Most adapiform primates from North America are members of an endemic radiation of notharctines. North American notharctines flourished during the Early and early Middle Eocene, with only two genera persisting into the late Middle Eocene. Here we describe a new genus of adapiform primate from the Devil’s Graveyard Formation of Texas. Mescalerolemur horneri, gen. et sp. nov., is known only from the late Middle Eocene (Uintan) Purple Bench locality. Phylogenetic analyses reveal that Mescalerolemur is more closely related to Eurasian and African adapiforms than to North American notharctines. In this respect, M. horneri is similar to its sister taxon Mahgarita stevensi from the late Duchesnean of the Devil’s Graveyard Formation. The presence of both genera in the Big Bend region of Texas after notharctines had become locally extinct provides further evidence of faunal interchange between North America and East Asia during the middle Eocene. The fact that Mescalerolemur and Mahgarita are both unknown outside of Texas also supports prior hypotheses that low-latitude faunal assemblages in North America demonstrate increased endemism by the late middle Eocene.
Adaptive shifts associated with human origins are brought to light as we examine the human fossil record and study our own genome and that of our closest ape relatives. However, the more ancient roots of many human characteristics are revealed through the study of a broader array of living anthropoids and the increasingly dense fossil record of the earliest anthropoid radiations. Genomic data and fossils of early primates in Asia and Africa clarify relationships among the major clades of primates. Progress in comparative anatomy, genomics, and molecular biology point to key changes in sensory ecology and brain organization that ultimately set the stage for the emergence of the human lineage.
New omomyid fossils from the Purple Bench locality of the Devil’s Graveyard Formation, middle Eocene (Uintan) of southwest Texas, are described. One specimen represents a new genus and species, herein named Diablomomys dalquesti. This new species is allocated to the tribe Omomyini, sister taxon to Omomys and Chumashius. A second specimen represents a range extension of the Utah species Mytonius hopsoni to the Trans-Pecos region of Texas. Previously, only one omomyid species (Omomys carteri) had been documented from Purple Bench and other late Uintan localities in the Devil’s Graveyard Formation. These new omomyid fossils are of particular significance because Purple Bench is stratigraphically intermediate between the older late Bridgerian/early Uintan localities and the younger Duchesnean localities of Trans-Pecos Texas. With a more southerly location in the continental United States, the Devil’s Graveyard Formation amplifies our understanding of patterns of North American primate richness at a time when the higher-latitude sites of the western interior were undergoing significant climatic cooling and increases in seasonality with commensurate faunal reorganization. Although the Uintan (approximately 46.5–40 Ma) was a time in which anaptomorphine richness decreased dramatically, the results of this analysis suggest that Uintan omomyine richness is higher than was previously appreciated, particularly at lower latitudes.