Omomyids are a group of small-bodied, tarsier-like primates that lived on the northern continents between 56 and 34 million years ago. They represent the earliest known definitive primates in the fossil record, appearing slightly earlier than members of the other large Eocene primate lineage, Adapiformes. Paleontologists have now described new omomyid specimens from the Uinta Basin of Utah and the Tornillo Basin of Texas, the United States.
“Since fossil primates were first discovered in North America in the 1860s, only a handful of specimens from the late middle Eocene of Texas and Utah have been described,” said University of Texas at Austin’s Professor Chris Kirk.
“For the larger members of the extinct primate family Omomyidae, these small sample sizes have led to some confusion, with past authors unable to agree whether there are one, two or three genera represented.”
Omomyids initially had body masses below 500 grams, but some evolved to double that size during the late middle Eocene.
The two new species identified — from the genera Ourayia and Mytonius — are on the larger end of the spectrum.
They probably resembled present-day small to medium-size lemurs and consumed a diet of fruit and leaves.
Both new species appear to be endemic to the Tornillo Basin and differ from fossil primates found in other parts of North America.
“This distinctiveness of the West Texas primate community suggests that they were evolving at least partly in isolation, with perhaps relatively few opportunities for migration or gene flow with communities of primates living in other parts of North America at the same time,” Professor Kirk said.
“Eocene primates in the Big Bend may also have been adapting to the local environmental conditions.”
The researchers also expanded the fossil evidence of three previously discovered species — Diablomomys dalquesti, Mytonius hopsoni and Ourayia uintensis — painting a clearer picture of these primates’ anatomies…
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