Meeting Abstract
P3.103 Sunday, Jan. 6 Body size reconstruction in a saber-toothed cat from the Late Miocene of North America HOPKINS, SSB*; ORCUTT, JD; DAVIS, EB; U. of Oregon; U. of Oregon; U. of Oregon shopkins@uoregon.edu
The Late Miocene is a critical interval in felid evolution in North America, falling at the end of the “Cat Gap” and encompassing the immigration of the saber-toothed Machairodus from Eurasia, the evolution of the enigmatic, endemic Nimravides, and the appearance of the continent’s first true conical-toothed cats. Because of their value in reconstructing evolutionary trends and behavior, much of the research on Late Miocene felids has focused on cranial and dental remains. However, postcrania are also valuable tools in reconstructing the diversity and ecology of felids from this interval. Limb bones from the Northwest and Great Plains indicate the presence of an aberrantly large felid during the Hemphillian land mammal age. The morphology of these bones is similar to that of Machairodus; however, they are up to 35% larger than known specimens of North American Machairodus. Length of a complete humerus from McKay Reservoir, Oregon yields a body mass estimate of 228 kg, making it larger than all but a few captive individuals of extant lions and tigers, but an estimate based on circumference (415 kg), suggests that the robust forelimbs of machairodontines may overpredict body size. Regardless of its precise mass, the McKay felid was undoubtedly much larger than its contemporaries, and was in a size class without precedent on the continent. It is unlikely that the difference in size between the large felid and Machairodus reflects regional variability, as both have been recovered from the same sites. The large felid may indicate the presence of sexual dimorphism in Machairodus, or it may indicate the presence of an as-yet unrecognized species of felid. In either case, it has important implications for the diversification of felids in North America and underscores the importance of postcrania in understanding taxa previously known described mainly from skulls.
