Fossil Sheds Light on Early Primates: Partial Skeleton near Root of Monkey, Ape and Human Line

Article excerpt

A palm-sized creature sporting a tail longer than its body has given scientists an unprecedented look at one of the earliest phases of primate evolution.

An international team led by paleontologist Xijun Ni of the Chinese Academy of Sciences in Beijing analyzed this animal's 55-million-year-old remains, the oldest known primate skeleton. Discovered 10 years ago along an ancient lake bed in central China, the fossil comes from a previously unknown genus and species, Archicebus achilles, the scientists report June 6 in Nature.

Over the past decade, digital scanning of the find with X-rays enabled the scientists to assemble a 3-D reconstruction of the fragile skeleton.

Archicebus was the earliest member of a group that eventually evolved into tarsiers, small primates that now live in Southeast Asia, Ni says. The skeleton includes some unexpected features, however, that look less like tarsiers and more like ancient anthropoids, the primate precursors of monkeys, apes and humans. These traits include small eyes and monkeylike feet.

"Archicebus marks the first time that we have a reasonably complete picture of a primate close to the evolutionary divergence of tarsiers and anthropoids," Ni says. That split probably occurred between 60 million and 55 million years ago, he estimates.

Researchers suspect that primates first evolved sometime between 85 million and 65 million years ago, around the time of the dinosaurs' demise. …