal pneumacity in theropods is heterochronic, with juveniles having more pronouced pneumaticity than adults.
In 2006, a new species of Allosaurus, A. europaeus, was reported based a specimen found in a beach near Vale Frades, Lourinhã, Portugal. The specimen, labelled ML415, is deposited in the Lourinhã Museum, and consists of a partial skull, three cervical vertebrae and cervical ribs. It was found in rocks of the Praia Azul Member of the Lourinhã Formation, which in that sector is dated to the Early Tithonian. | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2005, the Andrés quarry was reactivated for further prospection, which yielded remains of a diverse vertebrate fauna and new Allosaurus remains. These new remains (such as a partial right frontal, MNHNUL/AND.001/062), along with further preparation of the original Andrés specimen, allowed for a more detailed comparison with other Allosaurus species. The authors concluded that the Andrés specimen is compatible with the diagnosis of A. fragilis, and also disputed the attribution of the Vale Frades specimen to a new species, claiming that the autapomorphies proposed in the diagnosis of A. europaeus can be explained by individual variation. In 2010, new Allosaurus elements from the Andrés quarry are reported, including new cranial remains such as a right quadrate-quadratojudal, two lacrimals, a right dentary, a right frontal, the posterior end of the right mandible and a complete braincase. A second complete left ilium suggests the presence of a second Allosaurus individual in the quarry, larger than the first. The authors once again claim that A. europaeus should be considered a nomen dubium until a more detailed description of the Vale Frades specimen is published. | Allosaurus | Wikipedia | 254 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A detailed description of the remains of the Andrés specimen was published on the doctoral thesis of Elisabete Malafaia. The remains were collected between 1988 and 2010, and include cranial elements (such as the maxilla, nasal, lacrimals, prefrontal, postorbitals, frontals, palatines, quadrate, quadratojugal, squamosal, vomer, braincase, articular, surangulars, prearticular, angulars, supradentary and coronoid, isolated mesial and lateral teeth) and postcranial elements (intercentrum of the atlas, dorsal, sacral and caudal vertebrae, cervical and dorsal ribs, chevrons, coracoid, ilium, pubes, femora, tibiae, fibulae, astragalus and calcaneum, distal tarsal III, second, tird, and fourth metatarsals, and several phalanges). Duplicate elements reported in the thesis include the previously mentioned left ilium, a fragmentary pubic peduncle in articulation with the pubes, and a right frontal, caudal vertebra, and pedal phalanges of a third much smaller individual. The author claims that the Andrés specimens present noticeable differences with both A. fragilis and the type specimen of A. europaeus, but tentatively assigns it to Allosaurus cf. europaeus, pending the discovery of more specimens that allow the comparison between the two.
In 2024, Burigo and Mateus publish a redescription and revised diagnosis of the Vale Frades specimen. The authors report new elements, such as the atlas-axis, coronoid, new teeth and rib fragments, and confirm the validity of the species. A specimen-level phylogenetic analysis using scored cranial characters was performed. The authors claim that the Andrés specimen is attributable to A. europaeus, and that A. europaeus is more closely related to A. jimmadsenni than to A. fragilis.
Species | Allosaurus | Wikipedia | 430 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Seven species of Allosaurus have been named: A. anax, A. amplus, A. atrox, A. europaeus, the type species A. fragilis, A. jimmadseni and A. lucasi. Among these (excluding A. anax, which was named in 2024), Daniel Chure and Mark Loewen in 2020 only recognized the species A. fragilis, A. europaeus, and the newly-named A. jimmadseni as being valid species. Some studies have suggested that A. europaeus does not show any unique characters compared to the North American species, though other authors have suggested that the species is valid and has a number of distinguishing characters.
A. fragilis is the type species and was named by Marsh in 1877. It is known from the remains of at least 60 individuals, all found in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming. Details of the humerus (upper arm) of A. fragilis have been used as diagnostic among Morrison theropods, but A. jimmadseni indicates that this is no longer the case at the species level.
A. jimmadseni has been scientifically described based on two nearly complete skeletons. The first specimen to wear the identification was unearthed in Dinosaur National Monument in northeastern Utah, with the original "Big Al" individual subsequently recognized as belonging to the same species. This species differs from A. fragilis in several anatomical details, including a jugal (cheekbone) with a straight lower margin. Fossils are confined to the Salt Wash Member of the Morrison Formation, with A. fragilis only found in the higher Brushy Basin Member. The specific name jimmadseni is named in honor of Madsen, for his contributions to the taxonomy of the genus, notably for his 1976 work. | Allosaurus | Wikipedia | 408 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A. fragilis, A. jimmadseni, A. anax, A. amplus, and A. lucasi are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah and Wyoming. A. fragilis is regarded as the most common, known from the remains of at least 60 individuals. For a while in the late 1980s and early 1990s, it was common to recognize A. fragilis as the short-snouted species, with the long-snouted taxon being A. atrox. However, subsequent analysis of specimens from the Cleveland-Lloyd Dinosaur Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation. A study of skull elements from the Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns and the proposed differentiation of A. jimmadseni based on the shape of the jugal. A. anax was described and named in 2024 from several fossils representing various skeleton parts, the holotype being a postorbital numbered as OMNH 1771. This species is characterized by the lack of rugose ornamentation on the postorbital, the dorsal vertebrae with hourglass-shaped centra and pneumatic foramina, and other features of the postorbital, cervical vertebrae, and fibula. The specific name comes from the Ancient Greek ἄναξ (anax, "king", "lord" or "tribal chief"), and is intended to be an updated reference to the now dubious saurischian genus Saurophaganax, to which the fossils were previously attributed. | Allosaurus | Wikipedia | 386 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Allosaurus material from Portugal has a controversial taxonomic research history. The Andrés Allosaurus specimens, consisting of very complete cranial and post-cranial remains, have been attributed to A. fragilis, A. sp, A. europaeus and A. cf. europaeus. The Vale Frades Allosaurus, consisting of a partial skull and cervical vertebrae and ribs, is the type specimen of A. europaeus, although the validity of that species has been previously questioned. In 2024, a revised diagnosis of A. europaeus was published, confirming the validity of the species. The specific affinities of the Andrés specimens are still unclear.
The issue of species and potential synonyms was historically complicated by the type specimen of Allosaurus fragilis (YPM 1930) being extremely fragmentary, consisting of a few incomplete vertebrae, limb fragments, rib fragments, and a single tooth. Because of this, several scientists have interpreted the type specimen as potentially dubious, meaning the genus Allosaurus itself or at least the species A. fragilis would be a nomen dubium ("dubious name", based on a specimen too incomplete to compare to other specimens or to classify). To address this situation, Gregory S. Paul and Kenneth Carpenter (2010) submitted a petition to the ICZN to have the name A. fragilis officially transferred to the more complete specimen USNM4734 (as a neotype), a decision that was ratified by the ICZN on December 29, 2023.
Teeth of indeterminate species of Allosaurus have been reported from Tönniesberg and Kahlberg in Saxony, Germany, dating to the upper Kimmeridigian.
Synonyms
Creosaurus, Epanterias, and Labrosaurus are regarded as junior synonyms of Allosaurus. Most of the species that are regarded as synonyms of A. fragilis, or that were misassigned to the genus, are obscure and based on very scrappy remains. One exception is Labrosaurus ferox, named in 1884 by Marsh for an oddly formed partial lower jaw, with a prominent gap in the tooth row at the tip of the jaw, and a rear section greatly expanded and turned down. Later researchers suggested that the bone was pathologic, showing an injury to the living animal, and that part of the unusual form of the rear of the bone was due to plaster reconstruction. It is now regarded as an example of A. fragilis. | Allosaurus | Wikipedia | 507 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In his 1988 book, Predatory Dinosaurs of the World, the freelance artist & author Gregory S. Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox, as well as not being a different sex due to rarity. Allosaurus atrox was originally named by Marsh in 1878 as the type species of its own genus, Creosaurus, and is based on YPM 1890, an assortment of bones that includes a couple of pieces of the skull, portions of nine tail vertebrae, two hip vertebrae, an ilium, and ankle and foot bones. Although the idea of two common Morrison allosaur species was followed in some semi-technical and popular works, the 2000 thesis on Allosauridae noted that Charles Gilmore mistakenly reconstructed USNM 4734 as having a shorter skull than the specimens referred by Paul to atrox, refuting supposed differences between USNM 4734 and putative A. atrox specimens like DINO 2560, AMNH 600, and AMNH 666.
"Allosaurus agilis", seen in Zittel, 1887, and Osborn, 1912, is a typographical error for A. fragilis. "Allosaurus ferox" is a typographical error by Marsh for A. fragilis in a figure caption for the partial skull YPM 1893 and YPM 1893 has been treated as a specimen of A fragilis. Likewise, "Labrosaurus fragilis" is a typographical error by Marsh (1896) for Labrosaurus ferox. "A. whitei" is a nomen nudum coined by Pickering in 1996 for the complete Allosaurus specimens that Paul referred to A. atrox.
"Madsenius" was coined by David Lambert in 1990, being based on remains from Dinosaur National Monument assigned to Allosaurus or Creosaurus (a synonym of Allosaurus), and was to be described by paleontologist Robert Bakker as "Madsenius trux". However, "Madsenius" is now seen as yet another synonym of Allosaurus because Bakker's action was predicated upon the false assumption of USNM 4734 being distinct from long-snouted Allosaurus due to errors in Gilmore's 1920 reconstruction of USNM 4734. | Allosaurus | Wikipedia | 486 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
"Wyomingraptor" was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic. The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum. However, there has been no official description of the remains and "Wyomingraptor" has been dismissed as a nomen nudum, with the remains referable to Allosaurus.
Formerly assigned species and fossils
Several species initially classified within or referred to Allosaurus do not belong within the genus. A. medius was named by Marsh in 1888 for various specimens from the Early Cretaceous Arundel Formation of Maryland, although most of the remains were removed by Richard Swann Lull to the new ornithopod species Dryosaurus grandis, except for a tooth. It was transferred to Antrodemus by Oliver Hay in 1902, but Hay later clarified that this was an inexplicable error on his part. Gilmore considered the tooth nondiagnostic but transferred it to Dryptosaurus, as D. medius. The referral was not accepted in the most recent review of basal tetanurans, and Allosaurus medius was simply listed as a dubious species of theropod. It may be closely related to Acrocanthosaurus.
Allosaurus valens is a new combination for Antrodemus valens used by Friedrich von Huene in 1932; Antrodemus valens itself may also pertain to Allosaurus fragilis, as Gilmore suggested in 1920.
A. lucaris, another Marsh name, was given to a partial skeleton in 1878. He later decided it warranted its own genus, Labrosaurus, but this has not been accepted, and A. lucaris is also regarded as another specimen of A. fragilis. Allosaurus lucaris, is known mostly from vertebrae, sharing characters with Allosaurus. Paul and Carpenter stated that the type specimen of this species, YPM 1931, was from a younger age than Allosaurus, and might represent a different genus. However, they found that the specimen was undiagnostic, and thus A. lucaris was a nomen dubium. | Allosaurus | Wikipedia | 440 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus sibiricus was described in 1914 by A. N. Riabinin on the basis of a bone, later identified as a partial fourth metatarsal, from the Early Cretaceous of Buryatia, Russia. It was transferred to Chilantaisaurus in 1990, but is now considered a nomen dubium indeterminate beyond Theropoda.
Allosaurus meriani was a new combination by George Olshevsky for Megalosaurus meriani Greppin, 1870, based on a tooth from the Late Jurassic of Switzerland. However, a recent overview of Ceratosaurus included it in Ceratosaurus sp.
Apatodon mirus, based on a scrap of vertebra Marsh first thought to be a mammalian jaw, has been listed as a synonym of Allosaurus fragilis. However, it was considered indeterminate beyond Dinosauria by Chure, and Mickey Mortimer believes that the synonymy of Apatodon with Allosaurus was due to correspondence to Ralph Molnar by John McIntosh, whereby the latter reportedly found a paper saying that Othniel Charles Marsh admitted that the Apatodon holotype was actually an allosaurid dorsal vertebra.
A. amplexus was named by Gregory S. Paul for giant Morrison allosaur remains, and included in his conception Saurophagus maximus (later Saurophaganax). A. amplexus was originally coined by Cope in 1878 as the type species of his new genus Epanterias, and is based on what is now AMNH 5767, parts of three vertebrae, a coracoid, and a metatarsal. Following Paul's work, this species has been accepted as a synonym of A. fragilis. A 2010 study by Paul and Kenneth Carpenter, however, indicates that Epanterias is temporally younger than the A. fragilis type specimen, so it is a separate species at minimum. | Allosaurus | Wikipedia | 394 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A. maximus was a new combination by David K. Smith for Chure's Saurophaganax maximus, a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma. These remains had been known as Saurophagus, but that name was already in use, leading Chure to propose a substitute. Smith, in his 1998 analysis of variation, concluded that S. maximus was not different enough from Allosaurus to be a separate genus, but did warrant its own species, A. maximus. This reassignment was rejected in a review of basal tetanurans. A 2024 reassessment of fossil material assigned to Saurophaganax suggested that the holotype neural arch of this taxon could not confidently be assigned to a theropod, but that it exhibited some similarities to sauropods. Other Saurophaganax bones could be referred to diplodocid sauropods. As such, the researchers assigned the remaining theropod bones to a new species of Allosaurus, A. anax.
There are also several species left over from the synonymizations of Creosaurus and Labrosaurus with Allosaurus. Creosaurus potens was named by Lull in 1911 for a vertebra from the Early Cretaceous of Maryland. It is now regarded as a dubious theropod. Labrosaurus stechowi, described in 1920 by Janensch based on isolated Ceratosaurus-like teeth from the Tendaguru beds of Tanzania, was listed by Donald F. Glut as a species of Allosaurus, is now considered a dubious ceratosaurian related to Ceratosaurus. L. sulcatus, named by Marsh in 1896 for a Morrison theropod tooth, which like L. stechowi is now regarded as a dubious Ceratosaurus-like ceratosaur.
A. tendagurensis was named in 1925 by Werner Janensch for a partial shin (MB.R.3620) found in the Kimmeridgian-age Tendaguru Formation in Mtwara, Tanzania. Although tabulated as a tentatively valid species of Allosaurus in the second edition of the Dinosauria, subsequent studies place it as indeterminate beyond Tetanurae, either a carcharodontosaurian or megalosaurid. Although obscure, it was a large theropod, possibly around long and in weight. | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Kurzanov and colleagues in 2003 designated six teeth from Siberia as Allosaurus sp. (meaning the authors found the specimens to be most like those of Allosaurus, but did not or could not assign a species to them). They were reclassified as an indeterminate theropod. Also, reports of Allosaurus in Shanxi, China go back to at least 1982. These were interpreted as Torvosaurus remains in 2012.
An astragalus (ankle bone) thought to belong to a species of Allosaurus was found at Cape Paterson, Victoria in Early Cretaceous beds in southeastern Australia. It was thought to provide evidence that Australia was a refugium for animals that had gone extinct elsewhere. This identification was challenged by Samuel Welles, who thought it more resembled that of an ornithomimid, but the original authors defended their identification. With fifteen years of new specimens and research to look at, Daniel Chure reexamined the bone and found that it was not Allosaurus, but could represent an allosauroid. Similarly, Yoichi Azuma and Phil Currie, in their description of Fukuiraptor, noted that the bone closely resembled that of their new genus. This specimen is sometimes referred to as "Allosaurus robustus", an informal museum name. It likely belonged to something similar to Australovenator, although one study considered it to belong to an abelisaur.
Description | Allosaurus | Wikipedia | 289 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus was a typical large theropod, having a massive skull on a short neck, a long, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of and mass of , with the largest definitive Allosaurus specimen (AMNH 680) estimated at long, with an estimated weight of . In his 1976 monograph on Allosaurus, James H. Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of . As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between , , and approximately for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that is reasonable for large adults of A. fragilis, but that is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed "Big Al", since assigned to the species Allosaurus jimmadseni, researchers using computer modeling arrived at a best estimate of for the individual, but by varying parameters they found a range from approximately to approximately . A separate computational project estimated the adaptive optimum body mass in Allosaurus to be ~2,345 kg. A. europaeus has been measured up to in length and in body mass.
Several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. The dubious genus Saurophaganax (OMNH 1708) was estimated to reach around in length, and its single species was sometimes included in the genus Allosaurus as Allosaurus maximus. However, a 2024 study concluded that some material assigned to Saurophaganax actually belonged to a diplodocid sauropod with the material confidently assigned to Allosauridae belonging to a new species of Allosaurus, A. anax, and the body mass of this species was tentatively estimated around based on fragmentary material. Another potential specimen of Allosaurus, once assigned to the genus Epanterias (AMNH 5767), may have measured in length. A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico; this large allosaurid was suggested to be a potential specimen of Saurophaganax prior to this taxon's 2024 reassessment. | Allosaurus | Wikipedia | 478 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
David K. Smith, examining Allosaurus fossils by quarry, found that the Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites. A later study by Smith incorporating Garden Park (Colorado) and Dinosaur National Monument (Utah) specimens found no justification for multiple species based on skeletal variation; skull variation was most common and was gradational, suggesting individual variation was responsible. Further work on size-related variation again found no consistent differences, although the Dry Mesa material tended to clump together on the basis of the astragalus, an ankle bone. Kenneth Carpenter, using skull elements from the Cleveland-Lloyd site, found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the horns, and the proposed differentiation of A. jimmadseni based on the shape of the jugal. A study published by Motani et al., in 2020 suggests that Allosaurus was also sexually dimorphic in the width of the femur's head against its length.
Skull
The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size. Paleontologist Gregory S. Paul gives a length of for a skull belonging to an individual he estimates at long. Each premaxilla (the bones that formed the tip of the snout) held five teeth with D-shaped cross-sections, and each maxilla (the main tooth-bearing bones in the upper jaw) had between 14 and 17 teeth; the number of teeth does not exactly correspond to the size of the bone. Each dentary (the tooth-bearing bone of the lower jaw) had between 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, and more curved toward the back of the skull. All of the teeth had saw-like edges. They were shed easily, and were replaced continually, making them common fossils. Its skull was light, robust and equipped with dozens of sharp, serrated teeth. | Allosaurus | Wikipedia | 437 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The skull had a pair of horns above and in front of the eyes. These horns were composed of extensions of the lacrimal bones, and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns. The horns were probably covered in a keratin sheath and may have had a variety of functions, including acting as sunshades for the eyes, being used for display, and being used in combat against other members of the same species (although they were fragile). There was a ridge along the back of the skull roof for muscle attachment, as is also seen in tyrannosaurids.
Inside the lacrimal bones were depressions that may have held glands, such as salt glands. Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus; they may have been related to the sense of smell, perhaps holding something like Jacobson's organs. The roof of the braincase was thin, perhaps to improve thermoregulation for the brain. The skull and lower jaws had joints that permitted motion within these units. In the lower jaws, the bones of the front and back halves loosely articulated, permitting the jaws to bow outward and increasing the animal's gape. The braincase and frontals may also have had a joint.
Postcranial skeleton | Allosaurus | Wikipedia | 289 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus had nine vertebrae in the neck, 14 in the back, and five in the sacrum supporting the hips. The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50, while Gregory S. Paul considered that to be too many and suggested 45 or less. There were hollow spaces in the neck and anterior back vertebrae. Such spaces, which are also found in modern theropods (that is, the birds), are interpreted as having held air sacs used in respiration. The rib cage was broad, giving it a barrel chest, especially in comparison to less derived theropods like Ceratosaurus. Allosaurus had gastralia (belly ribs), but these are not common findings, and they may have ossified poorly. In one published case, the gastralia show evidence of injury during life. A furcula (wishbone) was also present, but has only been recognized since 1996; in some cases furculae were confused with gastralia. The ilium, the main hip bone, was massive, and the pubic bone had a prominent foot that may have been used for both muscle attachment and as a prop for resting the body on the ground. Madsen noted that in about half of the individuals from the Cleveland-Lloyd Dinosaur Quarry, independent of size, the pubes had not fused to each other at their foot ends. He suggested that this was a sexual characteristic, with females lacking fused bones to make egg-laying easier. This proposal has not attracted further attention, however. | Allosaurus | Wikipedia | 316 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The forelimbs of Allosaurus were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults) and had three fingers per hand, tipped with large, strongly curved and pointed claws. The arms were powerful, and the forearm was somewhat shorter than the upper arm (1:1.2 ulna/humerus ratio). The wrist had a version of the semilunate carpal also found in more derived theropods like maniraptorans. Of the three fingers, the innermost (or thumb) was the largest, and diverged from the others. The phalangeal formula is 2-3-4-0-0, meaning that the innermost finger (phalange) has two bones, the next has three, and the third finger has four. The legs were not as long or suited for speed as those of tyrannosaurids, and the claws of the toes were less developed and more hoof-like than those of earlier theropods. Each foot had three weight-bearing toes and an inner dewclaw, which Madsen suggested could have been used for grasping in juveniles. There was also what is interpreted as the splint-like remnant of a fifth (outermost) metatarsal, perhaps used as a lever between the Achilles tendon and foot.
Skin
Skin impressions from Allosaurus have been described. One impression, from a juvenile specimen, measures 30 cm² and is associated with the anterior dorsal ribs/pectoral region. The impression shows small scales measuring 1–3 mm in diameter. A skin impression from the "Big Al Two" specimen, associated with the base of the tail, measures 20 cm x 20 cm and shows large scales measuring up to 2 cm in diameter. However, it has been noted that these scales are more similar to those of sauropods, and due to the presence of non-theropod remains associated with the tail of "Big Al Two" there is a possibility that this skin impression is not from Allosaurus.
Another Allosaurus fossil features a skin impression from the mandible, showing scales measuring 1–2 mm in diameter. The same fossil also preserves skin measuring 20 x 20 cm from the ventral side of the neck, showing scutate scales measuring 0.5 cm wide and 11 cm long. A small skin impression from an Allosaurus skull has been reported but never described.
Classification | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventually became a wastebasket taxon. This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen's 1976 monograph. Major publications using the name "Megalosauridae" instead of "Allosauridae" include Gilmore, 1920, von Huene, 1926, Romer, 1956 and 1966, Steel, 1970, and Walker, 1964.
Following the publication of Madsen's influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi-technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to Allosaurus included Indosaurus, Piatnitzkysaurus, Piveteausaurus, Yangchuanosaurus, Acrocanthosaurus, Chilantaisaurus, Compsosuchus, Stokesosaurus, and Szechuanosaurus. Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus, are members of closely related families.
Below is a cladogram based on the analysis of Benson et al. in 2010. | Allosaurus | Wikipedia | 371 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosauridae is one of four families in Allosauroidea; the other three are Neovenatoridae, Carcharodontosauridae and Sinraptoridae. Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one example being Gregory S. Paul's Predatory Dinosaurs of the World, but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria. Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review. Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus. Some reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus.
The controversial Saurophaganax, initially recognized as a large Allosaurus-like theropod, has had a controversial taxonomic history. In 2019, Rauhut and Pol noted that its taxonomic placement within Allosauroidea is unstable, being recovered as a sister taxon of Metriacanthosauridae or Allosauria, or even as the basalmost carcharodontosaurian. In 2024, Saurophaganax was reassessed as a dubious, chimeric taxon with the holotype being so fragmentary that it could only be confidently referred to the Saurischia, and some specimens more likely belonging to a diplodocid sauropod.
Paleobiology
Life history
The wealth of Allosaurus fossils, from nearly all ages of individuals, allows scientists to study how the animal grew and how long its lifespan may have been. Remains may reach as far back in the lifespan as eggs—crushed eggs from Colorado have been suggested as those of Allosaurus. Based on histological analysis of limb bones, bone deposition appears to stop at around 22 to 28 years, which is comparable to that of other large theropods like Tyrannosaurus. From the same analysis, its maximum growth appears to have been at age 15, with an estimated growth rate of about 150 kilograms (330 lb) per year. | Allosaurus | Wikipedia | 486 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Medullary bone tissue (endosteally derived, ephemeral, mineralization located inside the medulla of the long bones in gravid female birds) has been reported in at least one Allosaurus specimen, a shin bone from the Cleveland-Lloyd Quarry. Today, this bone tissue is only formed in female birds that are laying eggs, as it is used to supply calcium to shells. Its presence in the Allosaurus individual has been used to establish sex and show it had reached reproductive age. However, other studies have called into question some cases of medullary bone in dinosaurs, including this Allosaurus individual. Data from extant birds suggested that the medullary bone in this Allosaurus individual may have been the result of a bone pathology instead. However, with the confirmation of medullary tissue indicating sex in a specimen of Tyrannosaurus, it may be possible to ascertain whether or not the Allosaurus in question was indeed female.
The discovery of a juvenile specimen with a nearly complete hindlimb shows that the legs were relatively longer in juveniles, and the lower segments of the leg (shin and foot) were relatively longer than the thigh. These differences suggest that younger Allosaurus were faster and had different hunting strategies than adults, perhaps chasing small prey as juveniles, then becoming ambush hunters of large prey upon adulthood. The thigh bone became thicker and wider during growth, and the cross-section less circular, as muscle attachments shifted, muscles became shorter, and the growth of the leg slowed. These changes imply that juvenile legs has less predictable stresses compared with adults, which would have moved with more regular forward progression. Conversely, the skull bones appear to have generally grown isometrically, increasing in size without changing in proportion.
Feeding | Allosaurus | Wikipedia | 353 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Most paleontologists accept Allosaurus as an active predator of large animals. There is dramatic evidence for allosaur attacks on Stegosaurus, including an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike, and a Stegosaurus neck plate with a U-shaped wound that correlates well with an Allosaurus snout. Sauropods seem to be likely candidates as both live prey and as objects of scavenging, based on the presence of scrapings on sauropod bones fitting allosaur teeth well and the presence of shed allosaur teeth with sauropod bones. However, as Gregory Paul noted in 1988, Allosaurus was probably not a predator of fully grown sauropods, unless it hunted in packs, as it had a modestly sized skull and relatively small teeth, and was greatly outweighed by contemporaneous sauropods. Another possibility is that it preferred to hunt juveniles instead of fully grown adults. Research in the 1990s and the first decade of the 21st century may have found other solutions to this question. Robert T. Bakker, comparing Allosaurus to Cenozoic saber-toothed carnivorous mammals, found similar adaptations, such as a reduction of jaw muscles and increase in neck muscles, and the ability to open the jaws extremely wide. Although Allosaurus did not have saber teeth, Bakker suggested another mode of attack that would have used such neck and jaw adaptations: the short teeth in effect became small serrations on a saw-like cutting edge running the length of the upper jaw, which would have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim. | Allosaurus | Wikipedia | 352 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Similar conclusions were drawn by another study using finite element analysis on an Allosaurus skull. According to their biomechanical analysis, the skull was very strong but had a relatively small bite force. By using jaw muscles only, it could produce a bite force of 805 to 8,724 N, but the skull could withstand nearly 55,500 N of vertical force against the tooth row. The authors suggested that Allosaurus used its skull like a machete against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones, unlike Tyrannosaurus, which is thought to have been capable of damaging bones. They also suggested that the architecture of the skull could have permitted the use of different strategies against different prey; the skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurids and sauropods. Their interpretations were challenged by other researchers, who found no modern analogs to a hatchet attack and considered it more likely that the skull was strong to compensate for its open construction when absorbing the stresses from struggling prey. The original authors noted that Allosaurus itself has no modern equivalent, that the tooth row is well-suited to such an attack, and that articulations in the skull cited by their detractors as problematic actually helped protect the palate and lessen stress. Another possibility for handling large prey is that theropods like Allosaurus were "flesh grazers" which could take bites of flesh out of living sauropods that were sufficient to sustain the predator so it would not have needed to expend the effort to kill the prey outright. This strategy would also potentially have allowed the prey to recover and be fed upon in a similar way later. An additional suggestion notes that ornithopods were the most common available dinosaurian prey, and that Allosaurus may have subdued them by using an attack similar to that of modern big cats: grasping the prey with their forelimbs, and then making multiple bites on the throat to crush the trachea. This is compatible with other evidence that the forelimbs were strong and capable of restraining prey. Studies done by Stephen Lautenschager et al. from the University of Bristol also indicate Allosaurus could open its jaws quite wide and sustain considerable muscle force | Allosaurus | Wikipedia | 483 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
When compared with Tyrannosaurus and the therizinosaurid Erlikosaurus in the same study, it was found that Allosaurus had a wider gape than either; the animal was capable of opening its jaws to a 92-degree angle at maximum. The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider jaw gapes than herbivores | Allosaurus | Wikipedia | 79 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A biomechanical study published in 2013 by Eric Snively and colleagues found that Allosaurus had an unusually low attachment point on the skull for the longissimus capitis superficialis neck muscle compared to other theropods such as Tyrannosaurus. This would have allowed the animal to make rapid and forceful vertical movements with the skull. The authors found that vertical strikes as proposed by Bakker and Rayfield are consistent with the animal's capabilities. They also found that the animal probably processed carcasses by vertical movements in a similar manner to falcons, such as kestrels: the animal could have gripped prey with the skull and feet, then pulled back and up to remove flesh. This differs from the prey-handling envisioned for tyrannosaurids, which probably tore flesh with lateral shakes of the skull, similar to crocodilians. In addition, Allosaurus was able to "move its head and neck around relatively rapidly and with considerable control", at the cost of power.
Other aspects of feeding include the eyes, arms, and legs. The shape of the skull of Allosaurus limited potential binocular vision to 20° of width, slightly less than that of modern crocodilians. As with crocodilians, this may have been enough to judge prey distance and time attacks. The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close, and the articulation of the claws suggests that they could have been used to hook things. Finally, the top speed of Allosaurus has been estimated at per hour.
A paper on the cranio-dental morphology of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely, reinterpreting the unusually wide gape as an adaptation to allow Allosaurus to deliver a muscle-driven bite to large prey, with the weaker jaw muscles being a trade-off to allow for the widened gape. | Allosaurus | Wikipedia | 402 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Sauropod carrion may also have been important to large theropods in the Morrison Formation. Forensic techniques indicate that sauropod carcasses were targeted by Allosaurus at all stages of decomposition, indicating that late-stage decay pathogens were not a significant deterrent. A survey of sauropod bones from the Morrison Formation also reported widespread bite marks on sauropod bones in low-economy regions, which suggests that large theropods scavenged large sauropods when available, with the scarcity of such bite marks on the remains of smaller bones being potentially attributable to much more complete consumption of smaller or adolescent sauropods and on ornithischians, which would have been more commonly taken as live prey. A single dead adult Barosaurus or Brachiosaurus would have had enough calories to sustain multiple large theropods for weeks or months, though the vast majority of the Morrison's sauropod fossil record consisted of much smaller-bodied taxa such as Camarasaurus lentus or Diplodocus.
It has also been argued that disabled individuals such as Big Al and Big Al II were physically incapable of hunting due to their numerous injuries but were able to survive nonetheless as scavengers of giant sauropod-falls, Interestingly, a recent review of paleopathologies in theropods may support this conclusion. The researchers found a positive association between allosaurids and fractures to the appendicular skeleton, while tyrannosaurs had a statistically negative association with these types of injuries. The fact that allosaurs were more likely to survive and heal even when severe fractures limited their locomotion abilities can be explained, in part, by different resource accessibility paradigms for the two groups, as allosauroids generally lived in sauropod-inhabited ecosystems, some of which, including the Morrison, have been interpreted as arid and highly water-stressed environments; however, the water-stressed nature of the Morrison has been heavily criticized in several more recent works on the basis of fossil evidence for the presence of extensive forest cover and aquatic ecosystems.
Social behavior | Allosaurus | Wikipedia | 430 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups.
Such a depiction is common in semitechnical and popular dinosaur literature. Robert T. Bakker has extended social behavior to parental care, and has interpreted shed allosaur teeth and chewed bones of large prey animals as evidence that adult allosaurs brought food to lairs for their young to eat until they were grown, and prevented other carnivores from scavenging on the food. However, there is actually little evidence of gregarious behavior in theropods, and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia and bite wounds to skulls (the pathologic lower jaw named Labrosaurus ferox is one such possible example). Such head-biting may have been a way to establish dominance in a pack or to settle territorial disputes. | Allosaurus | Wikipedia | 192 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Although Allosaurus may have hunted in packs, it has been argued that Allosaurus and other theropods had largely aggressive interactions instead of cooperative interactions with other members of their own species. The study in question noted that cooperative hunting of prey much larger than an individual predator, as is commonly inferred for theropod dinosaurs, is rare among vertebrates in general, and modern diapsid carnivores (including lizards, crocodiles, and birds) rarely cooperate to hunt in such a way. Instead, they are typically territorial and will kill and cannibalize intruders of the same species, and will also do the same to smaller individuals that attempt to eat before they do when aggregated at feeding sites. According to this interpretation, the accumulation of remains of multiple Allosaurus individuals at the same site; e.g., in the Cleveland–Lloyd Quarry, are not due to pack hunting, but to the fact that Allosaurus individuals were drawn together to feed on other disabled or dead allosaurs, and were sometimes killed in the process. This could explain the high proportion of juvenile and subadult allosaurs present, as juveniles and subadults are disproportionally killed at modern group feeding sites of animals like crocodiles and Komodo dragons. The same interpretation applies to Bakker's lair sites. There is some evidence for cannibalism in Allosaurus, including Allosaurus shed teeth found among rib fragments, possible tooth marks on a shoulder blade, and cannibalized allosaur skeletons among the bones at Bakker's lair sites.
Brain and senses
The brain of Allosaurus, as interpreted from spiral CT scanning of an endocast, was more consistent with crocodilian brains than those of the other living archosaurs, birds. The structure of the vestibular apparatus indicates that the skull was held nearly horizontal, as opposed to strongly tipped up or down. The structure of the inner ear was like that of a crocodilian, indicating that Allosaurus was more adapted to hear lower frequencies and would have had difficulty hearing subtle sounds. The olfactory bulbs were large and well suited for detecting odors, but were typical for an animal of its size.
Paleopathology | Allosaurus | Wikipedia | 458 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by the behavior of the animal than other kinds of injury. Stress fractures and tendon avulsions occurring in the forelimb have special behavioral significance since while injuries to the feet could be caused by running or migration, resistant prey items are the most probable source of injuries to the hand. Allosaurus was one of only two theropods examined in the study to exhibit a tendon avulsion, and in both cases the avulsion occurred on the forelimb. When the researchers looked for stress fractures, they found that Allosaurus had a significantly greater number of stress fractures than Albertosaurus, Ornithomimus or Archaeornithomimus. Of the 47 hand bones the researchers studied, three were found to contain stress fractures. Of the feet, 281 bones were studied and 17 were found to have stress fractures. The stress fractures in the foot bones "were distributed to the proximal phalanges" and occurred across all three weight-bearing toes in "statistically indistinguishable" numbers. Since the lower end of the third metatarsal would have contacted the ground first while an allosaur was running, it would have borne the most stress. If the allosaurs' stress fractures were caused by damage accumulating while walking or running this bone should have experience more stress fractures than the others. The lack of such a bias in the examined Allosaurus fossils indicates an origin for the stress fractures from a source other than running. The authors conclude that these fractures occurred during interaction with prey, like an allosaur trying to hold struggling prey with its feet. The abundance of stress fractures and avulsion injuries in Allosaurus provide evidence for "very active" predation-based rather than scavenging diets. | Allosaurus | Wikipedia | 406 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The left scapula and fibula of an Allosaurus fragilis specimen cataloged as USNM 4734 are both pathological, both probably due to healed fractures. The specimen USNM 8367 preserved several pathological gastralia which preserve evidence of healed fractures near their middle. Some of the fractures were poorly healed and "formed pseudoarthroses". A specimen with a fractured rib was recovered from the Cleveland-Lloyd Quarry. Another specimen had fractured ribs and fused vertebrae near the end of the tail. An apparent subadult male Allosaurus fragilis was reported to have extensive pathologies, with a total of fourteen separate injuries. The specimen MOR 693 had pathologies on five ribs, the sixth neck vertebra, the third, eighth, and thirteenth back vertebrae, the second tail vertebra and its chevron, the gastralia right scapula, manual phalanx I left ilium metatarsals III and V, the first phalanx of the third toe and the third phalanx of the second. The ilium had "a large hole...caused by a blow from above". The near end of the first phalanx of the third toe was afflicted by an involucrum.
Additionally, a subadult Allosaurus individual that suffered from spondyloarthropathy has been discovered in Dana Quarry in Wyoming. This finding represents the first known fossil evidence of spondyloarthropathy occurring in a theropod. | Allosaurus | Wikipedia | 313 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Other pathologies reported in Allosaurus include:
Willow breaks in two ribs
Healed fractures in the humerus and radius
Distortion of joint surfaces in the foot, possibly due to osteoarthritis or developmental issues
Osteopetrosis along the endosteal surface of a tibia.
Distortions of the joint surfaces of the tail vertebrae, possibly due to osteoarthritis or developmental issues
"[E]xtensive 'neoplastic' ankylosis of caudals", possibly due to physical trauma, as well as the fusion of chevrons to centra
Coossification of vertebral centra near the end of the tail
Amputation of a chevron and foot bone, both possibly a result of bites
"[E]xtensive exostoses" in the first phalanx of the third toe
Lesions similar to those caused by osteomyelitis in two scapulae
Bone spurs in a premaxilla, ungual, and two metacarpals
Exostosis in a pedal phalanx possibly attributable to an infectious disease
A metacarpal with a round depressed fracture
Paleoecology
Allosaurus was the most common large theropod in the vast tract of Western American fossil-bearing rock known as the Morrison Formation, accounting for 70 to 75% of theropod specimens, and as such was at the top trophic level of the Morrison food chain. The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains. Vegetation varied from river-lining forests of conifers, tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum. | Allosaurus | Wikipedia | 363 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Morrison Formation has been a rich fossil hunting ground. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Animal fossils discovered include bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, several species of pterosaur, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Dinosaurs known from the Morrison include the theropods Ceratosaurus, Ornitholestes, Tanycolagreus, and Torvosaurus, the sauropods Haplocanthosaurus, Camarasaurus, Cathetosaurus, Brachiosaurus, Suuwassea, Apatosaurus, Brontosaurus, Barosaurus, Diplodocus, Supersaurus, Amphicoelias, and Maraapunisaurus, and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Allosaurus is commonly found at the same sites as Apatosaurus, Camarasaurus, Diplodocus, and Stegosaurus. The Late Jurassic formations of Portugal where Allosaurus is present are interpreted as having been similar to the Morrison, but with a stronger marine influence. Many of the dinosaurs of the Morrison Formation are the same genera as those seen in Portuguese rocks (mainly Allosaurus, Ceratosaurus, Torvosaurus, and Stegosaurus), or have a close counterpart (Brachiosaurus and Lusotitan, Camptosaurus and Draconyx). | Allosaurus | Wikipedia | 358 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal. The three appear to have had different ecological niches, based on anatomy and the location of fossils. Ceratosaurus and Torvosaurus may have preferred to be active around waterways, and had lower, thinner bodies that would have given them an advantage in forest and underbrush terrains, whereas Allosaurus was more compact, with longer legs, faster but less maneuverable, and seems to have preferred dry floodplains. Ceratosaurus, better known than Torvosaurus, differed noticeably from Allosaurus in functional anatomy by having a taller, narrower skull with large, broad teeth. Allosaurus was itself a potential food item to other carnivores, as illustrated by an Allosaurus pubic foot marked by the teeth of another theropod, probably Ceratosaurus or Torvosaurus. The location of the bone in the body (along the bottom margin of the torso and partially shielded by the legs), and the fact that it was among the most massive in the skeleton, indicates that the Allosaurus was being scavenged.
A bone assemblage in the Upper Jurassic Mygatt-Moore Quarry preserves an unusually high occurrence of theropod bite marks, most of which can be attributed to Allosaurus and Ceratosaurus, while others could have been made by Torvosaurus given the size of the striations. While the position of the bite marks on the herbivorous dinosaurs is consistent with predation or early access to remains, bite marks found on Allosaurus material suggest scavenging, either from the other theropods or from another Allosaurus. The unusually high concentration of theropod bite marks compared to other assemblages could be explained either by a more complete utilization of resources during a dry season by theropods, or by a collecting bias in other localities. | Allosaurus | Wikipedia | 390 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The AK-47, officially known as the Avtomat Kalashnikova (; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kalashnikov, it is the originating firearm of the Kalashnikov (or "AK") family of rifles. After more than seven decades since its creation, the AK-47 model and its variants remain one of the most popular and widely used firearms in the world.
Design work on the AK-47 began in 1945. It was presented for official military trials in 1947, and, in 1948, the fixed-stock version was introduced into active service for selected units of the Soviet Army. In early 1949, the AK was officially accepted by the Soviet Armed Forces and used by the majority of the member states of the Warsaw Pact.
The model and its variants owe their global popularity to their reliability under harsh conditions, low production cost (compared to contemporary weapons), availability in virtually every geographic region, and ease of use. The AK has been manufactured in many countries and has seen service with armed forces as well as irregular forces and insurgencies throughout the world. , "of the estimated 500 million firearms worldwide, approximately 100 million belong to the Kalashnikov family, three-quarters of which are AK-47s". The model is the basis for the development of many other types of individual, crew-served, and specialized firearms.
History
Origins
During World War II, the Sturmgewehr 44 rifle used by German forces made a deep impression on their Soviet counterparts. The select-fire rifle was chambered for a new intermediate cartridge, the 7.92×33mm Kurz, and combined the firepower of a submachine gun with the range and accuracy of a rifle. On 15 July 1943, an earlier model of the Sturmgewehr was demonstrated before the People's Commissariat of Arms of the USSR. The Soviets were impressed with the weapon and immediately set about developing an intermediate caliber fully automatic rifle of their own, to replace the PPSh-41 submachine guns and outdated Mosin–Nagant bolt-action rifles that armed most of the Soviet Army. | AK-47 | Wikipedia | 463 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Soviets soon developed the 7.62×39mm M43 cartridge, used in the semi-automatic SKS carbine and the RPD light machine gun. Shortly after World War II, the Soviets developed the AK-47 rifle, which quickly replaced the SKS in Soviet service. Introduced in 1959, the AKM is a lighter stamped steel version and the most ubiquitous variant of the entire AK series of firearms. In the 1960s, the Soviets introduced the RPK light machine gun, an AK-type weapon with a stronger receiver, a longer heavy barrel, and a bipod, that eventually replaced the RPD light machine gun.
Concept
Mikhail Kalashnikov began his career as a weapon designer in 1941 while recuperating from a shoulder wound that he received during the Battle of Bryansk. Kalashnikov himself stated..."I was in the hospital, and a soldier in the bed beside me asked: 'Why do our soldiers have only one rifle for two or three of our men when the Germans have automatics?' So I designed one. I was a soldier, and I created a machine gun for a soldier. It was called an Avtomat Kalashnikova, the automatic weapon of Kalashnikov—AK—and it carried the year of its first manufacture, 1947."
The AK-47 is best described as a hybrid of previous rifle technology innovations. "Kalashnikov decided to design an automatic rifle combining the best features of the American M1 Garand and the German StG 44." Kalashnikov's team had access to these weapons and did not need to "reinvent the wheel". Kalashnikov himself observed: "A lot of Russian Army soldiers ask me how one can become a constructor, and how new weaponry is designed. These are very difficult questions. Each designer seems to have his own paths, his own successes and failures. But one thing is clear: before attempting to create something new, it is vital to have a good appreciation of everything that already exists in this field. I myself have had many experiences confirming this to be so."
Some claimed that Kalashnikov copied designs like Bulkin's TKB-415 or Simonov's AVS-31. | AK-47 | Wikipedia | 455 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Early designs
Kalashnikov started work on a submachine gun design in 1942 and a light machine gun design in 1943. Early in 1944, Kalashnikov was given some 7.62×39mm M43 cartridges and informed that other designers were working on weapons for this new Soviet small-arms cartridge. It was suggested that a new weapon might well lead to greater things. He then undertook work on the new rifle. In 1944, he entered a design competition with this new 7.62×39mm, semi-automatic, gas-operated, long-stroke piston carbine, strongly influenced by the American M1 Garand. The new rifle was in the same class as the SKS-45 carbine, with a fixed magazine and gas tube above the barrel. However, the new Kalashnikov design lost out to a Simonov design.
In 1946, a new design competition was initiated to develop a new rifle. Kalashnikov submitted a gas-operated rifle with a short-stroke gas piston above the barrel, a breechblock mechanism similar to his 1944 carbine, and a curved 30-round magazine. Kalashnikov's rifles, the AK-1 (with a milled receiver) and AK-2 (with a stamped receiver) proved to be reliable weapons and were accepted to a second round of competition along with other designs.
These prototypes (also known as the AK-46) had a rotary bolt, a two-part receiver with separate trigger unit housing, dual controls (separate safety and fire selector switches), and a non-reciprocating charging handle located on the left side of the weapon. This design had many similarities to the StG 44. In late 1946, as the rifles were being tested, one of Kalashnikov's assistants, Aleksandr Zaitsev, suggested a major redesign to improve reliability. At first, Kalashnikov was reluctant, given that their rifle had already fared better than its competitors. Eventually, however, Zaitsev managed to persuade Kalashnikov. | AK-47 | Wikipedia | 410 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
In November 1947, the new prototypes (AK-47s) were completed. The rifle used a long-stroke gas piston above the barrel. The upper and lower receivers were combined into a single receiver. The selector and safety were combined into a single control lever/dust cover on the right side of the rifle and the bolt handle was attached to the bolt carrier. This simplified the design and production of the rifle. The first army trial series began in early 1948. The new rifle proved to be reliable under a wide range of conditions and possessed convenient handling characteristics. In 1949, it was adopted by the Soviet Army as the "7.62 mm Kalashnikov rifle (AK)".
Further development
There were many difficulties during the initial phase of production. The first production models had stamped sheet metal receivers with a milled trunnion and butt stock insert and a stamped body. Difficulties were encountered in welding the guide and ejector rails, causing high rejection rates. Instead of halting production, a heavy machined receiver was substituted for the sheet metal receiver. Even though production of these milled rifles started in 1951, they were officially referred to as AK-49, based on the date their development started, but they are widely known in the collectors' and current commercial market as "Type 2 AK-47". This was a more costly process, but the use of machined receivers accelerated production as tooling and labor for the earlier Mosin–Nagant rifle's machined receiver were easily adapted. Partly because of these problems, the Soviets were not able to distribute large numbers of the new rifles to soldiers until 1956. During this time, production of the interim SKS rifle continued.
Once the manufacturing difficulties of non-milled receivers had been overcome, a redesigned version designated the AKM (M for "modernized" or "upgraded"; in Russian: []) was introduced in 1959. This new model used a stamped sheet metal receiver and featured a slanted muzzle brake on the end of the barrel to compensate for muzzle rise under recoil. In addition, a hammer retarder was added to prevent the weapon from firing out of battery (without the bolt being fully closed), during rapid or fully automatic fire. This is also sometimes referred to as a "cyclic rate reducer", or simply "rate reducer", as it also has the effect of reducing the number of rounds fired per minute during fully automatic fire. The rifle was also roughly one-third lighter than the previous model. | AK-47 | Wikipedia | 507 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Most licensed and unlicensed productions of the Kalashnikov assault rifle abroad were of the AKM variant, partially due to the much easier production of the stamped receiver. This model is the most commonly encountered, having been produced in much greater quantities. All rifles based on the Kalashnikov design are often colloquially referred to as "AK-47s" in the West and some parts of Asia, although this is only correct when applied to rifles based on the original three receiver types. In most former Eastern Bloc countries, the weapon is known simply as the "Kalashnikov" or "AK". The differences between the milled and stamped receivers includes the use of rivets rather than welds on the stamped receiver, as well as the placement of a small dimple above the magazine well for stabilization of the magazine.
Replacement
In 1974, the Soviets began replacing their AK-47 and AKM rifles with a newer design, the AK-74, which uses 5.45×39mm ammunition. This new rifle and cartridge had only started to be manufactured in Eastern European nations when the Soviet Union collapsed, drastically slowing the production of the AK-74 and other weapons of the former Soviet bloc.
Design
The AK-47 was designed to be a simple, reliable fully automatic rifle that could be manufactured quickly and cheaply, using mass production methods that were state of the art in the Soviet Union during the late 1940s. The AK-47 uses a long-stroke gas system generally associated with high reliability in adverse conditions. The large gas piston, generous clearance between moving parts, and tapered cartridge case design allow the gun to endure large amounts of foreign matter and fouling without failing to cycle.
Cartridge | AK-47 | Wikipedia | 342 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK fires the 7.62×39mm cartridge with a muzzle velocity of .
The cartridge weight is , and the projectile weight is . The original Soviet M43 bullets are 123-grain boat-tail bullets with a copper-plated steel jacket, a large steel core, and some lead between the core and the jacket. The AK has excellent penetration when shooting through heavy foliage, walls, or a common vehicle's metal body and into an opponent attempting to use these things as cover. The 7.62×39mm M43 projectile does not generally fragment when striking an opponent and has an unusual tendency to remain intact even after making contact with bone. The 7.62×39mm round produces significant wounding in cases where the bullet tumbles (yaws) in tissue, but produces relatively minor wounds in cases where the bullet exits before beginning to yaw. In the absence of yaw, the M43 round can pencil through tissue with relatively little injury.
Most, if not all, of the 7.62×39mm ammunition found today is of the upgraded M67 variety. This variety deleted the steel insert, shifting the center of gravity rearward, and allowing the projectile to destabilize (or yaw) at about , nearly earlier in tissue than the M43 round. This change also reduces penetration in ballistic gelatin to ~ for the newer M67 round versus ~ for the older M43 round. However, the wounding potential of M67 is mostly limited to the small permanent wound channel the bullet itself makes, especially when the bullet yaws.
Operating mechanism | AK-47 | Wikipedia | 321 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
To fire, the operator inserts a loaded magazine, pulls back and releases the charging handle, and then pulls the trigger. In semi-automatic, the firearm fires only once, requiring the trigger to be released and depressed again for the next shot. In fully automatic, the rifle continues to fire automatically cycling fresh rounds into the chamber until the magazine is exhausted or pressure is released from the trigger. After ignition of the cartridge primer and propellant, rapidly expanding propellant gases are diverted into the gas cylinder above the barrel through a vent near the muzzle. The build-up of gases inside the gas cylinder drives the long-stroke piston and bolt carrier rearward and a cam guide machined into the underside of the bolt carrier, along with an ejector spur on the bolt carrier rail guide, rotates the bolt approximately 35° and unlocks it from the barrel extension via a camming pin on the bolt. The moving assembly has about of free travel, which creates a delay between the initial recoil impulse of the piston and the bolt unlocking sequence, allowing gas pressures to drop to a safe level before the seal between the chamber and the bolt is broken. The AK-47 does not have a gas valve; excess gases are ventilated through a series of radial ports in the gas cylinder. Unlike many other rifle platforms, such as the AR-15 platform, the Kalashnikov platform bolt locking lugs are chamfered allowing for primary extraction upon bolt rotation which aids reliable feeding and extraction, albeit not with that much force due to the short distance the bolt carrier travels before acting on the locking lug. The Kalashnikov platform then uses an extractor claw along with a fin shaped ejector to eject the spent cartridge case.
Barrel
The rifle received a barrel with a chrome-lined bore and four right-hand grooves at a 240 mm (1 in 9.45 in) or 31.5 calibers rifling twist rate. The gas block contains a gas channel that is installed at a slanted angle with the bore axis. The muzzle is threaded for the installation of various muzzle devices such as a muzzle brake or a blank-firing adaptor.
Gas block
The gas block of the AK-47 features a cleaning rod capture or sling loop. Gas relief ports that alleviate gas pressure are placed horizontally in a row on the gas cylinder.
Fire selector | AK-47 | Wikipedia | 478 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The fire selector is a large lever located on the right side of the rifle; it acts as a dust cover and prevents the charging handle from being pulled fully to the rear when it is on safe. It is operated by the shooter's right fore-fingers and has three settings: safe (up), full-auto (center), and semi-auto (down). The reason for this is that a soldier under stress will push the selector lever down with considerable force, bypassing the full-auto stage and setting the rifle to semi-auto. To set the AK-47 to full-auto requires the deliberate action of centering the selector lever. To operate the fire selector lever, right-handed shooters have to briefly remove their right hand from the pistol grip, which is ergonomically sub-optimal. Some AK-type rifles also have a more traditional selector lever on the left side of the receiver, just above the pistol grip. This lever is operated by the shooter's right thumb and has three settings: safe (forward), full-auto (center), and semi-auto (backward).
Sights
The AK-47 uses a notched rear tangent iron sight calibrated in increments from . The front sight is a post adjustable for elevation in the field. Horizontal adjustment requires a special drift tool and is done by the armory before the issue or if the need arises by an armorer after the issue. The sight line elements are approximately over the bore axis. The "point-blank range" battle zero setting "П" standing for постоянная (constant) on the 7.62×39mm AK-47 rear tangent sight element corresponds to a zero. These settings mirror the Mosin–Nagant and SKS rifles, which the AK-47 replaced. For the AK-47 combined with service cartridges, the 300 m battle zero setting limits the apparent "bullet rise" within approximately relative to the line of sight. Soldiers are instructed to fire at any target within this range by simply placing the sights on the center of mass (the belt buckle, according to Russian and former Soviet doctrine) of the enemy target. Any errors in range estimation are tactically irrelevant, as a well-aimed shot will hit the torso of the enemy soldier. Some AK-type rifles have a front sight with a flip-up luminous dot that is calibrated at , for improved night fighting. | AK-47 | Wikipedia | 496 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Furniture
The AK-47 was originally equipped with a buttstock, handguard, and an upper heat guard made from solid wood. With the introduction of the Type 3 receiver the buttstock, lower handguard, and upper heat guard were manufactured from birch plywood laminates. Such engineered woods are stronger and resist warping better than the conventional one-piece patterns, do not require lengthy maturing, and are cheaper. The wooden furniture was finished with the Russian amber shellac finishing process. AKS and AKMS models featured a downward-folding metal butt-stock similar to that of the German MP40 submachine-gun, for use in the restricted space in the BMP infantry combat vehicle, as well as by paratroops. All 100 series AKs use plastic furniture with side-folding stocks.
Magazines
The standard magazine capacity is 30 rounds. There are also 10-, 20-, and 40-round box magazines, as well as 75-round drum magazines.
The AK-47's standard 30-round magazines have a pronounced curve that allows them to smoothly feed ammunition into the chamber. Their heavy steel construction combined with "feed-lips" (the surfaces at the top of the magazine that control the angle at which the cartridge enters the chamber) machined from a single steel billet makes them highly resistant to damage. These magazines are so strong that "Soldiers have been known to use their mags as hammers, and even bottle openers". This contributes to the AK-47 magazine being more reliable but makes it heavier than U.S. and NATO magazines. | AK-47 | Wikipedia | 321 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The early slab-sided steel AK-47 30-round detachable box magazines had sheet-metal bodies and weighed empty. The later steel AKM 30-round magazines had lighter sheet-metal bodies with prominent reinforcing ribs weighing empty. To further reduce weight, a lightweight magazine with an aluminum body with a prominent reinforcing waffle rib pattern weighing empty was developed for the AKM that proved to be too fragile, and the small issued amount of these magazines were quickly withdrawn from service. As a replacement steel-reinforced 30-round plastic 7.62×39mm box magazines were introduced. These rust-colored magazines weigh empty and are often mistakenly identified as being made of Bakelite (a phenolic resin), but were fabricated from two parts of AG-S4 molding compound (a glass-reinforced phenol-formaldehyde binder impregnated composite), assembled using an epoxy resin adhesive. Noted for their durability, these magazines did however compromise the rifle's camouflage and lacked the small horizontal reinforcing ribs running down both sides of the magazine body near the front that were added on all later plastic magazine generations. A second-generation steel-reinforced dark-brown (color shades vary from maroon to plum to near black) 30-round 7.62×39mm magazine was introduced in the early 1980s, fabricated from ABS plastic. The third generation steel-reinforced 30-round 7.62×39mm magazine is similar to the second generation, but is darker colored and has a matte non-reflective surface finish. The current issue is a steel-reinforced matte true black non- reflective surface finished 7.62×39mm 30-round magazine, fabricated from ABS plastic weighing empty.
Early steel AK-47 magazines are long; the later ribbed steel AKM and newer plastic 7.62×39mm magazines are about shorter.
The transition from steel to mainly plastic magazines yields a significant weight reduction and allows a soldier to carry more ammunition for the same weight.
All 7.62×39mm AK magazines are backward compatible with older AK variants.
10.12 kg (22.3 lb) is the maximum amount of ammo that the average soldier can comfortably carry. It also allows for the best comparison of the three most common 7.62×39mm AK magazines. | AK-47 | Wikipedia | 477 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Most Yugoslavian and some East German AK magazines were made with cartridge followers that hold the bolt open when empty; however, most AK magazine followers allow the bolt to close when the magazine is empty.
Accessories
Accessories supplied with the rifle include a long 6H3 bayonet featuring a long spear point blade. The AK-47 bayonet is installed by slipping the diameter muzzle ring around the muzzle and latching the handle down on the bayonet lug under the front sight base.
All current model AKM rifles can mount under-barrel 40 mm grenade launchers such as the GP-25 and its variants, which can fire up to 20 rounds per minute and have an effective range of up to 400 meters. The main grenade is the VOG-25 (VOG-25M) fragmentation grenade which has a 6 m (9 m) (20 ft (30 ft)) lethality radius. The VOG-25P/VOG-25PM ("jumping") variant explodes above the ground.
The AK-47 can also mount a (rarely used) cup-type grenade launcher, the Kalashnikov grenade launcher that fires standard RGD-5 Soviet hand grenades. The maximum effective range is approximately 150 meters. This launcher can also be used to launch tear gas and riot control grenades.
All current AKs (100 series) and some older models have side rails for mounting a variety of scopes and sighting devices, such as the PSO-1 Optical Sniper Sight. The side rails allow for the removal and remounting of optical accessories without interfering with the zeroing of the optic. However, the 100 series side folding stocks cannot be folded with the optics mounted.
Characteristics
Service life
The AK-47 and its variants have been and are made in dozens of countries, with "quality ranging from finely engineered weapons to pieces of questionable workmanship." As a result, the AK-47 has a service/system life of approximately 6,000, to 10,000, to 15,000 rounds. The AK-47 was designed to be a cheap, simple, easy-to-manufacture rifle, perfectly matching Soviet military doctrine that treats equipment and weapons as disposable items. As units are often deployed without adequate logistical support and dependent on "battlefield cannibalization" for resupply, it is more cost-effective to replace rather than repair weapons. | AK-47 | Wikipedia | 484 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 has small parts and springs that need to be replaced every few thousand rounds. However, "Every time it is disassembled beyond the field stripping stage, it will take some time for some parts to regain their fit, and some parts may tend to shake loose and fall out when firing the weapon. Some parts of the AK-47 line are riveted together. Repairing these can be quite a hassle since the end of the rivet has to be ground off and a new one set after the part is replaced."
Variants
Early variants (7.62×39mm)
Issue of 1948/49: Type 1: The very earliest models, stamped sheet metal receivers, are now very rare.
Issue of 1951: Type 2: Has a milled receiver. The barrel and chamber are chrome-plated to resist corrosion.
Issue of 1954/55: Type 3: Lightened, milled receiver variant. Rifle weight is .
AKS (AKS-47): Type 1, 2, or 3 receivers: Featured a downward under folding metal stock similar to that of the MP 40, for use in the restricted space of the BMP infantry combat vehicle, as well as for airborne troops.
AKN (AKSN): Night sight rail.
Modernized (7.62×39mm)
AKM: A simplified, lighter version of the AK-47; the Type 4 receiver is made from stamped and riveted sheet metal. A slanted muzzle device was added to reduce muzzle rise in automatic fire. The rifle weight is due to the lighter receiver. This is the most ubiquitous variant of the AK-47.
AKMS: Under-folding stock version of the AKM intended for airborne troops.
AKMN (AKMSN): Night scope rail.
AKML (AKMSL): Slotted flash suppressor and night scope rail.
RPK: Hand-held machine gun version with longer barrel and bipod. The variants—RPKS, RPKN (RPKSN), RPKL (RPKSL)—mirror AKM variants. The "S" variants have a side-folding wooden stock.
Foreign Variants (7.62×39mm)
Type 56: Chinese assault rifle based on the . Still in production primarily for export markets.
For the further developed AK models, see Kalashnikov rifles.
Production
Manufacturing countries of AK-47 and its variants in alphabetical order. | AK-47 | Wikipedia | 502 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
A private company Kalashnikov Concern (formerly Izhmash) from Russia has repeatedly claimed that the majority of foreign manufacturers are producing AK-type rifles without proper licensing.
Accuracy potential
US military method
The AK-47's accuracy is generally sufficient to hit an adult male torso out to about , though even experts firing from prone or bench rest positions at this range were observed to have difficulty placing ten consecutive rounds on target. Later designs did not significantly improve the rifle's accuracy. An AK can fire a 10-shot group of at , and at The newer stamped-steel receiver AKM models, while more rugged and less prone to metal fatigue, are less accurate than the forged/milled receivers of their predecessors: the milled AK-47s are capable of shooting groups at , whereas the stamped AKMs are capable of shooting groups at .
The best shooters can hit a man-sized target at within five shots (firing from a prone or bench rest position) or ten shots (standing).
The single-shot hit-probability on the NATO E-type Silhouette Target (a human upper body half and head silhouette) of the AK-47 and the later developed AK-74, M16A1, and M16A2 rifles were measured by the US military under ideal proving ground conditions in the 1980s as follows:
Under worst field exercise circumstances, the hit probabilities for all the tested rifles were drastically reduced, from 34% at 50m down to 3–4% at 600m with no significant differences between weapons at each range.
Russian method
The following table represents the Russian circular error probable method for determining accuracy, which involves drawing two circles on the target, one for the maximum vertical dispersion of hits and one for the maximum horizontal dispersion of hits. They then disregard the hits on the outer part of the target and only count half of the hits (50% or R50) on the inner part of the circles. This significantly reduces the overall diameter of the groups. They then use both the vertical and horizontal measurements of the reduced groups to measure accuracy. When the R50 results are doubled, the hit probability increases to 93.7%.
R50 means the closest 50 percent of the shot group will all be within a circle of the mentioned diameter.
The vertical and horizontal mean (R50) deviations with service ammunition at for AK platforms are.
Users
Current | AK-47 | Wikipedia | 482 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
− Type 56 variant.
− EKAM: The counter-terrorist unit of the Hellenic Police
− Type 58 variant
– Locally made as well as being in service with the Army
− Used by Thahan Phran
Non-state current
ELN
FARC dissidents
− Captured from the Syrian Army
Karen National Defence Organisation
Karen National Liberation Army
Kurdistan Workers Party
National Movement for the Liberation of Azawad
New People's Army
Syrian opposition
Ta'ang National Liberation Army
Former
− MPi-K (AK-47) and MPi-KM (AKM)
− Passed on to the unified Vietnamese state
− Used by the Panama Defense Forces
− Replaced by the AKM and AK-74
− Captured rifles were issued to ARVN irregular units
Non-state former
Afghan mujahideen − CIA supplied Egyptian and Chinese variants
Contras
Farabundo Martí National Liberation Front
Iraqi insurgents
Khmer Rouge
Liberation Tigers of Tamil Eelam
Malayan National Liberation Army
Moro National Liberation Front
Northern Alliance
Provisional Irish Republican Army − Supplied by Libya
RENAMO
Revolutionary Armed Forces of Colombia
Viet Cong
Vigorous Burmese Student Warriors
Illicit trade
Throughout the world, the AK and its variants are commonly used by governments, revolutionaries, terrorists, criminals, and civilians alike. In some countries, such as Somalia, Rwanda, Mozambique, Congo, and Tanzania, the prices for Black Market AKs are between $30 and $125 per weapon and prices have fallen in the last few decades due to mass counterfeiting. In Kenya, "an AK-47 fetches five head of cattle (about 10,000 Kenya shillings or 100 U.S. dollars) when offered for barter, but costs almost half that price when cash is paid". There are places around the world where AK-type weapons can be purchased on the black market "for as little as $6, or traded for a chicken or a sack of grain".
The AK-47 has also spawned a cottage industry of sorts and has been copied and manufactured (one gun at a time) in small shops around the world (see Khyber Pass Copy). The estimated numbers of AK-type weapons vary greatly. The Small Arms Survey suggests that "between 70 and 100 million of these weapons have been produced since 1947". The World Bank estimates that out of the 500 million total firearms available worldwide, 100 million are of the Kalashnikov family, and 75 million are AK-47s. Because AK-type weapons have been made in many countries, often illicitly, it is impossible to know how many exist.
Conflicts | AK-47 | Wikipedia | 508 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 has been used in the following conflicts:
1940s
Malayan Emergency (1948−1960)
1950s
Hungarian Revolution (1956)
Vietnam War (1955–1975)
Laotian Civil War (1959–1975)
1960s
Congo Crisis (1960–1965)
Portuguese Colonial War (1961–1974)
Rhodesian Bush War (1964–1979)
The Troubles (late 1960s–1998)
Communist insurgency in Thailand (1965–1983)
South African Border War (1966–1990)
India-China clashes (1967)
Cambodian Civil War (1968–1975)
Communist insurgency in Malaysia (1968–1989)
Moro Conflict (1968−2019)
1970s
Yom Kippur War (1973)
Ethiopian Civil War (1974–1991)
Western Sahara War (1975–1991)
Cambodian–Vietnamese War (1978–1989)
Chadian–Libyan War (1978–1987)
Soviet–Afghan War (1979–1989)
1980s
1979 Kurdish rebellion in Iran
Iran–Iraq War (1980–1988)
Insurgency in Jammu and Kashmir (1988–present)
Sri Lankan Civil War (1983–2009)
United States invasion of Grenada (1983)
South Lebanon conflict (1985–2000)
Lord's Resistance Army insurgency (1987–present)
United States invasion of Panama (1989)
1990s
KDPI insurgency (1989–1996)
Tuareg rebellion (1990–1995)
Gulf War (1990–1991)
Somali Civil War (1991–present)
Yugoslav Wars (1991–2001)
Burundian Civil War (1993–2005)
First Chechen War (1994−1996)
Republic of the Congo Civil War (1997–1999)
Kargil War (1999)
2000s
War in Afghanistan (2001–2021)
Iraq War (2003–2011)
South Thailand insurgency (2004–present)
Mexican drug war (2006–present)
2010s
Libyan Civil War (2011)
Syrian civil war (2011–present)
Iraqi insurgency (2011–2013)
Central African Republic Civil War (2012–present)
Mali War (2012–present)
Russo-Ukrainian War (2014–present)
Western Iran clashes (2016–present)
2020s
Second Nagorno-Karabakh War (2020)
Tigray War (2020–2022)
Myanmar civil war (2021–present)
Russian invasion of Ukraine (2022–present)
September–October 2022 attacks on Iraqi Kurdistan
Israel-Hamas War (2023–present)
Cultural influence and impact | AK-47 | Wikipedia | 483 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
During the Cold War, the Soviet Union and the People's Republic of China, as well as United States and other NATO nations supplied arms and technical knowledge to numerous countries and rebel forces around the world. During this time the Western countries used relatively expensive automatic rifles, such as the FN FAL, the HK G3, the M14, and the M16. In contrast, the Russians and Chinese used the AK-47; its low production cost and ease of manufacture allow them to make AKs in vast numbers.
In the pro-communist states, the AK-47 became a symbol of the Third World revolution. They were utilized in the Cambodian Civil War and the Cambodian–Vietnamese War. During the 1980s, the Soviet Union became the principal arms dealer to countries embargoed by Western nations, including Middle Eastern nations such as Libya and Syria, which welcomed Soviet Union backing against Israel. After the fall of the Soviet Union, AK-47s were sold both openly and on the black market to any group with cash, including drug cartels and dictatorial states, and more recently they have been seen in the hands of Islamic groups such as Al-Qaeda, ISIL, and the Taliban in Afghanistan and Iraq, and FARC, Ejército de Liberación Nacional guerrillas in Colombia.
In Russia, the Kalashnikov is a tremendous source of national pride. "The family of the inventor of the world's most famous rifle, Mikhail Kalashnikov, has authorized German engineering company MMI to use the well-known Kalashnikov name on a variety of not-so-deadly goods." In recent years, Kalashnikov Vodka has been marketed with souvenir bottles in the shape of the AK-47 Kalashnikov. There are also Kalashnikov watches, umbrellas, and knives. | AK-47 | Wikipedia | 369 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Kalashnikov Museum (also called the AK-47 museum) opened on 4 November 2004 in Izhevsk, Udmurt Republic. This city is in the Ural Region of Russia. The museum chronicles the biography of General Kalashnikov and documents the invention of the AK-47. The museum complex of Kalashnikov's small arms, a series of halls, and multimedia exhibitions are devoted to the evolution of the AK-47 rifle and attracts 10,000 monthly visitors. Nadezhda Vechtomova, the museum director, stated in an interview that the purpose of the museum is to honor the ingenuity of the inventor and the hard work of the employees and to "separate the weapon as a weapon of murder from the people who are producing it and to tell its history in our country".
On 19 September 2017 a monument of Kalashnikov was unveiled in central Moscow. A protester, later detained by police, attempted to unfurl a banner reading "a creator of weapons is a creator of death".
The proliferation of this weapon is reflected by more than just numbers. The AK-47 is included on the flag of Mozambique and its emblem, an acknowledgment that the country gained its independence in large part through the effective use of their AK-47s. It is also found in the coats of arms of East Timor, Zimbabwe and the revolution era Burkina Faso, as well as in the flags of Hezbollah, Syrian Resistance, FARC-EP, the New People's Army, TKP/TIKKO and the International Revolutionary People's Guerrilla Forces.
U.S. and Western Europe countries frequently associate the AK-47 with their enemies; both Cold War era and present-day. For example, Western works of fiction (movies, television, novels, video games) often portray criminals, gang members, insurgents, and terrorists using AK-47s as the weapon of choice. Conversely, throughout the developing world, the AK-47 can be positively attributed with revolutionaries against foreign occupation, imperialism, or colonialism.
In Ireland the AK-47 is associated with The Troubles due to its extensive use by republican paramilitaries during this period. In 2013, a decommissioned AK-47 was included in the A History of Ireland in 100 Objects collection. | AK-47 | Wikipedia | 469 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 made an appearance in U.S. popular culture as a recurring focus in the Nicolas Cage film Lord of War (2005). Numerous monologues in the movie focus on the weapon, and its effects on global conflict and the gun running market.
In Iraq and Afghanistan, private military company contractors from the U.K. and other countries used the AK-47 and its variants along with Western firearms such as the AR-15.
In 2006, the Colombian musician and peace activist César López devised the escopetarra, an AK converted into a guitar. One sold for US$17,000 in a fundraiser held to benefit the victims of anti-personnel mines, while another was exhibited at the United Nations' Conference on Disarmament.
In Mexico, the AK-47 is known as "Cuerno de Chivo" (literally "Goat's Horn") because of its curved magazine design. It is one of the weapons of choice of Mexican drug cartels. It is sometimes mentioned in Mexican folk music lyrics.
Gallery | AK-47 | Wikipedia | 211 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. The device was limited by the technology of the day. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the first electronic ALU (arithmetic logic unit) which is integrated into every modern processor's design.
Its unique contribution was to make computing faster by being the first to use vacuum tubes to do arithmetic calculations. Prior to this, slower electro-mechanical methods were used by Konrad Zuse's Z1 computer, and the simultaneously developed Harvard Mark I. The first electronic, programmable, digital machine, the Colossus computer from 1943 to 1945, used similar tube-based technology as ABC.
Overview
Conceived in 1937, the machine was built by Iowa State College mathematics and physics professor John Vincent Atanasoff with the help of graduate student Clifford Berry. It was designed only to solve systems of linear equations and was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was not perfected, and when John Vincent Atanasoff left Iowa State College for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. The computer was designated an IEEE Milestone in 1990.
Atanasoff and Berry's computer work was not widely known until it was rediscovered in the 1960s, amid patent disputes over the first instance of an electronic computer. At that time ENIAC, that had been created by John Mauchly and J. Presper Eckert, was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff. When, in the mid-1970s, the secrecy surrounding the British World War II development of the Colossus computers that pre-dated ENIAC, was lifted and Colossus was described at a conference in Los Alamos, New Mexico, in June 1976, John Mauchly and Konrad Zuse were reported to have been astonished.
Design and construction | Atanasoff–Berry computer | Wikipedia | 481 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
According to Atanasoff's account, several key principles of the Atanasoff–Berry computer were conceived in a sudden insight after a long nighttime drive to Rock Island, Illinois, during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing, regenerative capacitor memory, and a separation of memory and computing functions. The mechanical and logic design was worked out by Atanasoff over the next year. A grant application to build a proof of concept prototype was submitted in March 1939 to the Agronomy department, which was also interested in speeding up computation for economic and research analysis. $5,000 of further funding () to complete the machine came from the nonprofit Research Corporation of New York City.
The ABC was built by Atanasoff and Berry in the basement of the physics building at Iowa State College from 1939 to 1942. The initial funds were released in September, and the 11-tube prototype was first demonstrated in October 1939. A December demonstration prompted a grant for construction of the full-scale machine. The ABC was built and tested over the next two years. A January 15, 1941, story in the Des Moines Register announced the ABC as "an electrical computing machine" with more than 300 vacuum tubes that would "compute complicated algebraic equations" (but gave no precise technical description of the computer). The system weighed more than . It contained approximately of wire, 280 dual-triode vacuum tubes, 31 thyratrons, and was about the size of a desk.
It was not programmable, which distinguishes it from more general machines of the same era, such as Konrad Zuse's 1941 Z3 (or earlier iterations) and the Colossus computers of 1943–1945. Nor did it implement the stored-program architecture, first implemented in the Manchester Baby of 1948, required for fully general-purpose practical computing machines.
The machine was, however, the first to implement:
Using vacuum tubes, rather than wheels, ratchets, mechanical switches, or telephone relays, allowing for greater speed than previous computers
Using capacitors for memory, rather than mechanical components, allowing for greater speed and density | Atanasoff–Berry computer | Wikipedia | 438 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
The memory of the Atanasoff–Berry computer was a system called regenerative capacitor memory, which consisted of a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and two spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second. Data was represented as 50-bit binary fixed-point numbers. The electronics of the memory and arithmetic units could store and operate on 60 such numbers at a time (3000 bits).
The alternating current power-line frequency of 60 Hz was the primary clock rate for the lowest-level operations.
The arithmetic logic functions were fully electronic, implemented with vacuum tubes. The family of logic gates ranged from inverters to two- and three-input gates. The input and output levels and operating voltages were compatible between the different gates. Each gate consisted of one inverting vacuum-tube amplifier, preceded by a resistor divider input network that defined the logical function. The control logic functions, which only needed to operate once per drum rotation and therefore did not require electronic speed, were electromechanical, implemented with relays.
The ALU operated on only one bit of each number at a time; it kept the carry/borrow bit in a capacitor for use in the next AC cycle.
Although the Atanasoff–Berry computer was an important step up from earlier calculating machines, it was not able to run entirely automatically through an entire problem. An operator was needed to operate the control switches to set up its functions, much like the electro-mechanical calculators and unit record equipment of the time. Selection of the operation to be performed, reading, writing, converting to or from binary to decimal, or reducing a set of equations was made by front-panel switches and, in some cases, jumpers.
There were two forms of input and output: primary user input and output and an intermediate results output and input. The intermediate results storage allowed operation on problems too large to be handled entirely within the electronic memory. (The largest problem that could be solved without the use of the intermediate output and input was two simultaneous equations, a trivial problem.) | Atanasoff–Berry computer | Wikipedia | 470 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50-bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these units, primarily attributed to lack of control of the sheets' material characteristics. In retrospect, a solution could have been to add a parity bit to each number as written. This problem was not solved by the time Atanasoff left the university for war-related work.
Primary user input was decimal, via standard IBM 80-column punched cards, and output was decimal, via a front-panel display.
Function
The ABC was designed for a specific purpose the solution of systems of simultaneous linear equations. It could handle systems with up to 29 equations, a difficult problem for the time. Problems of this scale were becoming common in physics, the department in which John Atanasoff worked. The machine could be fed two linear equations with up to 29 variables and a constant term and eliminate one of the variables. This process would be repeated manually for each of the equations, which would result in a system of equations with one fewer variable. Then the whole process would be repeated to eliminate another variable.
George W. Snedecor, the head of Iowa State's Statistics Department, was very likely the first user of an electronic digital computer to solve real-world mathematics problems. He submitted many of these problems to Atanasoff.
Patent dispute
On June 26, 1947, J. Presper Eckert and John Mauchly were the first to file for patent on a digital computing device (ENIAC), much to the surprise of Atanasoff. The ABC had been examined by John Mauchly in June 1941, and Isaac Auerbach, a former student of Mauchly's, alleged that it influenced his later work on ENIAC, although Mauchly denied this. The ENIAC patent did not issue until 1964, and by 1967 Honeywell sued Sperry Rand in an attempt to break the ENIAC patents, arguing that the ABC constituted prior art. The United States District Court for the District of Minnesota released its judgement on October 19, 1973, finding in Honeywell v. Sperry Rand that the ENIAC patent was a derivative of John Atanasoff's invention.
Campbell-Kelly and Aspray conclude: | Atanasoff–Berry computer | Wikipedia | 495 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
The case was legally resolved on October 19, 1973, when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry computer. Judge Larson explicitly stated:
Herman Goldstine, one of the original developers of ENIAC wrote:
Replica
The original ABC was eventually dismantled in 1948, when the university converted the basement to classrooms, and all of its pieces except for one memory drum were discarded.
In 1997, a team of researchers led by Delwyn Bluhm and John Gustafson from Ames Laboratory (located on the Iowa State University campus) finished building a working replica of the Atanasoff–Berry computer at a cost of $350,000 (equivalent to $ in ). The replica ABC was on display in the first floor lobby of the Durham Center for Computation and Communication at Iowa State University and was subsequently exhibited at the Computer History Museum. | Atanasoff–Berry computer | Wikipedia | 190 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
An anchor is a device, normally made of metal, used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin , which itself comes from the Greek ().
Anchors can either be temporary or permanent. Permanent anchors are used in the creation of a mooring, and are rarely moved; a specialist service is normally needed to move or maintain them. Vessels carry one or more temporary anchors, which may be of different designs and weights.
A sea anchor is a drag device, not in contact with the seabed, used to minimise drift of a vessel relative to the water. A drogue is a drag device used to slow or help steer a vessel running before a storm in a following or overtaking sea, or when crossing a bar in a breaking sea.
Anchoring
Anchors achieve holding power either by "hooking" into the seabed, or weight, or a combination of the two. The weight of the anchor chain can be more than that of the anchor and is critical to proper holding. Permanent moorings use large masses (commonly a block or slab of concrete) resting on the seabed. Semi-permanent mooring anchors (such as mushroom anchors) and large ship's anchors derive a significant portion of their holding power from their weight, while also hooking or embedding in the bottom. Modern anchors for smaller vessels have metal flukes that hook on to rocks on the bottom or bury themselves in soft seabed.
The vessel is attached to the anchor by the rode (also called a cable or a warp). It can be made of rope, chain or a combination of rope and chain. The ratio of the length of rode to the water depth is known as the scope. | Anchor | Wikipedia | 361 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Holding ground is the area of sea floor that holds an anchor, and thus the attached ship or boat. Different types of anchor are designed to hold in different types of holding ground. Some bottom materials hold better than others; for instance, hard sand holds well, shell holds poorly. Holding ground may be fouled with obstacles. An anchorage location may be chosen for its holding ground. In poor holding ground, only the weight of an anchor and chain matters; in good holding ground, it is able to dig in, and the holding power can be significantly higher.
The basic anchoring consists of determining the location, dropping the anchor, laying out the scope, setting the hook, and assessing where the vessel ends up. The ship seeks a location that is sufficiently protected; has suitable holding ground, enough depth at low tide and enough room for the boat to swing.
The location to drop the anchor should be approached from down wind or down current, whichever is stronger. As the chosen spot is approached, the vessel should be stopped or even beginning to drift back. The anchor should initially be lowered quickly but under control until it is on the bottom (see anchor windlass). The vessel should continue to drift back, and the cable should be veered out under control (slowly) so it is relatively straight.
Once the desired scope is laid out, the vessel should be gently forced astern, usually using the auxiliary motor but possibly by backing a sail. A hand on the anchor line may telegraph a series of jerks and jolts, indicating the anchor is dragging, or a smooth tension indicative of digging in. As the anchor begins to dig in and resist backward force, the engine may be throttled up to get a thorough set. If the anchor continues to drag, or sets after having dragged too far, it should be retrieved and moved back to the desired position (or another location chosen.) | Anchor | Wikipedia | 380 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Using an anchor weight, kellet or sentinel
Lowering a concentrated, heavy weight down the anchor line – rope or chain – directly in front of the bow to the seabed behaves like a heavy chain rode and lowers the angle of pull on the anchor. If the weight is suspended off the seabed it acts as a spring or shock absorber to dampen the sudden actions that are normally transmitted to the anchor and can cause it to dislodge and drag. In light conditions, a kellet reduces the swing of the vessel considerably. In heavier conditions these effects disappear as the rode becomes straightened and the weight ineffective. Known as an "anchor chum weight" or "angel" in the UK.
Forked moor
Using two anchors set approximately 45° apart, or wider angles up to 90°, from the bow is a strong mooring for facing into strong winds. To set anchors in this way, first one anchor is set in the normal fashion. Then, taking in on the first cable as the boat is motored into the wind and letting slack while drifting back, a second anchor is set approximately a half-scope away from the first on a line perpendicular to the wind. After this second anchor is set, the scope on the first is taken up until the vessel is lying between the two anchors and the load is taken equally on each cable.
This moor also to some degree limits the range of a vessel's swing to a narrower oval. Care should be taken that other vessels do not swing down on the boat due to the limited swing range.
Bow and stern
(Not to be mistaken with the Bahamian moor, below.) In the bow and stern technique, an anchor is set off each the bow and the stern, which can severely limit a vessel's swing range and also align it to steady wind, current or wave conditions. One method of accomplishing this moor is to set a bow anchor normally, then drop back to the limit of the bow cable (or to double the desired scope, e.g. 8:1 if the eventual scope should be 4:1, 10:1 if the eventual scope should be 5:1, etc.) to lower a stern anchor. By taking up on the bow cable the stern anchor can be set. After both anchors are set, tension is taken up on both cables to limit the swing or to align the vessel. | Anchor | Wikipedia | 482 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Bahamian moor
Similar to the above, a Bahamian moor is used to sharply limit the swing range of a vessel, but allows it to swing to a current. One of the primary characteristics of this technique is the use of a swivel as follows: the first anchor is set normally, and the vessel drops back to the limit of anchor cable. A second anchor is attached to the end of the anchor cable, and is dropped and set. A swivel is attached to the middle of the anchor cable, and the vessel connected to that.
The vessel now swings in the middle of two anchors, which is acceptable in strong reversing currents, but a wind perpendicular to the current may break out the anchors, as they are not aligned for this load.
Backing an anchor
Also known as tandem anchoring, in this technique two anchors are deployed in line with each other, on the same rode. With the foremost anchor reducing the load on the aft-most, this technique can develop great holding power and may be appropriate in "ultimate storm" circumstances. It does not limit swinging range, and might not be suitable in some circumstances. There are complications, and the technique requires careful preparation and a level of skill and experience above that required for a single anchor.
Kedging
Kedging or warping is a technique for moving or turning a ship by using a relatively light anchor.
In yachts, a kedge anchor is an anchor carried in addition to the main, or bower, anchor, and usually stowed aft. Every yacht should carry at least two anchors – the main or bower anchor and a second lighter kedge anchor. It is used occasionally when it is necessary to limit the turning circle as the yacht swings when it is anchored, such as in a narrow river or a deep pool in an otherwise shallow area. Kedge anchors are sometimes used to recover vessels that have run aground.
For ships, a kedge may be dropped while a ship is underway, or carried out in a suitable direction by a tender or ship's boat to enable the ship to be winched off if aground or swung into a particular heading, or even to be held steady against a tidal or other stream.
Historically, it was of particular relevance to sailing warships that used them to outmaneuver opponents when the wind had dropped but might be used by any vessel in confined, shoal water to place it in a more desirable position, provided she had enough manpower. | Anchor | Wikipedia | 495 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Club hauling
Club hauling is an archaic technique. When a vessel is in a narrow channel or on a lee shore so that there is no room to tack the vessel in a conventional manner, an anchor attached to the lee quarter may be dropped from the lee bow. This is deployed when the vessel is head to wind and has lost headway. As the vessel gathers sternway the strain on the cable pivots the vessel around what is now the weather quarter turning the vessel onto the other tack. The anchor is then normally cut away (the ship's momentum prevents recovery without aborting the maneuver).
Multiple anchor patterns
When it is necessary to moor a ship or floating platform with precise positioning and alignment, such as when drilling the seabed, for some types of salvage work, and for some types of diving operation, several anchors are set in a pattern which allows the vessel to be positioned by shortening and lengthening the scope of the anchors, and adjusting the tension on the rodes. The anchors are usually laid in prearranged positions by an anchor tender, and the moored vessel uses its own winches to adjust position and tension.
Similar arrangements are used for some types of single buoy moorings, like the catenary anchor leg mooring (CALM) used for loading and unloading liquid cargoes.
Weighing anchor
Since all anchors that embed themselves in the bottom require the strain to be along the seabed, anchors can be broken out of the bottom by shortening the rope until the vessel is directly above the anchor; at this point the anchor chain is "up and down", in naval parlance. If necessary, motoring slowly around the location of the anchor also helps dislodge it. Anchors are sometimes fitted with a trip line attached to the crown, by which they can be unhooked from underwater hazards.
The term aweigh describes an anchor when it is hanging on the rope and not resting on the bottom. This is linked to the term to weigh anchor, meaning to lift the anchor from the sea bed, allowing the ship or boat to move. An anchor is described as aweigh when it has been broken out of the bottom and is being hauled up to be stowed. Aweigh should not be confused with under way, which describes a vessel that is not moored to a dock or anchored, whether or not the vessel is moving through the water. Aweigh is also often confused with away, which is incorrect.
History
Evolution of the anchor | Anchor | Wikipedia | 503 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
The earliest anchors were probably rocks, and many rock anchors have been found dating from at least the Bronze Age. Pre-European Māori waka (canoes) used one or more hollowed stones, tied with flax ropes, as anchors. Many modern moorings still rely on a large rock as the primary element of their design. However, using pure weight to resist the forces of a storm works well only as a permanent mooring; a large enough rock would be nearly impossible to move to a new location.
The ancient Greeks used baskets of stones, large sacks filled with sand, and wooden logs filled with lead. According to Apollonius Rhodius and Stephen of Byzantium, anchors were formed of stone, and Athenaeus states that they were also sometimes made of wood. Such anchors held the vessel merely by their weight and by their friction along the bottom.
Fluked anchors
Iron was afterwards introduced for the construction of anchors, and an improvement was made by forming them with teeth, or "flukes", to fasten themselves into the bottom. This is the iconic anchor shape most familiar to non-sailors.
This form has been used since antiquity. The Roman Nemi ships of the 1st century AD used this form. The Viking Ladby ship (probably 10th century) used a fluked anchor of this type, made of iron, which would have had a wooden stock mounted perpendicular to the shank and flukes to make the flukes contact the bottom at a suitable angle to hook or penetrate.
Admiralty anchor
The Admiralty Pattern anchor, or simply "Admiralty", also known as a "Fisherman", consists of a central shank with a ring or shackle for attaching the rode (the rope, chain, or cable connecting the ship and the anchor). At the other end of the shank there are two arms, carrying the flukes, while the stock is mounted to the shackle end, at ninety degrees to the arms. When the anchor lands on the bottom, it generally falls over with the arms parallel to the seabed. As a strain comes onto the rope, the stock digs into the bottom, canting the anchor until one of the flukes catches and digs into the bottom. | Anchor | Wikipedia | 449 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
The Admiralty Anchor is an entirely independent reinvention of a classical design, as seen in one of the Nemi ship anchors. This basic design remained unchanged for centuries, with the most significant changes being to the overall proportions, and a move from stocks made of wood to iron stocks in the late 1830s and early 1840s.
Since one fluke always protrudes up from the set anchor, there is a great tendency of the rode to foul the anchor as the vessel swings due to wind or current shifts. When this happens, the anchor may be pulled out of the bottom, and in some cases may need to be hauled up to be re-set. In the mid-19th century, numerous modifications were attempted to alleviate these problems, as well as improve holding power, including one-armed mooring anchors. The most successful of these patent anchors, the Trotman Anchor, introduced a pivot at the centre of the crown where the arms join the shank, allowing the "idle" upper arm to fold against the shank. When deployed the lower arm may fold against the shank tilting the tip of the fluke upwards, so each fluke has a tripping palm at its base, to hook on the bottom as the folded arm drags along the seabed, which unfolds the downward oriented arm until the tip of the fluke can engage the bottom.
Handling and storage of these anchors requires special equipment and procedures. Once the anchor is hauled up to the hawsepipe, the ring end is hoisted up to the end of a timber projecting from the bow known as the cathead. The crown of the anchor is then hauled up with a heavy tackle until one fluke can be hooked over the rail. This is known as "catting and fishing" the anchor. Before dropping the anchor, the fishing process is reversed, and the anchor is dropped from the end of the cathead.
Stockless anchor
The stockless anchor, patented in England in 1821, represented the first significant departure in anchor design in centuries. Although their holding-power-to-weight ratio is significantly lower than admiralty pattern anchors, their ease of handling and stowage aboard large ships led to almost universal adoption. In contrast to the elaborate stowage procedures for earlier anchors, stockless anchors are simply hauled up until they rest with the shank inside the hawsepipes, and the flukes against the hull (or inside a recess in the hull called the anchor box). | Anchor | Wikipedia | 500 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
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