'Three unknown ancient primates identified'

Scientists say they have identified three new species of ancient primates that were previously unknown to science.

The primates lived 42 million to 46 million years ago, said researchers from The University of Texas at Austin in the US.

Primates is a group that consists of all the species commonly related to the lemurs, monkeys, and apes, including humans.

The species, described in the Journal of Human Evolution, were residents of San Diego County in the US at a time when southern California was filled with lush tropical forests.

The researchers named these new species Ekwiiyemakius walshi, Gunnelltarsius randalli and Brontomomys cerutti.

These findings double the number of known primate genera represented in the Friars Formation in San Diego County and increase the total number of known omomyine primates of that period from 15 to 18.

"The addition of these primates provides for a better understanding of primate richness in the middle Eocene," said UT Austin graduate student Amy Atwater, who is now at the Museum of the Rockies in the US.

Studying the teeth, researchers concluded the three new genera range in size from 113 to 796 grammes and are most likely related to a group of extinct species comprising the primate subfamily Omomyinae.

Ekwiiyemakius walshi, the smallest of the three new species, was estimated to weigh between 113 and 125 grammes - comparable in size to some modern bushbabies.

Gunnelltarsius randalli was estimated to weigh between 275 and 303 grammes, about the size of today's fat-tailed dwarf lemur.

Brontomomys cerutti was large compared with most other omomyoids and was estimated to weigh between 719 and 796 grammes - about the size of a living sportive lemur.