NO ANIMAL WAS SAFE IN THE TRIASSIC: MULTIPLE PREDATION ATTEMPTS ON A LARGE (5-6 METER) CARNIVOROUS “RAUISUCHIAN” FROM THE LATE TRIASSIC OF NEW MEXICO

Hypotheses of past diets and feeding behaviors are informed by important, but rare, direct evidence of trophic interactions in the fossil record (e.g. bite marks). We present evidence of three independent predation events on a single femur from a large loricatan (=”rauisuchian”) from the Upper Triassic Chinle Formation (~210 MYA). The predation events consist of 1) at least one failed predation attempt by a large phytosaur; 2) a feeding event by a large predator at or soon after death; and 3) a second possible feeding event peri- or postmortem. Evidence of the first attack is in the form of partially healed punctures and a large embedded tooth crown (>5 cm in length based on CT data) in the proximolateral portion of the femur. We identify the tooth as phytosaurian based on a rounded cross section and a straight long axis. Reaction tissue in the punctures and surrounding the tooth indicates that the loricatan survived those injuries. The second event is represented by a group of bite marks on opposing sides of the femur; all are roughly 8 by 5 mm in size and fusiform, indicating that the trace maker’s teeth were laterally compressed and had carinae that possibly were serrated. The spacing and morphology of these marks indicates that the actor was a large predator, but the taxonomic identification is unclear. These bite marks exhibit obvious impact trauma with no reaction tissue, indicating that the attack occurred at or near time-of-death. The third event consists of scores present near midshaft that are oriented roughly perpendicular to the long axis of the femur. No reaction tissue is present, which suggests that this event also occurred at or after time-of-death. This specimen provides a rare opportunity to interpret ancient feeding and predation by multiple actors on a single prey animal over a period of the life and death history of that individual. Our analysis of this specimen indicates 1) loricatans had the potential to survive major predation attacks and 2) seemingly top predators clearly were targeted by other members of the fauna. Though the Late Triassic loricatans often are interpreted as top terrestrial predators in part because of their large size (most loricatans are ~3-6 m total length), the attacks recorded by this specimen demonstrate that size alone should not be the sole factor in determining trophic status.