Pentaceratops

*Pentaceratops sternbergi*

* Timothy Bradley Artwork
* Robert F Walters Artwork

***Pentaceratops***, meaning "five horned face", was an ornischian (bird-hipped) dinosaur, and was part of the family Ceratopsia. In the brief time that it roamed the earth, *Pentaceratops*, like the other members of its brood, were highly successful, and for a time, the earth was overrun by millions of these bulky tank-like creatures. *Pentaceratops*, despite its name, only had three true horns. the other two were no more than elongated cheekbones, a feature which was a common characteristic of many other ceratopsians. *Pentaceratops*, as with all horned dinosaurs, had a curved, toothless beak which it used to nip leaves of plants. Also one of *Pentaceratops*, and indeed, all of its relative's, defining features was its large ornate defensive crest-shield, which was used both to protect from and deter predators, and to use in courtship and mating rituals.

The frill-face of the Pentaceratops was less thick, and much more weaker than the regular frill of the most common ceratopsid, Triceratops. If a tyrannosaur such as Gorgosaurus or Albertosaurus were to attack a Pentaceratops, it would've fallen prey, as its frill wouldn't have stopped its devastating bite. However, the frill was stretched, huge, and probably was a vibrant color or was used in some sort of way to deter the predator, by intimidation. The skull of a Pentaceratops is the largest skull of any land-based animal to have ever lived, almost as large as a 4th grader.

## Discovery and Species

The first exemplars were collected by Charles Hazelius Sternberg in the San Juan Basin in New Mexico. In 1921, Sternberg worked in commission of the Swedish Uppsala University and recovered at the Meyers Creek near the Kimbetoh Wash, in a layer of the Kirtland Formation, a skull and a rump, specimens PMU R.200 and PMU R.286 that he sent to paleontologist Carl Wiman. In 1922 Sternberg decided to work on his own account and discovered north of Tsaya Trading Post, in the Fossil Forest of San Juan County, a complete skeleton that he sold to the American Museum of Natural History. The museum then sent out a team headed by Charles Mook and Peter Kaisen to assist Sternberg in securing this specimen; subsequent digging by Sternberg in 1923 brought the total of AMNH specimens at four. The rump of the main specimen was discarded because it had insufficient value as a display.

The species was named and described by Henry Fairfield Osborn in 1923, as *Pentaceratops sternbergii*. The generic name means "five-horned face", derived from the Greek penta (πέντα, meaning five), keras (κέρας, horn) and -ops (ὤψ, face), in reference to its two long epijugal bones, spikes which protrude out sidewards from under its eyes, in addition to the three more obvious horns as with *Triceratops*. Osborn obligingly gave it the specific name *sternbergii* honoring its discoverer as a veteran fossil hunter. The name had been suggested to Osborn by William Diller Matthew; the specific epithet served as a consolation to the almost bankrupt Sternberg whose 1923 fossils were initially not acquired by the museum that had to use its 1923/1924 budget to process the finds of the great Asian expeditions by Roy Chapman Andrews.

The holotype was the skull discovered by Sternberg in 1922, specimen AMNH 6325. It was found in a layer of the Fruitland Formation, dating from the Campanian, about seventy-five million years old. The other three AMNH specimens were AMNH 1624, a smaller skull; AMNH 1622, a pair of brow horns; and AMNH 1625, a piece of skull frill.

In 1930, Wiman named a second species of *Pentaceratops*: *Pentaceratops fenestratus*. It was based on Sternberg's 1921 specimens and the specific name referred to a hole in the left squamosal. This was later considered to be the same species as, and thus a junior synonym of, *Pentaceratops sternbergii*, the hole being the likely effect of an injury.

In 1929 George Fryer Sternberg discovered specimen USNM V12002, a right squamosal. *Pentaceratops* proved to be a quite common fossil in the Fruitland and Kirtland formations. It has even been used as guide fossil: the appearance of *Pentaceratops sternbergii* in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian.[1] Subsequent finds include specimens MNA Pl. 1668, MNA Pl. 1747, NMMNH P-27468 and USNM 2416, partial skeletons with skull; YPM 1229, a skeleton lacking the skull; UALP 13342 and UKVP 16100, skulls; UNM B-1701, USNM 12741, USNM 12743, USNM 8604, SMP VP-1596, SMP VP-1488, SMP VP-1500 and SMP VP-1712, fragmentary skulls. Apart from the San Juan Basin finds, a juvenile specimen of *Pentaceratops*, SDMNH 43470, has been reported from the Williams Fork Formation of Colorado in 2006.

Sometimes the identification of a specimen as *Pentaceratops* has proven to be highly contentious. In 1998 Thomas Lehman described OMNH 10165, a very large skull and its associated skeleton found in New Mexico in 1941, and presently on display at the Sam Noble Oklahoma Museum of Natural History, as being the largest *Pentaceratops* exemplar known, with the distinction of having produced the largest known skull of any land vertebrate. However, in 2011, the skeleton was renamed as a separate genus: *Titanoceratops*.

## Description

*Pentaceratops* is a large ceratopsid. Its known maximum size is dependent on the identity of specimen OMNH 10165. This specimen has a reconstructed length of 6.8 meters, a reconstructed skull length of 3.22 metres and a weight estimated by Lehman at 9877 kilograms. The other specimens are smaller. Gregory S. Paul in 2010 estimated the body length at 6.4 meters and the weight at 4.7 tonnes. Lehman calculated a composite maximal skull length for the smaller specimens of about 2.7 meters. Dodson estimated the body length at six meters, the skull length of AMNH 1624 at 2.3 meters. 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.

The torso of *Pentaceratops* is tall and wide. The rear dorsal vertebrae bear long spines from which perhaps ligaments ran to the front, to balance the high frill. The prepubis is long. The ischium is long and strongly curves forward. With the smaller specimens the thigh bone bows outwards.

## JPInstitute.com Description

Pentaceratops was a member of the family of dinosaurs known as ceratopsian, of which Triceratops was also a member. It was a fairly large plant-eater that had a long neck frill with large holes in the bone. These holes would have been covered with skin. It had long horns over its eyes and a smaller horn over its nose.

Pentaceratops gets its name of "Five Horned Face" not because it had five horns, but because it had longer epijugals - the spike-like cheek projections that are present on all ceratopsians to some degree. This dinosaur had a very large frill and to date, no complete frill has been found. These large frills may have been used as a display against frontal threats. There is some discussion that Chasmosaurus and Pentaceratops belong in the same genus.

## Appearance in other media

### *Jurassic Park*

* Pentaceratops appeared in the video game Jurassic World: Evolution.

## Links

http://web.archive.org/web/20040214162932/http://www.jpinstitute.com/dinopedia/dinocards/dc\_penta.html