Almost complete primate fossil described

Ida provides details about life in the Eocene

Forget Botox and tummy tucks. A little volcanic ash in Germany kept a 47-million-year-old small primate fossil from the Eocene looking pretty darn good. The 95-percent-complete skeleton is the most complete fossil primate ever found, researchers report online May 19 in PLoS ONE, and it offers an unparalleled glimpse at the life and times of an early primate.

COMPLETE The near-complete fossilized skeleton of 47-million-year-old Ida, Darwinius masillae, offers a rare glimpse of early primate life. Franzen et al., PLoS ONE 2009

A photograph (left) and X-ray (right) of Ida’s hands show five fingers, including opposable thumbs, which endowed her with a good grip. Franzen et al., PLoS ONE 2009

“When it comes to spectacular specimens, you don’t get more spectacular than this one,” says Richard Kay, a paleontologist at Duke University in Durham, N.C.

Since its debut, some have heralded the small primate, named Ida, as a missing link in human evolution. But, “We don’t think this particular fossil or species is the direct ancestor of humans,” says study coauthor Holly Smith of the University of Michigan in Ann Arbor. More research will be needed to understand where the fossil fits into the primate picture, she says.

Kay adds that, in his opinion, nothing about the fossil would overturn the prevailing view of primate evolution.

More formally Darwinius masillae, Ida was only three feet long from tip to tail and likely lived in trees of an ancient rain forest. Researchers think she may have been nocturnal, judging from the relatively large size of her eye sockets. Ida had nails instead of claws, short limbs and opposable thumbs, all hallmarks of primates.

The precise composition of the volcanic deposits in which Ida was found even allowed preservation of her soft tissue. “You can see the fur, the ears, all of the gut contents [leaves and a fruit], all the fingertips and toes,” Smith says.

Smith and her colleagues were able to guess Ida’s age based on the fossil’s teeth. “She was just turning over and replacing her baby teeth in the front of her face, and the molars were coming in the back,” Smith says. Because Ida had many teeth forming at the same time, Smith thinks the primate must have grown up fast, developing much quicker than a human would. Ida died before she was 1 year old, Smith and her colleagues suggest. Comparisons with a similar animal, the squirrel monkey, led the researchers to guess that Ida might have lived for 15 or 20 years had she not met an early demise.

“This really shows us what a whole primate was like at this time, when we see the first modern primates,” Smith says. Only a mummy or a recent intentional burial would produce a specimen as complete as Ida. (For comparison, the famed Lucy fossil from Ethiopia is only 40 percent complete.)

“There’s a lot of information in the fossil, even if it’s a great aunt or a great cousin,” Smith says.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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