New fossil evidence sheds light on evolution of early primates in North America

Researchers from The University of Texas at Austin, Des Moines University in Iowa, and Midwestern University in Arizona have unveiled exciting findings from fossil evidence in the Tornillo Basin of West Texas and the Uinta Basin in Utah. This discovery introduces two new species of omomyids, which are early primates from the Eocene epoch, while also resolving previous disputes about their taxonomy.

Published in the Journal of Human Evolution, this study not only expands our knowledge of primates in these regions but also confirms the existence of three distinct genera of omomyids.

Chris Kirk, a professor of anthropology at UT and the paper’s lead author, explained, “Fossil primates in North America have been a rare find since the 1860s, particularly in the late middle Eocene of Texas and Utah. This scarcity has led to confusion among researchers about whether there are one, two, or three genera of the larger omomyids.”

Omomyids, initially small-bodied creatures with masses below 500 grams, evolved to larger sizes during the late middle Eocene. The two newly identified species, belonging to the genera Ourayia and Mytonius, fall on the larger end of this spectrum, resembling modern small to medium-sized lemurs. They likely had a diet consisting of fruit and leaves.

These new species are unique to the Tornillo Basin and differ from fossil primates found in other parts of North America. This distinctiveness suggests that they evolved in relative isolation, with limited opportunities for migration or gene flow with other primate communities elsewhere in North America during the same period.

The study also enhances our understanding of three previously known species—Diablomomys dalquesti, Mytonius hopsoni, and Ourayia uintensis—providing clearer insights into their anatomies and diets.

While previous research on Eocene primates primarily focused on earlier periods and regions with more abundant fossil samples, such as Wyoming’s Bighorn and Bridger basins, this discovery emphasizes the importance of studying primates from different regions to uncover how changing environmental factors influenced diverse populations.

Chris Kirk concluded, “The fact that, more than 150 years after the first Eocene primates were described in North America, we can find new fossil primate species in the Big Bend region, just eight hours from my home in Austin, is still astonishing to me. This underscores the many gaps in the fossil record and the numerous paleontological discoveries that await, often right in our own backyards.”

Source: University of Texas at Austin

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