DENTITION AND DIET IN WYOMING OXYAENIDS

Oxyaenids were cat-like creodonts and were likely among the top predators of the Paleogene. Though they were distributed across Eurasia and North America, their fossil record is especially rich in Paleocene and early Eocene sites from the Rocky Mountain states, where they have been the basis of numerous paleoecological and evolutionary analyses. An increase in oxyaenid body size through time has made them a classic example of Cope’s Rule. This size increase may have been the result of an evolutionary ratchet, in which a hypercarnivorous lifestyle selected for increasingly large body sizes. If this were the case, the relative length of the shearing blade on oxyaenid cheek teeth – a possible indicator of hypercarnivory – should be expected to increase through time as well. To test this prediction, we used an existing data set of linear measurements of oxyaenid dentition from Eocene sites in Wyoming and surrounding states. Members of two putative oxyaenid lineages were present in this data set (Oxyaena forcipata-Oxyaena gulo and Patriofelis ulta-Patriofelis ferox), allowing us to compare relative blade length in fourth upper premolars and first upper molars within two possible ancestor-descendant sequences. Preliminary results suggest no significant change in blade length within either lineage. While these results tentatively support the hypothesis that body size increase was driven by factors other than just dietary specialization, it is important to note that the sample of specimens included in this data set is small. Furthermore, carnassial morphology in extant carnivorans often reflects a phylogenetic rather than dietary signal. This may have been the case in creodonts as well, in which case relative blade length might be expected to remain stable through time. Further analysis of the oxyaenid dentition will establish how widespread this decoupling of relative blade length and body size is and could shed light on oxyaenid behavior and ecology.