Editing Triceratops (section)

==Description==
===Size===
[[File:Triceratops Scale V1.svg|thumb|Size comparison with ''T. horridus'' in blue and ''T. prorsus'' in red]]
''Triceratops'' was a very large animal, measuring around {{cvt|8|-|9|m}} in length and weighing up to {{Convert|6|-|10|MT|ST}}.<ref name="paul2010" /><ref>{{cite book |last=Holtz |first=Thomas R. Jr. |year=2011 |title=Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages |url=http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf |quote=Winter 2011 Appendix |archive-date=August 12, 2017 |access-date=August 2, 2022 |archive-url=https://web.archive.org/web/20170812011954/http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf |url-status=live }}</ref><ref>{{cite journal |last1=Stein |first1=Walter W. |title=TAKING COUNT: A Census of Dinosaur Fossils Recovered From the Hell Creek and Lance Formations (Maastrichtian). |journal=The Journal of Paleontological Sciences |date=2019 |volume=8 |pages=1–42 |url=https://www.aaps-journal.org/pdf/JPS.C.2019.01a.pdf |archive-date=October 8, 2024 |access-date=April 21, 2024 |archive-url=https://web.archive.org/web/20241008104837/https://www.aaps-journal.org/pdf/JPS.C.2019.01a.pdf |url-status=live }}</ref> A specimen of ''T.&nbsp;horridus'' named Kelsey measured {{convert|22|-|24|ft|order=flip|sp=us}} long, has a {{convert|6.5|ft|order=flip|adj=on|sp=us|sigfig=1}} skull, stood about {{convert|7.5|ft|order=flip|sp=us}} tall, and was estimated by the [[Black Hills Institute]] to weigh approximately {{convert|5.4|MT|ST}}.<ref>{{Cite web |url=https://www.bhigr.com/pages/info/info_klsy.htm |title=A ''Triceratops'' Named 'Kelsey' |website=www.bhigr.com |access-date=December 22, 2017 |archive-date=December 23, 2017 |archive-url=https://web.archive.org/web/20171223102110/https://www.bhigr.com/pages/info/info_klsy.htm |url-status=live }}</ref><ref>{{Cite web |website=www.bhigr.com|title=Kesley the ''Triceratops''|url=https://bhigr.com/wp-content/uploads/2022/04/KelseySkeleton_03-copy-scaled.jpg}}</ref>

===Skull===
[[File:Triceratops skull frills.jpg|thumb|left|upright|Front view of skull with a prominent [[epoccipital]] fringe, [[Houston Museum of Natural Science]]]]
Like all [[Chasmosaurinae|chasmosaurines]], ''Triceratops'' had a large skull relative to its body size, among the largest of all land animals. The largest-known skull, specimen [[Museum of Western Colorado|MWC]] 7584 (formerly [[Brigham Young University|BYU]] 12183), is estimated to have been {{convert|2.5|m|ft|sp=us}} in length when complete<ref name="ScanHorn2010">{{Cite journal |last1=Scannella |first1=J. |last2=Horner |first2=J.R. |year=2010 |title=''Torosaurus'' Marsh, 1891, is ''Triceratops'' Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny |journal=Journal of Vertebrate Paleontology |volume=30 |issue=4 |pages=1157–1168 |doi=10.1080/02724634.2010.483632|bibcode=2010JVPal..30.1157S |s2cid=86767957 }}</ref> and could reach almost a third of the length of the entire animal.<ref name="Lambert93">{{Cite book |title=The Ultimate Dinosaur Book |last=Lambert |first=D. |publisher=Dorling Kindersley, New York |year=1993 |isbn=978-1-56458-304-8 |pages=[https://archive.org/details/ultimatedinosaur00lamb/page/152 152–167] |url=https://archive.org/details/ultimatedinosaur00lamb/page/152 }}</ref>

The front of the head was equipped with a large beak in front of its teeth. The core of the top beak was formed by a special rostral bone. Behind it, the [[premaxilla]]e bones were located, embayed from behind by very large, circular nostrils. In chasmosaurines, the premaxillae met on their midline in a complex bone plate, the rear edge of which was reinforced by the "narial strut". From the base of this strut, a triangular process jutted out into the nostril. ''Triceratops'' differs from most relatives in that this process was hollowed out on the outer side. Behind the toothless premaxilla, the [[maxilla]] bore thirty-six to forty tooth positions, in which three to five teeth per position were vertically stacked. The teeth were closely appressed, forming a "dental battery" curving to the inside. The skull bore a single horn on the snout above the nostrils. In ''Triceratops'', the nose horn is sometimes recognisable as a separate ossification, the epinasal.<ref name="Dino2"/> 

The skull also featured a pair of supraorbital "brow" horns approximately {{convert|1|m|ft|sp=us}} long, with one above each eye.<ref>{{cite news|url=https://news.google.com/newspapers?nid=894&dat=20031118&id=OCNTAAAAIBAJ&pg=6720,2967799|title=Denver museum unveils 7-foot-long, 1,000-pound Triceratops skull|publisher=The Daily Courier|date=November 18, 2003|access-date=December 26, 2013|archive-date=May 19, 2021|archive-url=https://web.archive.org/web/20210519173018/https://news.google.com/newspapers?nid=894&dat=20031118&id=OCNTAAAAIBAJ&pg=6720,2967799|url-status=live}}</ref><ref>{{Cite journal |last1=Scannella |first1=John B. |last2=Fowler |first2=Denver W. |last3=Goodwin |first3=Mark B. |last4=Horner |first4=John R. |date=July 15, 2014 |title=Evolutionary trends in Triceratops from the Hell Creek Formation, Montana |journal=Proceedings of the National Academy of Sciences |language=en |volume=111 |issue=28 |pages=10245–10250 |doi=10.1073/pnas.1313334111 |issn=0027-8424 |pmid=24982159 |pmc=4104892|bibcode=2014PNAS..11110245S |doi-access=free }}</ref> The [[jugal bone]]s pointed downward at the rear sides of the skull and were capped by separate epijugals. With ''Triceratops'', these were not particularly large and sometimes touched the quadratojugals. The bones of the skull roof were fused and by a folding of the [[frontal bone]]s, a "double" skull roof was created. In ''Triceratops'', some specimens show a [[fontanelle]], an opening in the upper roof layer. The cavity between the layers invaded the bone cores of the brow horns.<ref name="Dino2"/>

[[File:Back_and_below_of_Triceratops_skull_-_Fergus_County_Montana_-_Museum_of_the_Rockies_-_2013-07-08.jpg|thumb|Back of skull, showing rounded joint which connected the head and neck]]
At the rear of the skull, the outer [[squamosal bone]]s and the inner [[parietal bone]]s grew into a relatively short, bony frill, adorned with [[epoccipitals]] in young specimens. These were low triangular processes on the frill edge, representing separate skin ossifications or [[osteoderms]]. Typically, with ''Triceratops'' specimens, there are two epoccipitals present on each parietal bone, with an additional central process on their border. Each squamosal bone had five processes. Most other ceratopsids had large parietal [[Fenestra (anatomy)|fenestrae]], openings in their frills, but those of ''Triceratops'' were noticeably solid,<ref>{{cite news |url=https://news.google.com/newspapers?nid=2249&dat=19011024&id=U5I-AAAAIBAJ&pg=5758,3411357 |title=Making A Triceratops. Science Supplies Missing Part! Of Skeleton |publisher=Boston Evening Transcript |date=October 24, 1901 |access-date=December 26, 2013 |archive-date=May 19, 2021 |archive-url=https://web.archive.org/web/20210519173017/https://news.google.com/newspapers?nid=2249&dat=19011024&id=U5I-AAAAIBAJ&pg=5758,3411357 |url-status=live }}</ref> unless the genus ''[[Torosaurus]]'' represents mature ''Triceratops'' individuals, which it most likely does not. Under the frill, at the rear of the skull, a huge [[occipital condyle]], up to {{convert|106|mm|sp=us}} in diameter, connected the head to the neck.<ref name="Dino2"/>

The lower jaws were elongated and met at their tips in a shared epidentary bone, the core of the toothless lower beak. In the dentary bone, the tooth battery curved to the outside to meet the battery of the upper jaw. At the rear of the lower jaw, the [[articular bone]] was exceptionally wide, matching the general width of the jaw joint.<ref name="Dino2"/> ''T.&nbsp;horridus'' can be distinguished from ''T.&nbsp;prorsus'' by having a shallower snout.<ref name="paul2010">{{cite book | url=https://archive.org/details/princetonfieldgu0000paul/page/265 | title=The Princeton Field Guide to Dinosaurs | publisher=Princeton University Press | last=Paul | first=G. S. | author-link=Gregory S. Paul | year=2010 | pages=[https://archive.org/details/princetonfieldgu0000paul/page/265 265–267] | isbn=978-0-691-13720-9 }}</ref>

===Postcranial skeleton===
[[File:Triceratops Raymond National Museum of Nature and Science.jpg|thumb|left|Specimen nicknamed "Raymond" that preserves the natural, non-pronated pose of the forelimb]]
Chasmosaurines showed little variation in their postcranial skeleton.<ref name="Dino2"/> The skeleton of ''Triceratops'' is markedly robust. Both ''Triceratops'' species possessed a very sturdy build, with strong limbs, short hands with three hooves each, and short feet with four hooves each.<ref name="fujiwara2009">{{Cite journal |last=Fujiwara |first=Shin-Ichi |date=December 12, 2009 |title=A reevaluation of the manus structure in ''Triceratops'' (Ceratopsia: Ceratopsidae) |journal=Journal of Vertebrate Paleontology |volume=29 |issue=4 |pages=1136–1147 |doi=10.1671/039.029.0406 |bibcode=2009JVPal..29.1136F |s2cid=86519018 |issn=0272-4634}}</ref> The [[vertebral column]] consisted of ten neck, twelve back, ten sacral, and about forty-five tail [[vertebra]]e. The front neck vertebrae were fused into a syncervical. Traditionally, this was assumed to have incorporated the first three vertebrae, thus implying that the frontmost [[atlas (anatomy)|atlas]] was very large and sported a neural spine. Later interpretations revived an old hypothesis by [[John Bell Hatcher]] that, at the very front, a vestige of the real atlas can be observed, the syncervical then consisting of four vertebrae. The vertebral count mentioned is adjusted to this view. In ''Triceratops'', the neural spines of the neck are constant in height and don't gradually slope upwards. Another peculiarity is that the neck ribs only begin to lengthen with the ninth cervical vertebra.<ref name="Dino2"/>

The rather short and high vertebrae of the back were, in its middle region, reinforced by ossified tendons running along the tops of the [[neural arch]]es. The straight sacrum was long and adult individuals show a fusion of all sacral vertebrae. In ''Triceratops'' the first four and last two sacrals had transverse processes, connecting the vertebral column to the pelvis, that were fused at their distal ends. Sacrals seven and eight had longer processes, causing the sacrum to have an oval profile in top view. On top of the sacrum, a neural plate was present formed by a fusion of the neural spines of the second through fifth vertebrae. ''Triceratops'' had a large pelvis with a long [[Ilium (bone)|ilium]]. The [[ischium]] was curved downwards. The foot was short with four functional toes. The phalangeal formula of the foot is 2-3-4-5-0.<ref name="Dino2"/>

[[File:Triceratops horridus.png|thumb|right|[[Life restoration]] of ''T. horridus'']]
Although certainly [[quadruped]]al, the posture of horned dinosaurs has long been the subject of some debate. Originally, it was believed that the front legs of the animal had to be [[Terrestrial locomotion#Posture|sprawling]] at a considerable angle from the [[thorax]] in order to better bear the weight of the head.<ref name="Dodhorned">{{Cite book |title=The Horned Dinosaurs |last=Dodson |first=P. |publisher=Princeton University Press |year=1996 |isbn=978-0-691-02882-8 |location=Princeton, New Jersey |url=https://archive.org/details/horneddinosaursn00dods_0 }}</ref> This stance can be seen in paintings by [[Charles R. Knight|Charles Knight]] and [[Rudolph F. Zallinger|Rudolph Zallinger]]. [[Ichnological]] evidence in the form of [[fossil trackway|trackways]] from horned dinosaurs and recent reconstructions of skeletons (both physical and digital) seem to show that ''Triceratops'' and other ceratopsids maintained an upright stance during normal locomotion, with the elbows flexed to behind and slightly bowed out, in an intermediate state between fully upright and fully sprawling, comparable to the modern rhinoceros.<ref name="fujiwara2009"/><ref name="CP01">{{cite journal | last1 = Christiansen | first1 = P. | last2 = Paul | first2 = G.S. | year = 2001 | title = Limb bone scaling, limb proportions, and bone strength in neoceratopsian dinosaurs | url = http://gspauldino.com/GaiaNeoceratopsian.pdf | journal = Gaia | volume = 16 | pages = 13–29 | access-date = October 29, 2012 | archive-date = August 19, 2018 | archive-url = https://web.archive.org/web/20180819045306/http://gspauldino.com/GaiaNeoceratopsian.pdf | url-status = live }}</ref><ref name="thompsonholmes2007">{{cite journal |last1=Thompson |first1=S. |last2=Holmes |first2=R. |year=2007 |title=Forelimb stance and step cycle in ''Chasmosaurus irvinensis'' (Dinosauria: Neoceratopsia) |journal=Palaeontologia Electronica |volume=10 |issue=1 |pages=17 p |url=http://palaeo-electronica.org/2007_1/step/index.html |access-date=November 20, 2010 |archive-date=December 11, 2018 |archive-url=https://web.archive.org/web/20181211003615/https://palaeo-electronica.org/2007_1/step/index.html |url-status=live }}</ref><ref name="regaetal2010">{{Cite book |title=New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium |last1=Rega |first1=E. |last2=Holmes |first2=R. |last3=Tirabasso |first3=A. |publisher=Indiana University Press |year=2010 |isbn=978-0-253-35358-0 |editor-last=Ryan |editor-first=Michael J. |location=Bloomington and Indianapolis |pages=340–354 |chapter=Habitual locomotor behavior inferred from manual pathology in two Late Cretaceous chasmosaurine ceratopsid dinosaurs, ''Chasmosaurus irvinensis'' (CMN 41357) and ''Chasmosaurus belli'' (ROM 843) |editor2-last=Chinnery-Allgeier |editor2-first=Brenda J. |editor3-last=Eberth |editor3-first=David A.}}</ref>

The hands and forearms of ''Triceratops'' retained a fairly primitive structure when compared to other quadrupedal dinosaurs, such as [[thyreophora]]ns and many [[sauropod]]s. In those two groups, the forelimbs of quadrupedal species were usually rotated so that the hands faced forward with palms backward ("pronated") as the animals walked. ''Triceratops'', like other ceratopsians and related quadrupedal [[ornithopod]]s (together forming the [[Cerapoda]]), walked with most of their fingers pointing out and away from the body, the original condition for dinosaurs. This was also retained by bipedal forms, like [[theropod]]s. In ''Triceratops'', the weight of the body was carried by only the first three fingers of the hand, while digits 4 and 5 were vestigial and lacked claws or hooves.<ref name="fujiwara2009"/> The phalangeal formula of the hand is 2-3-4-3-1, meaning that the first or innermost finger of the forelimb has two bones, the next has three, the next has four, etc.<ref>{{Cite book |title=Introduction to the study of dinosaurs |last=Martin |first=Anthony J. |date=2006 |publisher=Blackwell Pub |isbn=978-1405134132 |edition=2nd |location=Malden, MA |oclc=61130756}}</ref>

=== Skin ===

[[File:Ceratopsia skin integument.png|right|thumb|alt=|Skin impressions of various ceratopsians; k is from the flank of ''T. horridus'' specimen HMNS PV.1506]]
Preserved skin from ''Triceratops'' is known. This skin consist of large scales, some of which exceed {{Convert|100|mm|in}} across, which have conical projections rising from their center. A preserved piece of skin from the frill of a specimen is also known, which consists of small polygonal basement scales.<ref>{{Cite journal |last1=Bell |first1=Phil R. |last2=Hendrickx |first2=Christophe |last3=Pittman |first3=Michael |last4=Kaye |first4=Thomas G. |last5=Mayr |first5=Gerald |date=August 12, 2022 |title=The exquisitely preserved integument of Psittacosaurus and the scaly skin of ceratopsian dinosaurs |journal=Communications Biology |language=en |volume=5 |issue=1 |pages=809 |doi=10.1038/s42003-022-03749-3 |issn=2399-3642 |pmc=9374759 |pmid=35962036}}</ref>