WEINBAUM, Jonathan; Texas Tech University: A reassessment of the systematics of rauisuchids and poposaurids (Archosauria: Crurotarsi)

The systematics of poposaurid and rauisuchid archosaurs is not well understood, particularly in relation to crocodylomorphs. The monophyly of both groups has also been questioned by several authors. Confusion stems in part due to a lack of complete descriptive work on key taxa. The terms poposaurid and rauisuchid are often used interchangeably in the literature, further confusing the taxonomy of these animals. New work on Postosuchus and a new specimen of Poposaurus help to polarize characters for a phylogenetic analysis. A data matrix of 34 characters for several selected Triassic taxa commonly referred to as poposaurids and rauisuchids, along with phytosaurs, aetosaurs and crocodylomorphs was used to present a new hypothesis of relationships. The data was analyzed in a bootstrap analysis with 100 replicates using a branch-and-bound search of PAUP. A strict consensus cladogram was produced indicating that poposaurids and rauisuchids are both monophyletic groups with crocodylomorphs more closely related to rauisuchids than poposaurids.