Paleontologists at the University of Texas at Austin have identified three new species of omomyine primates that lived between 42 and 46 million years ago (Eocene epoch).

The three new species — named Ekwiiyemakius walshi, Gunnelltarsius randalli and Brontomomys cerutti — belong to Omomyinae, a subfamily of early primates.

The fossils came from the Friars Formation of San Diego County, southern California.

“Ekwiiyemakius walshi, the smallest of the three new species, had a mass of 113-125 grams, comparable in size to some modern bushbabies,” said University of Texas at Austin’s Professor Chris Kirk and graduate student Amy Atwater.

“The species is named for paleontologist Stephen Walsh from the San Diego Museum of Natural History, who collected and prepared many of the specimens from the Friars Formation, and also derives from the Native American Kumeyaay tribe’s place name, Ekwiiyemak — meaning ‘behind the clouds’ — for the location of the headwaters of the San Diego and Sweetwater Rivers.”

“Gunnelltarsius randalli is named for Gregg Gunnell, expert on Eocene mammals, and for San Diego Museum of Natural History fossil collections manager Kesler Randall. It had a mass of 275-303 grams, about the size of today’s fat-tailed dwarf lemur.”

“Brontomomys cerutti was large compared with most other omomyoids and had a mass of 719-796 grams, about the size of a living sportive lemur.”

“Due to its large size, its name derives from the Greek word brontē (thunder), as well as for Richard Cerutti, the retired San Diego Museum of Natural History paleontologist responsible for collecting many of the Brontomomys specimens.”

These findings increase the total number of known Eocene omomyine primates from 15 to 18.

“The addition of these primates provides for a better understanding of primate richness in the middle Eocene,” Atwater said.

“Previous research in the Rocky Mountain basins suggested the primate richness declined during this time period, but we argue that primate richness increased concurrently in other locations.”

The three new species are described in a paper published in the Journal of Human Evolution.

_____

Amy L. Atwater & E. Christopher Kirk. New middle Eocene omomyines (Primates, Haplorhini) from San Diego County, California. Journal of Human Evolution, published online August 24, 2018; doi: 10.1016/j.jhevol.2018.04.010