Harpymimus
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| Harpymimus oklandnikovi Barsbold & Perle, 1984 |
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 etymology of Harpymimus involves 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. Other dinosaurs collected from the Shinekhudug Formation at Dundgov include the ceratopsian Psittacosaurus mongoliensis and the ornithopod Altirhinus kurzanovi.
[edit] Diagnosis and Morphology
Kobayashi & Barsbold (2005, p. 100) diagnose Harpymimus as follows: "Eleven dentary teeth, which are anterior in position; transition between anterior and posterior caudal vertebrae at eighteenth caudal; traiangular-shaped depression of dorsal surface of supragelnoid buttress of scapula; low ridge dorsal to depression along posterior edge of scapular blade; small but deep collateral ligament fossa on lateral condyle of metacarpal III." The holotype skull of Harpymimus is virtually complete, but badly crushed laterally, obscuring some anatomical detail. There is evidence of a rhampotheca (beak) covering the upper jaw which, in concert with the dentary teeth, was likely employed for grasping and holding onto prey. It's general appearance was much like that of later ornithomimosaurs (long-necked, long arms with sharp grasping claws, and long legs). The dentition of Harpymimus differs from that of another basal ornithomimosaur, Pelecanimimus polyodon, in that teeth are restricted to the dentary and number between ten and eleven. Pelecanimimus possessed seventy-five dentary teeth, as well as an additional 145 teeth in the maxillae and premaxillae. The small teeth of Harpymimus were probably used only for grabbing and holding prey, unlike those of many other non-avian theropods, which were adapted to cutting or piercing (Kobayashi & Barsbold (2005, p. 119). Of all the known ornithomimosaurs, only Harymimus and Pelecanimimus retain teeth, a trait which is plesiomorphic ("primitive") for the clade Orithomimosauria. The anteroposterior 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).
[edit] Phylogeny
Kobayashi & Barsbold (2005, pp. 118-123) have conducted a detailed cladistic analysis of this taxon and have determined that Harpymimus is basal to the clade of Garudimimus brevipes plus Ornithomimidae, yet is more derived than Pelecanimimus polyodon. The conclusions of this analysis support the model that ornithomimosaurs originated in either eastern Asia or in Europe prior to the Barremian (130-125 million years ago), the migrated to North America during or at some time before the Late Cretaceous.
[edit] References
- Barsbold, R. et Perle, A. 1984. [On first new find of a primitive orithomimosaur from the Cretaceous of the MPR]. Paleontologicheskii zhurnal 2: 121-123.
- Kobayashi, Y. et Barsbold, R. 2005. Anatomy of Harpymimus okladnikovi Barsbold and Perle 1984 (Dinosauria; Theropoda) of Mongolia. in The Carnivorous Dinosaurs ed. Carpenter, K. 2005. Indiana University Press: pp. 97-126.
