Hindlimb adaptations in Ourayia and Chipetaia, relatively large-bodied omomyine primates from the Middle Eocene of Utah
Article first published online: 14 APR 2006
Copyright © 2006 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 131, Issue 3, pages 303–310, November 2006
How to Cite
Dunn, R. H., Sybalsky, J. M., Conroy, G. C. and Rasmussen, D. T. (2006), Hindlimb adaptations in Ourayia and Chipetaia, relatively large-bodied omomyine primates from the Middle Eocene of Utah. Am. J. Phys. Anthropol., 131: 303–310. doi: 10.1002/ajpa.20407
- Issue published online: 27 SEP 2006
- Article first published online: 14 APR 2006
- Manuscript Accepted: 6 OCT 2005
- Manuscript Received: 10 JUL 2005
- primate evolution;
- functional morphology;
- Uinta Formation
North American omomyids represent a tremendous Eocene radiation of primates exhibiting a wide range of body sizes and dietary patterns. Despite this adaptive diversity, relatively little is known of the postcranial specializations of the group. Here we describe hindlimb and foot bones of Ourayia uintensis and Chipetaia lamporea that were recovered from the Uinta B member (early Uintan Land Mammal Age), Uinta Formation, Utah. These specimens provide insights into the evolution of postcranial adaptations across different body sizes and dietary guilds within the Eocene primate radiation. Body mass estimates based on talar measurements indicate that Ourayia uintensis and Chipetaia lamporea weighed about 1,500–2,000 g and 500–700 g, respectively. Skeletal elements recovered for Ourayia include the talus, navicular, entocuneiform, first metatarsal, and proximal tibia; bones of Chipetaia include the talus, navicular, entocuneiform, and proximal femur. Both genera had opposable grasping big toes, as indicated by the saddle-shaped joint between the entocuneiform and first metatarsal. Both taxa were arboreal leapers, as indicated by a consistent assemblage of characters in all represented bones, most notably the somewhat elongated naviculars, the high and distinct trochlear crests of the talus, the posteriorly oriented tibial plateau (Ourayia), and the cylindrical head of the femur (Chipetaia). The closest resemblances to Ourayia and Chipetaia are found among the Bridger omomyines, Omomys and Hemiacodon. The results of our comparisons suggest that the later, larger, more herbivorous omomyines from Utah retained a skeletal structure characteristic of earlier, smaller North American omomyids. Am J Phys Anthropol, 2006. © 2006 Wiley-Liss, Inc.