Researchers Discover Oldest Fossil Primate Skeleton
June 5, 2013

Researchers Discover Oldest Fossil Primate Skeleton

Brett Smith for — Your Universe Online

An international team of researchers has discovered the oldest known fossil primate skeleton, which could shed light of the evolutionary divergence between the lineage leading to modern monkeys, apes and humans on one side and the lineage leading to tarsiers on the other.

According to a report of the discovery in the journal Nature, the fossil was found in an ancient Chinese lakebed, near the course of the modern Yangtze River.

The scientists determined that the skeleton, dubbed Archicebus Achilles, is about seven million years older than the previous oldest fossil primate skeletons that were found in Germany and Wyoming.

"Archicebus differs radically from any other primate, living or fossil, known to science. It looks like an odd hybrid with the feet of a small monkey, the arms, legs and teeth of a very primitive primate, and a primitive skull bearing surprisingly small eyes,” said Christopher Beard, a curator at the Carnegie Museum. “It will force us to rewrite how the anthropoid lineage evolved."

Statistical analyses determined that Archicebus would have weighed about one ounce and been slightly smaller than pygmy mouse lemurs from Madagascar, the smallest living primates.

"The tiny size and very basal evolutionary position of Archicebus support the idea that the earliest primates, as well as the common ancestor of tarsiers and anthropoids, were miniscule,” said Daniel Gebo, an expert on the evolution of primate anatomy at Northern Illinois University. “This overturns earlier ideas suggesting that the earliest members of the anthropoid lineage were quite large, the size of modern monkeys."

"Even though Archicebus appears to be a very basal member of the tarsier lineage, it resembles early anthropoids in several features, including its small eyes and monkey-like feet,” said Marian Dagosto, a biology professor at Northwestern University. “It suggests that the common ancestor of tarsiers and anthropoids was in some ways more similar than most scientists have thought."

The fossil was found in a layer of sedimentary rock that was deposited in an ancient lake approximately 55 million years ago, when much of the world was experiencing a warming period that included tropical rainforests covering much of the planet.

To study the fossil, the scientific team scanned the specimen at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Using the synchrotron scans, the team was able to create a three-dimensional digital reconstruction of the small, fragile skeleton in elaborate detail.

"During the past few years, we at the ESRF have developed the technology to look at those parts of the fossil that are still buried in the rock at a level of detail that is unique in the world. Speaking virtually, we made the skeleton stand up," said Paul Tafforeau, a Synchrotron CT scanning expert.

"People may see this simply as another discovery of a well preserved fossil, but to reveal the remarkable secrets that have been hidden in the rock for millions of years, we undertook extensive work, applied state-of-the-art technology, and intensive international cooperation took place behind the scenes at several museums. It took us ten years,” said John Flynn, curator of the American Museum of Natural History.