DIGGING UP CHARACTERS OF THE ILIUM TO DISTINGUISH PHYTOSAUR TAXA

Taxonomic and phylogenetic research on phytosaurs, a group of crocodile-like reptiles found in Triassic rocks, has centered around morphological variation in the skull and has resulted in competing phylogenies. To better understand the relationships of phytosaurs, further research is needed on their postcrania. We developed seven morphological characters based on characters previously discussed in the literature and from our own observations. The characters are: 1) ratio of total length to total height, 2) shape of anterior iliac blade (rounded or pointed at the tip), 3) deflection of the anterior iliac blade (dorsal or ventral), 4) ratio of the length of the posterior process from its tip to the point of maximum curvature of the posterior iliac notch compared to the rest of the iliac blade (posterior iliac notch to anterior process), 5) presence of a ventral pubic process, 6) shape of the dorsal margin (concave, flat, convex, or sigmoidal), and 7) deflection of the posterior iliac blade (ventral or dorsal). We applied our characters to specimens from Petrified Forest National Park and the University of California Berkeley, and our preliminary observations revealed certain traits that are useful in distinguishing different species. We will be traveling to the East Coast to continue our study and apply our characters to more phytosaur ilia, with the goal of clearing up aspects of phytosaur taxonomy.