Pentaceratops sternbergii
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Pentaceratops Temporal range: Late Cretaceous, 75.79–73 Ma |
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| Holotype skull of P. sternbergii, AMNH 6325 | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Family: | †Ceratopsidae |
| Subfamily: | †Chasmosaurinae |
| Genus: |
†Pentaceratops Osborn, 1923 |
| Type species | |
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Pentaceratops sternbergii Osborn, 1923 |
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| Species | |
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Pentaceratops ("five-horned face") is a genus of herbivorous ceratopsid dinosaur from the late Cretaceous Period of what is now North America.
Pentaceratops fossils were first discovered in 1921. The genus was named in 1923 when its type species Pentaceratops sternbergii was described. Pentaceratops lived around 76–73 million years ago, its remains having been mostly found in the Kirtland Formation in the San Juan Basin in New Mexico. About a dozen skulls and skeletons have been uncovered, so that most bones are known. One exceptionally large specimen later became its own genus, Titanoceratops, due to its more derived morphology closer to Triceratops and lack of unique characters shared with Pentaceratops proper, although the author that originally assigned it to Pentaceratops has decided to ignore this in subsequent publications.
Pentaceratops was about six meters (twenty feet) long, and has been estimated to have weighed around five tonnes. It had a short nose horn, two long brow horns, and long horns on the jugal bones. Its skull had a very long frill with triangular hornlets on the edge.
Pentaceratops is a large ceratopsid, Dodson estimated the body length at six meters, the skull length of AMNH 1624 at 2.3 meters while PMU R.200 has a length of 216 centimeters. The nose horn of Pentaceratops is small and pointing upwards and backwards. The brow horns are very long and curving strongly forwards. The somewhat upward tilted frill of Pentaceratops is considerably longer than that of Triceratops, with two large holes (parietal fenestrae) in it. It is rectangular, adorned by large triangular osteoderms: up to twelve episquamosals at the squamosal and three epiparietals at the parietal bone. These are largest at the rear corners of the frill, that are separated by a large U-shaped notch at the midline, a feature not recognized until 1981 when specimen UKVP 16100 was described. Within the notch the first epiparietals point forwards. The very thick jugal and the squamosal do not touch each other, a possible autapomorphy.
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