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Subfamily Chasmosaurinae
Agathaumas - ( Wyoming , USA )
Agujaceratops - ( Texas , USA )
Anchiceratops - ( Alberta , Canada )
Arrhinoceratops - ( Alberta , Canada )
Chasmosaurus - ( Alberta , Canada )
Coahuilaceratops - ( Coahuila , Mexico )
? Dysganus - ( Montana , USA )
Judiceratops - ( Montana , USA )
Kosmoceratops - ( Utah , USA )
Medusaceratops - ( Montana , USA )
Mojoceratops - ( Alberta & Saskatchewan , Canada )
Pentaceratops - ( New Mexico , USA )
? Polyonax - ( Colorado , USA )
Utahceratops - ( Utah , USA )
Vagaceratops - ( Alberta , Canada )
Tribe Triceratopsini
Eotriceratops - ( Alberta , Canada )
Nedoceratops - ( Wyoming , USA )
Ojoceratops - ( New Mexico , USA )
Regaliceratops - ( Alberta , Canada )
Tatankaceratops - ( South Dakota , USA )
Titanoceratops - ( New Mexico , USA )
Torosaurus - ( Wyoming , Montana , South Dakota , North Dakota , & Utah , USA & Saskatchewan , Canada )
Triceratops - ( Montana & Wyoming , USA & Saskatchewan & Alberta , Canada )
Possible ceratopsians from the Southern Hemisphere include the Australian Serendipaceratops , known from an ulna , and Notoceratops from Argentina is known from a single toothless jaw ( which has been lost ) . Craspedodon from the Late Cretaceous ( Santonian ) of Belgium may also be a ceratopsian , specifically a neoceratopsian closer to ceratopsoidea than protoceratopsidae . Possible leptoceratopsid remains have also been described from the early Campanian of Sweden .
= = = Phylogeny = = =
Paleontologists today agree on the overall structure of the ceratopsian family tree , although there are differences on individual taxa . There have been several cladistic studies performed on basal ceratopsians since 2000 . None have used every taxon listed above and many of the differences between the studies are still unresolved .
In clade @-@ based phylogenetic taxonomy , Ceratopsia is often defined to include all marginocephalians more closely related to Triceratops than to Pachycephalosaurus . Under this definition , the most basal known ceratopsians are Yinlong , from the Late Jurassic Period , along with Chaoyangsaurus and the family Psittacosauridae , from the Early Cretaceous Period , all of which were discovered in northern China or Mongolia . The rostral bone and flared jugals are already present in all of these forms , indicating that even earlier ceratopsians remain to be discovered .
The clade Neoceratopsia includes all ceratopsians more derived than psittacosaurids . Another subset of neoceratopsians is called Coronosauria , which currently includes all ceratopsians more derived than Auroraceratops . Coronosaurs show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head . Within Coronosauria , three groups are generally recognized , although the membership of these groups varies somewhat from study to study and some animals may not fit in any of them . One group can be called Protoceratopsidae and includes Protoceratops and its closest relatives , all Asian . Another group , Leptoceratopsidae , includes mostly North American animals that are more closely related to Leptoceratops . The Ceratopsoidea includes animals like Zuniceratops , which are more closely related to the family Ceratopsidae . This last family includes Triceratops and all the large North American ceratopsians and is further divided into the subfamilies Centrosaurinae and Ceratopsinae ( also known as Chasmosaurinae ) .
= = = = Farke phylogeny = = = =
Andrew Farke and his colleagues in 2014 published a description of a new neoceratopsian , Aquilops americanus , through the peer @-@ reviewed science journal PLOS ONE . They analysed their taxa as well as most other primitive ceratopsians to get a consensus cladogram . They created their own data matrix and through it found that many groups of ceratopsians could be supported , and that Aquilops was a basal neoceratopsian that could potentially be a protoceratopsid , leptoceratopsid , or ceratopsid , although any one of these groups would have a large ghost lineage with Aquilops .
Their study also found an equal consensus cladogram finding Ajkaceratops not as a neoceratopsian but a protoceratopsid . Nothing else about the cladograms changed .
= = = = Xu / Makovicky / Chinnery Phylogeny = = = =
Xu Xing of the Chinese Institute of Vertebrate Paleontology and Paleoanthropology ( IVPP ) in Beijing , along with Peter Makovicky , formerly of the American Museum of Natural History ( AMNH ) in New York City and others , published a cladistic analysis in the 2002 description of Liaoceratops . This analysis is very similar to one published by Makovicky in 2001 . Makovicky , who currently works at the Field Museum of Natural History in Chicago , also included this analysis in his 2002 doctoral thesis . Xu and other colleagues added Yinlong to this analysis in 2006 .
Brenda Chinnery , formerly of the Museum of the Rockies in Bozeman , Montana , independently described Prenoceratops in 2005 and published a new phylogeny . In 2006 , Makovicky and Mark Norell of the AMNH incorporated Chinnery 's analysis into their own and also added Yamaceratops , although they were not able to include Yinlong . The cladogram presented below is a combination of Xu , Makovicky , and their colleagues ' most recent work .
Chaoyangsaurus is recovered in a more basal position than Psittacosauridae , although Chinnery 's original analysis finds it within Neoceratopsia . Protoceratopsidae is considered to be the sister group of Ceratopsoidea . The fragmentary Asiaceratops was included in these studies and is found to have a variable position , either as a basal neoceratopsian or as a leptoceratopsid , most likely due to the amount of missing information . Removal of Asiaceratops stabilizes the entire cladogram .
Makovicky 's latest analysis includes IVPP V12722 ( " Xuanhuasaurus " ) , a Late Jurassic ceratopsian from China that , at the time , was awaiting publication , but has since been published as Xuanhuaceratops . Kulceratops and Turanoceratops are considered nomina dubia in this study . Makovicky believes Lamaceratops , Magnirostris , and Platyceratops to be junior synonyms of Bagaceratops , and Bainoceratops to be synonymous with Protoceratops .
= = = = You / Dodson Phylogeny = = = =
You Hailu of Beijing 's Chinese Academy of Geological Sciences , was a co @-@ author with Xu and Makovicky in 2002 but , in 2003 , he and Peter Dodson from the University of Pennsylvania published a separate analysis . The two presented this analysis again in 2004 . In 2005 , You and three others , including Dodson , published on Auroraceratops and inserted this new dinosaur into their phylogeny .
In contrast to the previous analysis , You and Dodson find Chaoyangsaurus to be the most basal neoceratopsian , more derived than Psittacosaurus , while Leptoceratopsidae , not Protoceratopsidae , is recovered as the sister group of Ceratopsidae . This study includes Auroraceratops , but lacks seven taxa found in Xu and Makovicky 's work , so it is unclear how comparable the two studies are . Asiaceratops and Turanoceratops are each considered nomina dubia and not included . Along with Dong Zhiming , You described Magnirostris in 2003 , but to date has not included it in any of his cladograms .
= = Paleobiology = =
= = = Biogeography = = =
Ceratopsia appears to have originated in Asia , as all of the earliest members are found there . Fragmentary remains , including teeth , which appear to be neoceratopsian , are found in North America from the Albian stage ( 112 to 100 million years ago ) , indicating that the group had dispersed across what is now the Bering Strait by the middle of the Cretaceous Period . Almost all leptoceratopsids are North American , aside from Udanoceratops , which may represent a separate dispersal event , back into Asia . Ceratopsids and their immediate ancestors , such as Zuniceratops , were unknown outside of western North America , and were presumed endemic to that continent . The traditional view that ceratopsoids originated in North America was called into question by the 2009 discovery of better specimens of the dubious Asian form Turanoceratops , which confirmed it as a ceratopsid . It is unknown whether this indicates ceratopsids actually originated in Asia , or if the Turanoceratops immigrated from North America .
= = = Individual variation = = =
Unlike almost all other dinosaur groups , skulls are the most commonly preserved elements of ceratopsian skeletons and many species are known only from skulls . There is a great deal of variation between and even within ceratopsian species . Complete growth series from embryo to adult are known for Psittacosaurus and Protoceratops , allowing the study of ontogenetic variation in these species . Significant sexual dimorphism has been noted in Protoceratops and several ceratopsids .
= = = Ecological role = = =
Psittacosaurus and Protoceratops are the most common dinosaurs in the different Mongolian sediments where they are found . Triceratops fossils are far and away the most common dinosaur remains found in the latest Cretaceous rocks in the western United States , making up as much as 5 / 6ths of the large dinosaur fauna in some areas . These facts indicate that some ceratopsians were the dominant herbivores in their environments .
Some species of ceratopsians , especially Centrosaurus and its relatives , appear to have been gregarious , living in herds . This is suggested by bonebed finds with the remains of many individuals of different ages . Like modern migratory herds , they would have had a significant effect on their environment , as well as serving as a major food source for predators .
Although ceratopsians are generally considered herbivorous , a few paleontologists , such as Darren Naish and Mark Witton , have speculated online that at least some ceratopsians may have been opportunistically omnivorous .
= = = Posture and locomotion = = =
Most restorations of ceratopsians show them with erect hindlimbs but semi @-@ sprawling forelimbs , which suggest that they were not fast movers . But Paul and Christiansen ( 2000 ) argued that at least the later ceratopsians had upright forelimbs and the larger species may have been as fast as rhinos , which can run at up to 56 km or 35 miles per hour .
= = = Daily activity patterns = = =
A nocturnal lifestyle has been suggested for the primitive ceratopsian Protoceratops . However , comparisons between the scleral rings of Protoceratops and Psittacosaurus and modern birds and reptiles indicate that they may have been cathemeral , active throughout the day at short intervals .
= = = Paleopathology = = =
Activity @-@ related bone fractures have been documented in ceratopsians . Periostitis has also been documented in the shoulder blade of a ceratopsian .
= = Timeline of genera = =
= Truth in Numbers ? =
Truth in Numbers ? Everything , According to Wikipedia is a 2010 American documentary film that explores the history and cultural implications of the online , user @-@ editable encyclopedia Wikipedia . The film considers the question of whether all individuals or just experts should be tasked with editing an encyclopedia .
The site 's history and background is given , along with commentary from Wikipedia founders Jimmy Wales and Larry Sanger . Commentators that appear in the film include author Howard Zinn , Len Downie of The Washington Post , Bob Schieffer of CBS News , former Encyclopædia Britannica chief Robert McHenry and former Central Intelligence Agency director James Woolsey . The documentary discusses incidents that shed a negative light on Wikipedia , including the Essjay controversy and the Wikipedia biography controversy .
The long @-@ delayed film premiered at Wikimania 2010 in Gdańsk in July 2010 , and was screened at the Paley Center for Media in New York City in October 2010 . It was shown as part of the Savannah Film Festival on November 3 , 2010 , at Savannah College of Art and Design 's Trustees Theater . Truth in Numbers ? received a mixed reception , with favorable commentary from author Ted Leonsis , in the AOL publication Urlesque , and coverage at the Savannah Film Festival by Carlos Serrano of District .
= = Contents = =
Truth in Numbers ? Everything , According to Wikipedia , an American documentary film , explores the history and cultural implications of Wikipedia . The film presents Wikipedia as a new form of communication and cultural dialog . The directors attempt to answer the question of whether ordinary individuals should be tasked with collecting knowledge for presentation online , or this should be relegated solely to academic scholars in specific fields . The film gives an overview of the history of the enterprise , as well as biographical information on founder Jimmy Wales . Wales is shown discussing Wikipedia with an Indian reader , who points out an inaccuracy in an article . Wales proceeds to show the reader how to click the " edit " tab on the website . Wikipedia founder Larry Sanger is featured in the documentary and speaks critically about the website 's embracing of editors from the general public as opposed to soliciting expert contributors .
Journalism and media commentators who appear and are interviewed in the film include author Howard Zinn ; Len Downie , ( executive editor of The Washington Post ) ; Bob Schieffer ( CBS News ) ; Robert McHenry ( former chief of Encyclopædia Britannica ) ; James Woolsey ( former director of the Central Intelligence Agency ) ; Chris Wilson ( reporter for Slate Magazine ) ; Cade Metz ( reporter for The Register who has written critically about Wikipedia ) ; Richard Branson and Noam Chomsky . The film documents an initiative in India and Africa called " Wikipedia Academies " . Controversies discussed in the film include the Essjay controversy , where a member of Wikipedia made false assertions about his academic background ; and the Wikipedia biography controversy , where false statements were inserted into the Wikipedia entry for journalist John Seigenthaler . Musician KRS @-@ One comments about the site after reading his biography on Wikipedia : " I can say to you , these are the facts but they are not true . "
= = Production = =
= = = Conception = = =
The idea for the film originated from a suggestion by Michael Ferris Gibson , who had made the 2005 documentary 24 Hours on Craigslist . Gibson , a producer on the film , met with co @-@ director Nic Hill . Gibson financed Hill 's travels while making the film . The working title for the film was Truth in Numbers : The Wikipedia Story . Gibson chose to finance the film through a request for funding from Internet visitors ; the initial request drew in US $ 20 @,@ 000 in initial investment . The production team made their initial work on the project known to Internet viewers via the website www.wikidocumentary.org. Another collaborative website focused on the documentary was formed at Wikia , located at wikidocumentary.wikia.com. Regarding his financing strategy , Gibson commented to the San Francisco Chronicle , that smaller incremental donations from multiple individuals showed genuine interest in his initiative .