Pentaceratops

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Pentaceratops
Temporal range: Late Cretaceous, 76–73Ma
Pentaceratops sternbergii holotype AMNH6325.jpg
Type skull of Pentaceratops sternbergii, AMNH 6325
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Ceratopsidae
Subfamily: Chasmosaurinae
Genus: Pentaceratops
Osborn, 1923
Species: † P. sternbergii
Binomial name
Pentaceratops sternbergii
Osborn, 1923
Synonyms

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[1] in the San Juan Basin in New Mexico. Other dinosaurs which shared its habitat include Parasaurolophus cyrtocristatus, the pachycephalosaur Sphaerotholus, the armored dinosaur Nodocephalosaurus and the tyrannosauroid Bistahieversor. About a dozen skulls and skeletons have been uncovered, so that most bones are known. Of one very large specimen it is contested whether it belongs to Pentaceratops or represents a genus of its own: Titanoceratops. However, some subsequent researchers have considered Titanoceratops merely a large individual of P. sternbergii.[2]

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.

Discoveries and species[edit]

Skeletal restoration of a large specimen sometimes classified as Titanoceratops

The first exemplars were collected by Charles Hazelius Sternberg in the San Juan Basin in New Mexico. Sternberg worked in commission for the Swedish Uppsala University . In 1921 he recovered a skull and a rump, specimens PMU R.200 and PMU R.286, at the Meyers Creek near the Kimbetoh Wash, in a layer of the Kirtland Formation, he sent the fossils to paleontologist Carl Wiman. In 1922 Sternberg decided to work on his own account and north of Tsaya Trading Post, in the Fossil Forest of San Juan County, he discovered a complete skeleton , which 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 to four. The rump of the main specimen was discarded by the museum 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),[3] 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.[4] 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.[5]

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.[4]

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.[6] This was later considered to be the same species as Pentaceratops sternbergii and thus a junior synonym, the hole being the likely effect of an injury.

In 1929 Steinberg's son, 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 a 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.[7]

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.[8][9] However, in 2011, the skeleton was renamed as a separate genus: Titanoceratops.[10]

Description[edit]

Life restoration of a large specimen sometimes classified as Titanoceratops

Pentaceratops is a large ceratopid. 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.[8] 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.[11] 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.[6]

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.[12] Within the notch the first epiparietals point forwards. The very thick jugal and the squamosal do not touch each other, a possible autapomorphy.[10]

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.[11]

Classification[edit]

Osborn originally assigned Pentaceratops to the Ceratopsia. Within this group Pentaceratops belonged to the Ceratopsinae or Chasmosaurinae. It appears to be most closely related to Utahceratops. Their clade was perhaps more derived than the earlier genus Chasmosaurus but more basal than Anchiceratops, the latter representing a line of which Triceratops was a member, which lived a few million years later, right at the end of the Cretaceous period, when all ceratopsians died out.

The following cladogram shows the phylogeny of Pentaceratops according to a study by Scott Sampson et al in 2010.[13]

Ceratopidae 

Centrosaurinae


 Chasmosaurinae 

Chasmosaurus




Mojoceratops




Agujaceratops





Utahceratops



Pentaceratops





Coahuilaceratops





Kosmoceratops



Vagaceratops





Anchiceratops




Arrhinoceratops




Ojoceratops



Eotriceratops




Torosaurus




Nedoceratops



Triceratops














Diet[edit]

Restoration

Pentaceratops, like all ceratopsians, was an herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the branches which then were shredded, leaves, needles and all, by the tooth batteries, providing a self-sharpening continuous cutting edge in both upper an lower jaws. Ultimately the plant material was digested by the large gut.

See also[edit]

Footnotes[edit]

  1. ^ a b c Sullivan and Lucas (2006).
  2. ^ Wick, S. L.; Lehman, T. M. (2013). "A new ceratopsian dinosaur from the Javelina Formation (Maastrichtian) of West Texas and implications for chasmosaurine phylogeny". Naturwissenschaften. in press (7): 667. Bibcode:2013NW....100..667W. doi:10.1007/s00114-013-1063-0.  edit
  3. ^ a b Liddell, et al. (1980). pp. 373, 542-43, 804.
  4. ^ a b H.F. Osborn, 1923, "A new genus and species of Ceratopsia from New Mexico, Pentaceratops sternbergii, American Museum Novitates 93: 1-3
  5. ^ Sullivan, R.M. and S.G. Lucas, 2011, "Charles Hazelius Sternberg and his San Juan Basin Cretaceous dinosaur collections: Correspondence and photographs (1920-1925)", New Mexico Museum of Natural History and Science Bulletin 53: 429-471
  6. ^ a b C. Wiman, 1930, "Über Ceratopsia aus der Oberen Kreide in New Mexico", Nova Acta Regiae Societatis Scientiarum Upsaliensis, Series 4 7(2): 1-19
  7. ^ a b Lucas, et al. (2006).
  8. ^ a b Lehman, T.M., 1998, "A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico: Journal of Paleontology, 72(5): 894-906
  9. ^ a b Delayed Debut for Jumbo Dino Skull
  10. ^ a b c Longrich (2011).
  11. ^ a b Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 272
  12. ^ Rowe, T., Colbert, E.H. and Nations, J.D., 1981, "The occurrence of Pentaceratops with a description of its frill", In: Lucas, S.G., Rigby, J.K. and Kues, B.S. (eds.) Advances in San Juan Basin Paleontology, University of New Mexico Press, Alburquerque p. 29-48
  13. ^ Scott D. Sampson, Mark A. Loewen, Andrew A. Farke, Eric M. Roberts, Catherine A. Forster, Joshua A. Smith, and Alan L. Titus (2010). "New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism". In Stepanova, Anna. PLoS ONE 5 (9): e12292. doi:10.1371/journal.pone.0012292. PMC 2929175. PMID 20877459. 

References[edit]

External links[edit]