Pentaceratops

Name: Pentaceratops (Five horn face).
Phonetic: Pen-tah-seh-rah-tops.
Named By: Henry Fairfield Osborn - 1923.
Classification: Chordata, Reptilia, Dinosauria, Ornithischia, Ceratopsia, Ceratopsidae, Chasmosaurinae.
Species: P. sternbergii (type).
Diet: Herbivore.
Size: Average seems to be around 6 meters long, though several specimens have been estimated at around 6.5 to 7 meters long.
Known locations: USA, New Mexico, Colorado.
Time period: Campanian of the Cretaceous.
Fossil representation: Many known specimens.

       Pentaceratops is one of the better known ceratopsian dinosaurs, yet some people still mistakingly think that it have five horns, based upon the literal translation of its name. In actual fact the nasal and brow (over the eye) horns make up number one to three, with horns four and five actually being the sharply pointed cheek bones. Whereas ceratopsian dinosaurs are noted for having large cheek bones (jugals) they are more often rounded rather than pointed.
       Pentaceratops is a chasmosaurine ceratopsian (the group based upon the description of Chasmosaurus) and as such has a proportianately larger neck frill than other ceratopsian groups. In fact Pentaceratops is known for having one of the largest neck frills of this group, and is part of the reason why Pentaceratops is regarded as having the largest skull for any land vertebrate. This large frill size was possible due to the presence of enlarged skull fenestra that made the frill resemble a frame rather than a solid piece of bone. This also suggests that the frill served a display rather than a defensive purpose as the gaps in the frill would have been filled only by a thin growth of skin and tissue.
       With an upper size approaching seven meters in length, Pentaceratops had few predators to worry about when fully grown. However one potential predator may have been the short snouted tyrannosaurid Bistahieversor which was also active in the same area and time as Pentaceratops. Still, current fossil evidence suggests that Bistahieversor was only slightly longer than a fully grown Pentaceratops, and it may have been the young, old, and infirm individuals that may had reason to fear attack from predators.
       Some sources continue to state that Pentaceratops could grow up to nine meters long, and while future fossil evidence may confirm this, the nine meter size estimate is based upon Pentaceratops fossil specimens that have since been found to represent a new genus which has since been named Titanoceratops. Related and similar ceratopsian dinosaurs include the aforementioned Chasmosaurus as well as Anchiceratops.

Further reading
- A new genus and species of Ceratopsia from New Mexico, Pentaceratops sternbergii - American Museum Novitates 93: 1-3 - Henry Fairfield Osborn - 1923.
- The occurrence of Pentaceratops with a description of its frill - T. Rowe, E. H. Colbert & J. D. Nations - 1981 - In: Advances in San Juan Basin Paleontology, University of New Mexico Press, Alburquerque p. 29-48 - S. G. Lucas, J. K. Rigby & B. S. Kues (eds.).
- A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico - Journal of Paleontology 72 (5): 894–906 - T. M. Lehman - 1998.
- Re-evaluation of Pentaceratops and Chasmosaurus (Ornithischia: Ceratopsidae) in the Upper Cretaceous of the Western Interior - S. G. Lucas, R. M. Sullivan & A. P. Hunt - 2006 - In Late Cretaceous Vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35:367-370 - S. G. Lucas and R. M. Sullivan (eds).
- The horned dinosaurs Pentaceratops and Kosmoceratops from the upper Campanian of Alberta and implications for dinosaur biogeography. - Cretaceous Research, 51: 292-308. - N. Longrich - 2014.

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