Meeting Abstract

P3.178  Monday, Jan. 6 15:30  Comparing skeletal characteristics of fossil Equus and modern mustangs MCHORSE, B.K.*; HOPKINS, S.S.B.; Harvard University; University of Oregon bmchorse@fas.harvard.edu

Modern horses (genus Equus) provide an opportunity to investigate the morphological effects of differing selective pressures. For example, domesticated horse breeds (E. caballus) experience strong artificial selection in different directions depending on their intended use; free-ranging feral horses (E. caballus) were previously domesticated, but are now under natural selection; and wild equids (E. kiang, E. grevyi, and others) have undergone natural selection without domestication. Modern horses also provide a useful data-rich study system for investigating the transition from three toes to a single toe in the fossil record of equids (e.g., by providing a source of information on soft tissues and gait dynamics in addition to the skeleton). North American mustangs are feral horses that range free on government land in the western United States. They are abundant and periodically collected in roundups, where individuals from the herd are auctioned to the public to be tamed; this makes it possible to collect data from naturally selected horses that are also accustomed to being handled. Previous work has shown mustangs differ significantly in gross skeletal structure from a group of artificially selected competition horses, but it is unknown how morphologically similar mustangs are to wild horses. We compare postcranial measurements of mustangs and fossil Equus specimens to gain a broad-level insight on this question. If they are not significantly different from wild horses in their skeletal structure, mustangs represent an abundant, convenient source of modern data that may be better suited to answering evolutionary questions than data from artificially-selected domestic horses.