Elbow-joint morphology in the North American ‘cheetah-like’ catMiracinonyx trumani

Abstract

The North American cheetah-like catMiracinonyx trumaniis an extinct species that roamed the Pleistocene prairies 13 000 years ago. AlthoughM. trumaniis more closely related to the cougar (Puma concolor) than to the living cheetah (Acinonyx jubatus), it is believed that bothA. jubatusandM. trumanipossess a highly specialized skeleton for fast-running, including limbs adapted for speed at the expense of restricting the ability of prey grappling. However, forelimb dexterity ofM. trumanihas not been yet investigated. Here, we quantify the 3D-shape of the humerus distal epiphysis as a proxy for elbow-joint morphology in a sample of living cats to determine whether the extinctM. trumaniwas specialized to kill open-country prey using predatory behaviour based on fast running across the prairies and steppe terrains of the North American Pleistocene. We show thatM. trumanihad an elbow morphology intermediate to that ofP. concolorandA. jubatus, suggesting thatM. trumanihad a less specialized pursuit predatory behaviour thanA. jubatus. We propose thatM. trumaniprobably deployed a unique predatory behaviour without modern analogues. Our results bring into question the degree of ecomorphological convergence betweenM. trumaniand its Old World vicarA. jubatus.