Parksosaurus
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Extinct (fossil)
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| Parksosaurus warreni C. M. Sternberg, 1937 |
Parksosaurus ("William Parks's lizard") was a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull. It is one of the few described non-hadrosaurid ornithopods from the end of the Cretaceous in North America.
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[edit] History and Taxonomy
Paleontologist William Parks described skeleton ROM 804 in 1926 as Thescelosaurus warreni, which had been discovered in what was then called the Edmonton Formation near Rumsey Ferry on the Red Deer River. When found, it consisted of a partial skull (missing the beak region), most of the left pectoral girdle (including a suprascapula, a bone more commonly found in lizards, but which is believed to have been present in cartilage form in some ornithopods due to the roughened ends of their scapulae {see for example Gilmore (1915) on Thescelosaurus[1]}), the left arm except the hand, ribs and sternal elements, a damaged left pelvis, right ischium, the left leg except for some toe bones, articulated vertebrae from the back, hip, and tail, and a number of ossified tendons (which sheathed the end of the tail).[2]
The body of the animal had fallen on its left side, and most of the right side had been destroyed before burial; in addition, the head had been separated from the body, and the neck lost. Parks differentiated the new species from T. neglectus by leg proportions; T. warreni had a longer tibia than femur, and longer toes.[2]
Charles M. Sternberg, upon the discovery of the specimen he named Thescelosaurus edmontonensis, revisited T. warreni and found that it warranted its own genus (it was named in an abstract, which is not typical, but the specimen had already been described thoroughly).[3] In 1940, he made a more thorough comparison and found a number of differences between the two genera throughout the body. He assigned Parksosaurus to the Hypsilophodontinae with Hypsilophodon and Dysalotosaurus, and Thescelosaurus to the Thescelosaurinae.[4]
The genus attracted very little attention until Peter Galton began his revision of hypsilophodonts in the 1970s. Parksosaurus received a redescription in 1973, wherein it was considered to be related to a Hypsilophodon\Laosaurus\L. minimus lineage.[5] After this, it once again returned to obscurity, despite being known from decent remains. Recent reviews have dealt with it without much comment,[6][7] although Norman et al. (2004), in the framework of a paraphyletic Hypsilophodontidae, found it to be the sister taxon to Thescelosaurus.[7] Like Thescelosaurus, it has a relatively robust hindlimb, and an elongate skull without as much arching compared to other hypsilophodonts.[7] However, basal ornithopod phylogeny is poorly known at this point, albeit under study.
[edit] Paleobiology
Explicit estimates of the entire size of the animal have not been done, but Parks found the hindlimb of his T. warreni to be about the same length as that of Thescelosaurus neglectus (930 mm [3.05 feet] versus 955 mm [3.13 ft]).[2] Thus, the animal would have been comparable to the better-known Thescelosaurus in linear dimensions, despite proportional differences (around 1 m [3.28 feet] tall at the hips, 2-2.5 m [6.56-8.2 feet] long; estimated after[2]). The proportional differences probably would have made it lighter, though, as less mass was concentrated near the femur.
In life, Parksosaurus, as a hypsilophodont, would have been a small, swift bipedal herbivore. It would have had a moderately long neck and small head with a horny beak, short but strong forelimbs, and long powerful hindlimbs.[7]
[edit] Miscellaneous
George Olshevsky emended the name to P. warrenae in 1992,[8] because the species name honors a woman (Mrs. H. D. Warren), but outside of Internet sites, this has not been generally used.[7]
[edit] References
- ^ Gilmore, C.W. (1915). Osteology of Thescelosaurus, an orthopodus dinosaur from the Lance Formation of Wyoming. Proceedings of the U.S. National Museum 49(2127):591-616.
- ^ a b c d Parks, W.A. (1926). Thescelosaurus warreni, a new species of orthopodous dinosaur from the Edmonton Formation of Alberta. University of Toronto Studies (Geological Series) 21:1-42.
- ^ Sternberg, C.M. (1937). Classification of Thescelosaurus, with a description of a new species. Geological Society of America Proceedings for 1936:365.
- ^ Sternberg, C.M. (1940). Thescelosaurus edmontonensis, n. sp., and classification of the Hypsilophodontidae. Journal of Paleontology 14(5):481-494.
- ^ Galton, P.M. (1973). Redescription of the skull and mandible of Parksosaurus from the Late Cretaceous with comments on the family Hypsilophodontidae (Ornithischia). Life Sciences Contribution, Royal Ontario Museum 89:1-21.
- ^ Sues, H.-D., and Norman, D.B. (1990). Hypsilophodontidae, Tenontosaurus, Dryosauridae. In: Weishampel, D.B., Osmólska, H., and Dodson, P. (eds.). The Dinosauria. University of California Press:Berkeley, 498-509. ISBN 0-520-06727-4
- ^ a b c d e Norman, D.B., Sues, H.D., Witmer, L.M., and Coria, R.A. (2004). Basal Ornithopoda. In: Weishampel, D.B., Osmólska, H., and Dodson, P. (eds.). The Dinosauria (second edition). University of California Press:Berkeley, 393-412. ISBN 0-520-24209-2
- ^ Olshevsky, G. (1992). A revision of the parainfraclass Archosauria Cope 1869, excluding the advanced Crocodylia. Mesozoic Meanderings, 268 p.
