Felids are keystone predators in modern ecosystems and likely played a similar role in shaping ecosystems through the Cenozoic. Unfortunately, understanding the paleoecological impact of felids has been hampered by taxonomic confusion and uncertainty in big cat diversity through time. This stems, in part, from the importance of dentition in differentiating feliform taxa combined with the abundance of postcrania in the fossil record. This dilemma is best illustrated by the humeri of a very large felid uncovered from a number of Hemphillian-aged localities in North America that, in the absence of craniodental remains, have not previously been definitively identified. We present the results of an analysis of the potential of isolated distal humeri to identify feliform taxa. We compared the form and size of distal humeri across feliforms using geometric morphometric analysis and used linear measurements to reconstruct body mass and estimate prey size. Our results suggest that distal humeri are useful tools for differentiating feliform families, genera, and species. Further, along with a specimen from Idaho with associated dentition, they suggest that the large Hemphillian-aged felid is a new species of Machairodus. Future phylogenetic analyses will be necessary to reconstruct the evolutionary history of North American Machairodontinae, but this new taxon provides evidence for a diverse predator fauna during the late Miocene of North America that included some of the largest felids in Earth history.

猛禽是现代生态系统中的主要掠食者，并且可能通过新生代在塑造生态系统中发挥了类似的作用。不幸的是，由于时间上的分类混乱和大猫多样性的不确定性，阻碍了人们对猫科动物的古生态影响的理解。这部分是由于牙列在区分花样分类群中的重要性以及化石记录中大量的克拉克特后遗症。北美两汉族地区发现的非常大的猫科动物的肱骨最能说明这一难题，因为在没有颅牙遗留物的情况下，以前还没有确定过这种猫科动物。我们提出了孤立的远端肱骨识别fe形类群的潜力的分析结果。我们使用几何形态计量学分析比较了跨越整个卵形的肱骨远端的形式和大小，并使用线性测量来重建体重并估计猎物的大小。我们的结果表明，肱骨远端是区分useful形科，属和种的有用工具。此外，连同爱达荷州的一个带有相关齿系的标本一起，他们表明，大型的汉普伦时代的猫科动物是一种新的齿科动物。Machairodus。未来的系统发育分析对于重建北美Machairodontinae的进化史将是必要的，但是这种新的分类单元为北美中新世晚期的食肉动物区系提供了证据，其中包括地球历史上一些最大的猫科动物。