Human primate ancestors had transitional lemur-like grooming claw

Washington - Early primates may have traded their flat nails for raised claws due to functional purposes, a new study has suggested.

In a new study co-authored by a University of Florida researcher, the scientists examined the first extinct North American primate with a toe bone showing features associated with the presence of both nails and a grooming claw.

Study co-author Jonathan Bloch, an associate curator of vertebrate paleontology at the Florida Museum of Natural History on the UF campus, said the 47-million-year-old primate, Notharctus tenebrosus,

clearly had a grooming claw on its second digit. Surprisingly, the claw was somewhat flattened like a nail.

“Notharctus may provide evidence that nails did develop in this primate group, or it could be telling us that claws were developed from nails in this group, which would make them more lemur like,” Bloch said.

Lead author Stephanie Maiolino, an anthropology graduate student at Stony Brook University, said that the presence or lack of a grooming claw has previously been used to classify primate groups –

humans, apes and monkeys have nails, while lemurs have grooming claws in their second digit.

“But it’s not clear that lacking a grooming claw means a species is related to anthropoids, which is the primate group that includes apes, humans and monkeys,” Maiolino said.

The toe bone described in the new study has claw-like features near the base, but the tip is more flat, much like a modern monkey nail.

Study co-author Doug Boyer, an assistant professor of physical anthropology at Brooklyn College in New York, said the primate was “either in the process of evolving a nail and becoming more like

humans, apes and monkeys, or in the process of evolving a more lemur-like claw.”

“I now believe it’s more likely that nails were the starting point and grooming claws developed as a functional trait,” Boyer said.

The study has been published in the journal PLoS ONE.