Eoraptor lunensis is from the late Triassic of Argentina. One of the earliest known dinosaurs and a contemporary of Herrerasaurus, its already bipedal stance and short, specialized forelimbs suggest an affinity with theropod dinosaurs. Eoraptor lends support to the hypothesis that dinosaurs diverged rapidly and at small body sizes from a common ancestor, and that the main herbivorous and carnivorous lineages were already present by the Middle Carnian. Information about its internal cranial anatomy derived from CT scanning should shed additional light on the origin and early evolution of dinosaurs.

This specimen, the skull of the holotype, was collected from the Upper Triassic Ischigualasto Formation (232 Ma), Valley of the Moon, northwestern Argentina. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning courtesy of Dr. Oscar Alcober of the Universidad Nacional de San Juan. Funding for this scan was provided by Dr. Timothy Rowe of The University of Texas at Austin.

The specimen was scanned by Richard Ketcham and Cambria Denison on 30 October 1997 along the coronal axis for a total of 346 slices, each slice 0.25 mm thick, with an interslice spacing of 0.2 mm (for a slice overlap of 0.05 mm).

Sereno, P. C. 1999. The evolution of dinosaurs. Science 284:2137-2147.

Sereno, P. C., C. A. Forster, R. R. Rogers, and M. M. Monetta. 1993. Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria. Nature 361:64-66.

Links

Learn more about Eoraptor on the Texas Memorial Museum of Science and History website

Learn more about the Ischigualasto Formation and its fauna at Eldinosaurio.com

None available.