SARMATOSUCHUS AND THE EARLY HISTORY OF THE ARCHOSAURIA

A detailed description of the early archosaur Sarmatosuchus otschevi S ennikov, 1994, from the Middle Triassic Donguz Formation of southern E uropean Russia, is presented. New morphological data forms the basis o f a preliminary investigation of the phylogenetic relationships betwee n a selection of the earliest archosaurs. A parsimony analysis based o n 9 taxa and 35 characters recovers two most parsimonious trees that s upport the referral of Sarmatosuchus and Fugusuchus to a proterosuchid clade, as well as the paraphyly of the Proterosuchia. Characters from the structure of the braincase are more homoplastic than those from t he rest of the skeleton. The presence of Sarmatosuchus in the Middle T riassic affords evidence that the proterosuchids were a more diverse a nd persistent clade than has been previously envisaged. Evidence sugge sting that proterosuchids may have existed with erythrosuchids and ear ly crown-group archosaurs in the Middle Triassic requires a revision o f our understanding of the early part of the archosaurian radiation.