Temporal range: Upper Triassic
Eoraptor was a small, lightly-built dinosaur that walked on two long legs. It was about 3 feet long (1 m); it had light, hollow bones, a long head with dozens of small, sharp teeth, and five fingers on its grasping hands (two of the fingers on each hand were very small).
The fossil was found in the Ischigualasto Formation in the Argentine. This contains some of the oldest known dinosaur remains. They are of top quality, number and importance. It is the only place in the world where nearly all of the Triassic is represented in an undisturbed sequence of strata. What is now badlands was then a volcanically active floodplain dominated by rivers, with a strongly seasonal rainfall.
Rhynchosaurs and cynodonts are by far the most common among the tetrapod fossils in the park. Dinosaurs make up only 6% of the findings, but these include early samples of the two major lineages of dinosaurs (ornithischians and saurischians). The carnivorous Herrerasaurus is the most numerous of these dinosaur fossils.
Teeth[change | edit source]
The teeth of Eoraptor are of two types. There are serrated, recurved teeth in the maxillae (upper jaws), like the teeth of theropods, and leaf-shaped teeth in the dentary (lower jaw), like the teeth of basal sauropodomorphs.
References[change | edit source]
- Apaldetti C et al 2011. A new basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina. PLoS ONE 6 (11): e26964. doi:10.1371/journal.pone.
- Alcober Oscar A. & Martinez, Ricardo N. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63 (63): 55–81. doi:10.3897/zookeys.63.550. PMC 3088398. PMID 21594020. 
- Rogers R.R. et al 1993. The Ischigualasto tetrapod assemblage (late Triassic, Argentina) and 40Ar/39Ar dating of dinosaur origins. Science, 260, 794-797.
- Sereno P.C. et al 1993. Primitive dinosaur skeleton form Argentina and the early evolution of the Dinosauria. Nature 361, 64-66.