Editing Triceratops (section)

==Paleoecology==
[[File:Upper Cretaceous Hell Creek dinosaur census.png|thumb|left|Pie chart of the time averaged census for large-bodied dinosaurs from the entire [[Hell Creek Formation]] in the study area]]
''Triceratops'' lived during the Late Cretaceous of western North America, its fossils coming from the [[Evanston Formation]], [[Scollard Formation]], [[Laramie Formation]], [[Lance Formation]], [[Denver Formation]], and [[Hell Creek Formation]].<ref name="weishampel"/> These fossil formations date back to the time of the [[Cretaceous–Paleogene extinction event]], which has been dated to 66&nbsp;±&nbsp;0.07 million years ago.<ref name="hcfage">{{Cite journal | doi = 10.1016/j.epsl.2011.03.008| title = Astronomical calibration of the Maastrichtian (Late Cretaceous)| journal = Earth and Planetary Science Letters| volume = 305| issue = 3–4| pages = 328–340| year = 2011| last1 = Husson | first1 = D. E. | last2 = Galbrun | first2 = B. | last3 = Laskar | first3 = J. | last4 = Hinnov | first4 = L. A. | last5 = Thibault | first5 = N. | last6 = Gardin | first6 = S. | last7 = Locklair | first7 = R. E. | bibcode = 2011E&PSL.305..328H}}</ref> Many animals and plants have been found in these formations, but mostly from the Lance Formation and Hell Creek Formation.<ref name="weishampel"/> ''Triceratops'' was one of the last ceratopsian genera to appear before the end of the Mesozoic. The related ''[[Torosaurus]]'' and more distantly related diminutive ''[[Leptoceratops]]'' were also present, though their remains have been rarely encountered.<ref name="Dodhorned"/> Isotopic analysis suggests ''Triceratops'' specimens from DTB (Darnell Triceratops Bonebed) could’ve inhabited freshwater floodplains, although the it likely wasn’t restricted to one environment.<ref name=":1" />

Theropods from these formations include genera of [[dromaeosaurids]], [[tyrannosaurids]], [[ornithomimids]], [[troodontids]],<ref name="weishampel">{{Cite book |title=The Dinosauria |last1=Weishampel |first1=D.B. |last2=Dodson |first2=Peter |last3=Osmólska |first3=H. |publisher=University of California Press |year=2004 |isbn=978-0-520-24209-8 |edition=Second |location=Berkeley |pages=861}}</ref> [[avialans]],<ref name="pnas">{{Cite journal | doi = 10.1073/pnas.1110395108| title = Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary| journal = Proceedings of the National Academy of Sciences| volume = 108| issue = 37| pages = 15253–15257| year = 2011| last1 = Longrich | first1 = N. R.| last2 = Tokaryk | first2 = T.| last3 = Field | first3 = D. J.| bibcode = 2011PNAS..10815253L | pmid=21914849 | pmc=3174646| doi-access = free}}</ref> and [[caenagnathids]].<ref name="Anzu">{{Cite journal | doi = 10.1371/journal.pone.0092022| pmid = 24647078| title = A New Large-Bodied Oviraptorosaurian Theropod Dinosaur from the Latest Cretaceous of Western North America| journal = PLOS ONE| volume = 9| issue = 3| pages = e92022| year = 2014| last1 = Lamanna | first1 = M. C. | last2 = Sues | first2 = H. D. | last3 = Schachner | first3 = E. R. | last4 = Lyson | first4 = T. R. | bibcode = 2014PLoSO...992022L | pmc=3960162| doi-access = free}} {{open access}}</ref> Dromaeosaurids from the Hell Creek Formation are ''[[Acheroraptor]]'' and ''[[Dakotaraptor]]''. Indeterminate dromaeosaurs are known from other fossil formations. Common teeth previously referred to ''[[Dromaeosaurus]]'' and ''[[Saurornitholestes]]'' were considered to be those of ''Acheroraptor''.<ref name="Acheroraptor">{{Cite journal | last1 = Evans | first1 = D. C. | last2 = Larson | first2 = D. W. | last3 = Currie | first3 = P. J. | doi = 10.1007/s00114-013-1107-5 | title = A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America | journal = Naturwissenschaften | volume = 100 | issue = 11 | pages = 1041–1049 | year = 2013 | pmid =  24248432| bibcode = 2013NW....100.1041E | s2cid = 14978813 }}</ref> The tyrannosaurids from the formation are ''[[Nanotyrannus]]'' and ''[[Tyrannosaurus]]'', although the former is most likely a junior synonym of the latter. Among ornithomimids are the genera ''[[Struthiomimus]]'' and ''[[Ornithomimus]]''.<ref name="weishampel" /> An undescribed animal named "[[Orcomimus]]" could be from the formation.<ref name="tb1997">{{cite journal|last=Triebold|first=M.|year=1997|title=The Sandy site: Small dinosaurs from the Hell Creek Formation of South Dakota|editor-last=Wolberg|editor-first=D.|editor2-last=Stump|editor2-first=E.|editor3-last=Rosenberg|editor3-first=G.|journal=Dinofest International: Proceedings of a Symposium|pages=245–248}}</ref> Troodontids are only represented by ''[[Pectinodon]]'' and ''[[Paronychodon]]'' in the Hell Creek Formation with a possible species of ''[[Troodon]]'' from the Lance Formation. One species of unknown [[coelurosaur]] is known from teeth in the Hell Creek and similar formations by a single species, ''[[Richardoestesia]]''. Only three [[oviraptorosaur]]s are from the Hell Creek Formation: ''[[Anzu wyliei|Anzu]]'', ''[[Leptorhynchos (dinosaur)|Leptorhynchos]]''<ref name="Anzu" /> and a giant species of caenagnathid, very similar to ''[[Gigantoraptor]]'', from South Dakota. However, only fossilized foot prints were discovered.<ref>{{cite web|url=http://rmdrc.blogspot.com/2013/12/giant-oviraptor-tracks-from-hell-creek.html|last1=Maltese|first1=Anthony|title=Giant Oviraptor Tracks from the Hell Creek|publisher=RMDRC paleo lab|access-date=December 17, 2013|date=December 17, 2013|archive-date=November 12, 2020|archive-url=https://web.archive.org/web/20201112003952/http://rmdrc.blogspot.com/2013/12/giant-oviraptor-tracks-from-hell-creek.html|url-status=live}}</ref> The avialans known from the formation are ''[[Avisaurus]]'',<ref name="weishampel"/> multiple species of ''[[Brodavis]]'',<ref name="brodavis">{{Cite journal | doi = 10.1016/j.palwor.2012.02.005| title = A new evolutionary lineage of diving birds from the Late Cretaceous of North America and Asia| journal = [[Palaeoworld]]| volume = 21| pages = 59–63| year = 2012| last1 = Martin | first1 = L. D. | last2 = Kurochkin | first2 = E. N. | last3 = Tokaryk | first3 = T. T. }}</ref> and several other species of [[hesperornithoforms]], as well as several species of true [[bird]]s, including ''[[Cimolopteryx]]''.<ref name="pnas"/>

[[File:Hell Creek dinosaurs and pterosaurs by durbed.jpg|thumb|right|''Triceratops'' and other animals of the Hell Creek Formation]]
[[Ornithischia]]ns are abundant in the Scollard, Laramie, Lance, Denver, and Hell Creek Formation. The main groups of ornithischians are [[ankylosauria]]ns, [[ornithopod]]s, [[ceratopsia]]ns, and [[pachycephalosauria]]ns. Three ankylosaurians are known: ''[[Ankylosaurus]]'', ''[[Denversaurus]]'', and possibly a species of ''[[Edmontonia]]'' or an undescribed genus. Multiple genera of ceratopsians are known from the formation other than ''Triceratops''. These include the [[leptoceratopsid]] ''[[Leptoceratops]]'' and the [[chasmosaurine]] [[ceratopsids]] ''[[Torosaurus]]'',<ref name="weishampel" /> ''[[Nedoceratops]]'', and ''[[Tatankaceratops]]''.<ref name="tatanka">{{cite book|last1=Ott|first1=C.J.|last2=Larson|first2=P.L.|year=2010|chapter=A New, Small Ceratopsian Dinosaur from the Latest Cretaceous Hell Creek Formation, Northwest South Dakota, United States: A Preliminary Description|editor-last=Ryan|editor-first=M.J.|editor2-last=Chinnery-Allgeier|editor2-first=B.J.|editor3-last=Eberth|editor3-first=D.A.|title=New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium|location=Bloomington|publisher=Indiana University Press|pages=656}}</ref> Ornithopods are common in the Hell Creek Formation and are known from several species of the [[Thescelosaurinae|thescelosaurine]] ''[[Thescelosaurus]]'' and the [[hadrosaurid]]  ''[[Edmontosaurus]]''.<ref name="weishampel"/><ref name="hcfhadro">{{Cite journal |last1=Campione |first1=N. S. E. |last2=Evans |first2=D. C. |year=2011 |title=Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America |journal=PLOS ONE |volume=6 |issue=9 |pages=e25186 |bibcode=2011PLoSO...625186C |doi=10.1371/journal.pone.0025186 |pmc=3182183 |pmid=21969872|doi-access=free }} {{open access}}</ref> Several [[pachycephalosauria]]ns have been found in the Hell Creek Formation and in similar formations. Among them are the derived [[pachycephalosaurids]] ''[[Stygimoloch]]'',<ref name="weishampel"/> ''[[Dracorex]]'',<ref name="bakker">{{cite journal|last1=Bakker|first1=R.T.|last2=Sullivan|first2=R.M.|last3=Porter|first3=V.|last4=Larson|first4=P.|last5=Saulsbury|first5=S.J.|year=2006|title=''Dracorex hogwartsia'', n. gen., n. sp., a spiked, flat-headed pachycephalosaurid dinosaur from the Upper Cretaceous Hell Creek Formation of South Dakota|editor-last=Lucas|editor-first=S.G.|editor2-last=Sullivan|editor2-first=R.M.|journal=Late Cretaceous Vertebrates from the Western Interior|series=New Mexico Museum of Natural History and Science Bulletin|volume=35|pages=331–345|url=http://econtent.unm.edu/cdm/ref/collection/bulletins/id/710|access-date=January 6, 2015|archive-date=November 19, 2018|archive-url=https://web.archive.org/web/20181119203737/http://econtent.unm.edu/cdm/ref/collection/bulletins/id/710|url-status=live}}</ref> ''[[Pachycephalosaurus]]'',<ref name="weishampel"/> ''[[Sphaerotholus]]'', and an undescribed specimen from North Dakota. The first two might be junior synonyms of ''Pachycephalosaurus''.

[[Mammal]]s are plentiful in the Hell Creek Formation. Groups represented include [[multituberculates]], [[metatheria]]ns, and [[eutheria]]ns. The multituberculates represented include ''[[Paracimexomys]],''<ref name="kj2004">{{Cite book |title=Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure |last1=Kielan-Jaworowska |first1=Zofia |last2=Cifelli |first2=Richard L. |last3=Luo |first3=Zhe-Xi |date=2004 |publisher=Columbia University Press |isbn=978-0-231-11918-4 |location=New York |pages=98–99 |author-link=Zofia Kielan-Jaworowska}}</ref> the [[cimolomyidae|cimolomyids]] ''[[Paressonodon]]'',<ref name="mammal">{{Cite journal |last=Wilson |first=G. P. |year=2013 |title=Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: Dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling |journal=Paleobiology |volume=39 |issue=3 |pages=429–469 |doi=10.1666/12041|bibcode=2013Pbio...39..429W |s2cid=36025237 |url=http://www.bioone.org/doi/pdf/10.4202/app.00117.2014 }}</ref> ''[[Meniscoessus]]'', ''[[Essonodon]]'', ''[[Cimolomys]]'', ''[[Cimolodon]]'', and ''[[Cimexomys]]'', and the [[neoplagiaulacidae|neoplagiaulacids]] ''[[Mesodma]]'' and ''[[Neoplagiaulax]]''. The metatherians are represented by the [[alphadontidae|alphadontids]] ''[[Alphadon]]'', ''[[Protalphodon]]'', and ''[[Turgidodon]]'', the [[pediomyidae|pediomyids]] ''[[Pediomys]]'',<ref name="kj2004"/> ''[[Protolambda]]'', and ''[[Leptalestes]]'',<ref name="mammalshcf">{{Cite journal |last1=Archibald |first1=J. D. |last2=Zhang |first2=Y. |last3=Harper |first3=T. |last4=Cifelli |first4=R. L. |year=2011 |title=Protungulatum, Confirmed Cretaceous Occurrence of an Otherwise Paleocene Eutherian (Placental?) Mammal |journal=Journal of Mammalian Evolution |volume=18 |issue=3 |pages=153–161 |doi=10.1007/s10914-011-9162-1|s2cid=16724836 }}</ref> the [[stagodontidae|stagodontid]] ''[[Didelphodon]]'',<ref name="kj2004"/> the [[deltatheridiidae|deltatheridiid]] ''[[Nanocuris]]'', the [[herpetotheriidae|herpetotheriid]] ''[[Nortedelphys]]'',<ref name="mammal"/> and the [[glasbiidae|glasbiid]] ''[[Glasbius]]''. A few eutherians are known, being represented by ''[[Alostera]]'',<ref name="kj2004"/> ''[[Protungulatum]]'',<ref name="mammalshcf"/> the [[cimolestidae|cimolestids]] ''[[Cimolestes]]'' and ''[[Batodon]]'', the [[gypsonictopsidae|gypsonictopsid]] ''[[Gypsonictops]]'' , and the possible [[nyctitheriidae|nyctitheriid]] ''[[Paranyctoides]]''.<ref name="kj2004"/>

[[File:Knight Triceratops.jpg|thumb|1901 illustration by [[Charles R. Knight]]]]