DESCRIPTION OF A PUNCTURE TOOTH TRACE ON A PHYTOSAUR ILIUM FROM THE CHINLE FORMATION (UPPER TRIASSIC), ARIZONA

Phytosaurs are extinct archosauriforms found in Upper Triassic layers all over the world, with many showing up in the Chinle Formation of the southwestern United States. This study specifically looked at the right ilium of a phytosaur that may have been Smilosuchus adamanensis (PEFO 34841), using pictures of the medial and lateral views. This specimen was found in the Martha’s Butte beds of the Sonsela Member of the Chinle Formation of Petrified Forest National Park, Arizona. The ilium has a nearly circular depression on the lateral surface at the base of the posterior iliac blade. Based on the morphology of the depression and the fact that it broke through the cortical bone, we determined that it is a puncture. There are two small holes within the puncture. The puncture is 3.3 mm deep, but as the specimen was not completely prepared, it might go deeper than that. There is some discoloration on the medial side of the bone opposite the site of the puncture, as well as a long fracture running through the bite mark. This bite mark can be helpful in understanding intraspecific interactions, as we think this injury may have been inflicted by another phytosaur. Without more of the skeleton, it is difficult to tell whether the bite was related to feeding or some kind of aggressive behavior.