New specimens of middle Eocene omomyines (Primates, Omomyoidea) from the Uinta Basin of Utah and the Tornillo Basin of Texas, with clarification of the generic status of Ourayia, Mytonius, and Diablomomys

E Christopher Kirk; Rachel H Dunn; Benjamin Rodwell; K E Beth Townsend

doi:10.1016/j.jhevol.2023.103425

New specimens of middle Eocene omomyines (Primates, Omomyoidea) from the Uinta Basin of Utah and the Tornillo Basin of Texas, with clarification of the generic status of Ourayia, Mytonius, and Diablomomys

J Hum Evol. 2023 Oct:183:103425. doi: 10.1016/j.jhevol.2023.103425. Epub 2023 Sep 20.

Authors

E Christopher Kirk¹, Rachel H Dunn², Benjamin Rodwell³, K E Beth Townsend⁴

Affiliations

¹ Department of Anthropology, The University of Texas at Austin, 2201 Speedway Stop C3200, Austin, TX 78712, USA; Department of Geological Sciences, The University of Texas at Austin, 2275 Speedway Stop C9000, Austin, TX 78712, USA; Jackson School Museum of Earth History, The University of Texas at Austin, J. J. Pickle Research Campus, 10100 Burnet Road, PRC 6-VPL, R7600, Austin, TX 78758, USA. Electronic address: eckirk@austin.utexas.edu.
² Department of Anatomy, Des Moines University, 3200 Grand Avenue, Des Moines, IA 50312, USA.
³ Department of Anthropology, The University of Texas at Austin, 2201 Speedway Stop C3200, Austin, TX 78712, USA.
⁴ Department of Anatomy, College of Graduate Studies, Midwestern University, 19555 N. 59th Avenue, Glendale, AZ 85308, USA.

PMID: 37734122
DOI: 10.1016/j.jhevol.2023.103425

Abstract

In the middle Eocene, multiple lineages of North American omomyoids independently evolved body masses greater than 500 g. Most of these large-bodied omomyoids are known from small sample sizes, which has contributed to a lack of consensus regarding their alpha taxonomy. Here, we describe new Uintan omomyine specimens from the Uinta Basin of Utah and the Tornillo Basin of Texas. These new samples expand the hypodigms of Diablomomys dalquesti, Mytonius hopsoni, and Ourayia uintensis, and favor the recognition of new species of Mytonius and Ourayia based on specimens from the Tornillo Basin. These samples support the recognition of Diablomomys as a valid genus distinct from Omomys, Ourayia as a valid genus distinct from Macrotarsius, and Mytonius as a valid genus distinct from Ourayia. Although Diablomomys and Omomys co-occur in the late Uintan of the Tornillo Basin, Ourayia and Mytonius are time-successive taxa with a wide distribution across multiple Laramide basins. The data presented here reinforce the conclusion that the Uintan was a time period in which omomyines diversified to include a large number of taxa with body masses above Kay's threshold and frugivorous-folivorous diets. These data also provide evidence that North American primate faunas exhibited a shifting pattern of regional endemism during the middle Eocene. By the early Uintan, primate faunas from Southern California were already quite distinct from primate faunas of the central Rocky Mountains or Trans-Pecos Texas. By the late Uintan, primate faunas in all three regions demonstrated greater provincialism, with Trans-Pecos Texas and Southern California both exhibiting a large number of endemic primate taxa and sharing only a single primate genus (Macrotarsius) in common. This increase in primate endemism across the Uintan may be tied to changes in paleohabitats associated with the larger trend toward decreasing temperatures from the Early Eocene Climatic Optimum to the Eocene/Oligocene transition.

Keywords: Devil's Graveyard Formation; Haplorhine; Laramide Basin; Omomyid; Primate; Uintan NALMA.