Tiny Primate Fossil is Oldest Ever Found, Yields Clues to Primate Origins

A nearly-complete skeleton of a palm-sized primate that lived about 55 million years ago is being hailed as the oldest known member of the primate family and may lead to new insights into the origins of primates and humans alike.

Named Archicebus achilles, which roughly means "original long-tailed monkey," the creature had a human-like face and feet, and is considered a member of the tarsiiforme family of small tree-dwelling primates, which includes lemurs.

Archicebus' age suggests that even 55 million years ago, there was a genealogical split between the tarsiers and the anthropoid group of primates. The find adds credence to the idea that the anthropoid primates -- the group which includes modern-day monkeys, apes and humans -- also appeared at least 55 million years ago.

Study author Christopher Beard, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, told Nature that because the fossil indicates that the tarsier and anthropoid primate groups split before that era, the anthropoid lineage is also at least that old.

Also of note is the creature's features, which included tarsier-like teeth and bones and anthropoid-like heel and feet bones.

"This mosaic of features hasn't been seen before in any living or fossil primate," Beard said.

Study author Ni Xijun of the Beijing-based Institute of Vertebrate Paleontology and Paleoanthropology, further emphasized the Archicebus' striking appearance in an interview with Bloomberg Businessweek

"This creature is very bizarre, it has a combination of features from tarsiiformes and from anthropoids," Ni said. "It also has nails on all its fingers and toes, a rounded face and brain case, very short snout, and front-facing eyes unlike with other small creatures."

Ni said that not much is known about early anthropoid, but the Archicebus fossil offers quite a lot of information about tarsiiformes. "We can deduce that the earliest anthropoid could be very similar," Ni explained.

The Archicebus fossil, which was exquisitely well-preserved, was actually discovered about a decade ago by a farmer in China's Hubei Province. Recognizing the significance of the find, researchers took their time in describing and analyzing the fossil.

The creature lived 10 million years after the extinctions of the dinosaurs, which puts it in striking range as a candidate for the earliest of human ancestors.

"If you retrace primate evolution to its beginning, [Archicebus] is what our ancestors most likely looked like," according to Zhe-Xi Luo, a vertebrate palaeontologist at the University of Chicago in Illinois, who also spoke to Nature.

The research is published in the journal Nature.