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Triceratops prorsus is a species of Triceratops, alongside T. horridus. It lived at the same time and place as its cousin.

Classification

The T. prorsus was classified as its own species alongside:

  • T. albertensis (Charles Mortram Sternberg, 1949)
  • T. alticornis (Othniel Charles Marsh, 1887 [originally Bison])
  • T. brevicornus (Hatcher, 1905) (=T. prorsus)
  • T. calicornis (Marsh, 1898) (=T. horridus)
  • T. elatus (Marsh, 1891) (=T. horridus)
  • T. eurycephalus (Erich Maren Schlaikjer, 1935)
  • T. flabellatus (Marsh, 1889) (=T. horridus)
  • T. galeus (Marsh, 1889)
  • T. hatcheri (Lull, 1907)
  • T. ingens (R. S. Lull, 1915)
  • T. maximus (Barnum Brown, 1933)
  • T. mortuarius (Edward Drinker CopeCope, 1874) (nomen dubium; originally Polyonax mortuarius)
  • T. obtusus (Marsh, 1898) (=T. horridus)
  • T. serratus (Marsh, 1890) (=T. horridus)
  • T. sulcatus (Marsh, 1890)
  • T. sylvestris (Cope, 1872) (nomen dubium; originally Agathaumas sylvestris)

All of these species were named, but today only T. horridus and T. prorsus remain as valid species. In 1986, Ostrom and Wellnhofer published a paper in which they proposed that there was only one species, Triceratops horridus.[1] Part of their rationale was that generally there are only one or two species of any large animal in a region (modern examples being the elephant and the giraffe in modern Africa). To their findings, Lehman added the old Lull-Sternberg lineages combined with maturity and sexual dimorphism, suggesting that the T. horridus-T. prorsus-T. brevicornus lineage was composed of females, the T.calicornis-T.elatus lineage was made up of males, and the T. obtusus-T. hatcheri lineage was of pathologic old males.[2] His reasoning was that males had taller, more erect horns and larger skulls, and females had smaller skulls with shorter, forward-facing horns.

These findings were contested a few years later by Catherine Forster, who reanalyzed Triceratops material more comprehensively and concluded that the remains fell into two species, T. horridus and T. prorsus, although the distinctive skull of T. ("Nedoceratops") hatcheri differed enough to warrant a separate genus.[3] She found that T. horridus and several other species belonged together, and T. prorsus and T. brevicornus stood alone, and since there were many more specimens in the first group, she suggested that this meant the two groups were two species. It is still possible to interpret the differences as representing a single species with sexual dimorphism.[4][5]

In 2009, John Scannella and Denver Fowler supported the separation of T. prorsus and T. horridus, and noted that the two species are also separated stratigraphically within the Hell Creek Formation, indicating that they did not live together at the same time.[6]

Triceratops prorsus in The Land Before Time

A Triceratops prorsus appears as a spotted Threehorn in the TV series episode The Hidden Canyon as one of the members of the Great Valley defense, helping to fight off Screech and Thud. He looks a bit different from other Triceratops that appear in the LBT universe. He and Daddy Topps chased them away once they were defeated. A Triceratops prorsus also appears at the Rock Circle after the attack.

References

  1. Ostrom, J. H.; Wellnhofer, P. (1986). "The Munich specimen of Triceratops with a revision of the genus". Zitteliana 14: 111–158. 
  2. Cite error: Invalid <ref> tag; no text was provided for refs named TML90
  3. Forster, C.A. (1996). "Species resolution in Triceratops: cladistic and morphometric approaches". Journal of Vertebrate Paleontology 16 (2): 259–270. doi:10.1080/02724634.1996.10011313. 
  4. Cite error: Invalid <ref> tag; no text was provided for refs named Dodhorned
  5. 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. 
  6. Scannella, J.B. and Fowler, D.W. (2009). "Anagenesis in Triceratops: evidence from a newly resolved stratigraphic framework for the Hell Creek Formation." Pp. 148–149 in 9th North American Paleontological Convention Abstracts. Cincinnati Museum Center Scientific Contributions 3.

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