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Earliest Primate Skeleton And ‘Cousin’ Of Human Ancestor Discovered In China

An international team of paleontologists has discovered a nearly complete, articulated skeleton of a tiny tree-dwelling primate in China.

| June 7, 2013 | In the Lab

AsianScientist (Jun. 7, 2013) - An international team of paleontologists has discovered a nearly complete, articulated skeleton of a new tiny, tree-dwelling primate dating back 55 million years. The Eocene Epoch fossil, one of the most primitive primate fossils ever documented, was recovered from Hubei Province in central China.

The research team, led by Xijun Ni of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) at the Chinese Academy of Sciences in Beijing, describes the fossil in the latest edition of the journal, Nature.

A 3D, high-resolution reconstruction of the skeleton of Archicebus achilles. (Photo: Paul Tafforeau/ESRF and Xijun Ni/IVPP/CAS)
A 3D, high-resolution reconstruction of the skeleton of Archicebus achilles, aided by X-ray (Photo: Paul Tafforeau/ESRF and Xijun Ni/IVPP/CAS)

Ni said that while doing fieldwork years ago in Hubei Province, he first came across the fossil, which had been found by a local farmer and was later donated to the IVPP. The fossil was encased within a rock and discovered after the rock was split open, yielding fossils and impressions of the primate on each side of the two halves.

It was discovered in a quarry that had once been a lake and is known for producing ancient fish and bird fossils from the Eocene Epoch. The quarry is near Jingzhou City, south of the Yangtze River, and about 270 kilometers southwest of Wuhan City, the province capital.

"This region would have been a large series of lakes, surrounded by lush tropical forests during the early Eocene," Ni said.

The fossil has been named Archicebus achilles. The genus, Archi, is Greek for the beginning, and the prefix is attached to cebus, which translates to “long-tailed monkey,” after the long tail of the fossil skeleton. The species name, Achilles, is an allusion to its interesting heel anatomy and named after the mythological Greek warrior, Achilles.

"Archicebus marks the first time that we have a reasonably complete picture of a primate close to the divergence between tarsiers and anthropoids," Ni said. "It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution."

The tiny primate has a body that is around 71 mm long and its estimated weight is around 20–30 grams, as small as a modern pygmy mouse lemur. Certain features of the skeleton suggest that the creature was a frequent leaper, favouring four-limbed grasp-leaping as a mode of transport. Small pointy teeth indicate that it ate insects. Large eye sockets indicate that the creature had good vision for hunting, but evidence points towards a diurnal rather than nocturnal activity pattern.

Analysis of the skeleton reveals a mixture of features — some that resemble anthropoids and some that resemble tarsiers. The most unusual aspect of Archicebus is its foot anatomy: it has typical robust grasping big toes, long toes and nailed digits of primitive arboreal primates, but also advanced monkey-like heel bones and long metatarsals not normally found in a primitive early Eocene fossil primate.

These findings show that the age of the split between the Tarsiiformes and anthropoids, from which humans descend, is earlier than previously thought. The creature seems to be the earliest and most primitive known relative of the tarsiers. As tarsiers are related to anthropoids — the primates that include monkeys, apes and humans — the discovery shows that the lineage leading ultimately to humans was distinct at a very early date.

Although primitive primate fossils have been discovered on several continents, including North America, the discovery of Archicebus and other ancient fossils in China point to Asia as the continent where primates originated.

"In the past, many scientists believed that Africa was the continent of origin for all primates, but it appears over the last decade that Asia is the more likely continent of origin, and this new skeleton supports that view," said Northern Illinois University anthropologist Dan Gebo, a co-author on the study.

The article can be found at: Ni X et al. (2013) The oldest known primate skeleton and early haplorhine evolution.


Source: NIU; Photo: Mat Severson/NIU.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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