9304896 Sereno By the end of the Triassic Period, a major transition in terrestrial vertebrate communities had occurred with the replacement of therapsid-dominated faunas by dinosaur-dominated faunas that would persist until the end of the Mesozoic. Fossiliferous deposits in northwestern Argentina provide a unique opportunity to study this faunal transition at a fine stratigraphic scale within a radiometrically dated framework. In this study PI will oversee preparation of the complete skeleton of the important new early dinosaur, Eoraptor lunensis, and also generate more radiometric dates of the enclosing strata of this dinosaur. This work will shed light on an important point in tetrapod evolution.