Editing Triceratops (section)

===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>