Harpymimus
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| Harpymimus Fossil range: Early Cretaceous |
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Harpymimus was a basal ornithomimosaur from the Early Cretaceous Period of what is now Mongolia. Unlike later, more derived ornithomimosaurs, Harpymimus still possessed teeth, although they appear to have been restricted to the lower jaw (dentary). The holotype specimen (IGM 100/29, Mongolian Academy of Sciences, Ulan Bator, Mongolia) consists of an almost complete skeleton, lacking portions of the pectoral girdle, pelvic girles, and hindlimbs. It was recovered at Dundgovi Aimag (Eastern Gobi Province), from an exposure of the Shinekhudug Formation (Shinekhudukskaya Svita; Hauterivian to Barremian). The name Harpymimus is a reference to the fearsome Harpy of Greek mythology (Greek harpyiai = "Harpies" + Greek mimos = "mimic"). Only a single species is known for this genus, H. oklandnikovi.[1] Other dinosaurs collected from the Shinekhudug Formation at Dundgov include the ceratopsian Psittacosaurus mongoliensis and the ornithopod Altirhinus kurzanovi.
[edit] Description
In a 2005 re-evaluation, Kobayashi and Rinchen Barsbold diagnosed Harpymimus based on a number of anatomical characteristics, including eleven teeth in the front of the lower jaw (dentary), the transition between anterior and posterior tail vertebrae at the eighteenth caudal, traiangular-shaped depression of dorsal surface of the shoulder blade (scapula), a low ridge above a distinctive depression along back edge of the shoulder blade, and a small but deep collateral ligament fossa on the lateral condyle of metacarpal III (a hand bone).
The skull of the type specimen of Harpymimus is virtually complete, but badly crushed, obscuring some anatomical detail. There is evidence of a beak covering the upper jaw which, in concert with the dentary teeth, was likely employed for grasping and holding onto prey. Its general appearance was much like that of later ornithomimosaurs (long-necked, long arms with sharp grasping claws, and long legs). The teeth of Harpymimus differ from those of another basal ornithomimosaur, Pelecanimimus polyodon, in that they are restricted to the dentary and number between ten and eleven. Pelecanimimus possessed 75 dentary teeth, as well as an additional 145 teeth in the upper jaw (maxillae and premaxillae). The small teeth of Harpymimus were probably used only for grabbing and holding prey, unlike those of many other theropods, which were adapted to cutting or piercing. Of all the known ornithomimosaurs, only Harpymimus and Pelecanimimus retained teeth, a trait which is primitive (plesiomorphic) for the clade Orithomimosauria.
The length of the skull is approximaley 262 mm, more than twice its approximate height and less than half the length of the neck (approximately 600 mm).[2]
[edit] Phylogeny
In their 2005 paper, Kobayashi and Barsbold also conducted a detailed cladistic analysis of Harpymimus and determined that Harpymimus is basal to the clade of Garudimimus brevipes plus Ornithomimidae, yet is more derived than Pelecanimimus polyodon. According to these researchers, the conclusions of the analysis supported the model that ornithomimosaurs originated in either eastern Asia or in Europe prior to the Barremian stage of the Early Cretaceous (130-125 million years ago), then migrated to North America during or at some time before the Late Cretaceous.[2]
[edit] References
- ^ Barsbold, R. and Perle, A. (1984). [On first new find of a primitive orithomimosaur from the Cretaceous of the MPR]. Paleontologicheskii zhurnal, 2: 121-123.
- ^ a b Kobayashi, Y. and Barsbold, R. (2005). "Anatomy of Harpymimus okladnikovi Barsbold and Perle 1984 (Dinosauria; Theropoda) of Mongolia." In Carpenter, K. (ed.) The Carnivorous Dinosaurs. Indiana University Press: 97-126.
