Herrerasauridae
From Wikipedia, the free encyclopedia
| Herrerasaurids Fossil range: Late Triassic |
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| Mounted Herrerasaurus skeleton cast, at the Field Museum in Chicago | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Theropoda |
| Family: | Herrerasauridae Benedetto, 1973 |
| Genera | |
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Herrerasaurids are among the oldest known dinosaurs, appearing in the fossil record about 228 million years ago (mid-Triassic). They became extinct by the end of the Triassic period. Herrerasaurids were small-sized carnivorous theropods[1] or basal saurischians.[2][3] The best known representatives of this group are from South America (Brazil, Argentina), where they were first discovered in the 1960s. A nearly complete skeleton of Herrerasaurus ischigulastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete herrerasaurids have been found in North America, and they may have inhabited other continents as well.
Herrerasaurid anatomy is unusual and specialized, and they are not considered to be ancestral to any later dinosaur group. They often present a mixture of very primitive and derived traits. The acetabulum is only partly open, and there are only two sacral vertebrae, the lowest number among dinosaurs. The pubic bone has a derived structure, being rotated somewhat posteriorly and folded to create a superficially tetanuran-like terminal expansion, especially prominent in H. ischigulastensis. The hand is primitive in having five metacarpals and the third finger longer than the second, but clearly theropod in having only three long fingers, with curved claws. Herrerasaurids also have a hinged mandible like all theropods
[edit] Taxonomy
- Order Saurischia
- ?Suborder Theropoda
- Family Herrerasauridae
- ?Suborder Theropoda
[edit] References
- ^ Nesbitt, S. J., Smith, N. D., Irmis, R. B., Turner, A. H., Downs, A., and M. A. Norell. (2009). "A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs." Science 326:1530-1533.
- ^ Langer, Max C. (2004). "Basal Saurischia". in Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 25–46. ISBN 0-520-24209-2.
- ^ Langer, M.C; and Benton, M.J. (2006). "Early dinosaurs: a phylogenetic study". Journal of Systematic Palaeontology 4 (4): 309–358. doi:.
