© Xijun Ni, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences
The skeleton of Archicebus achilles, shown in this artist's sketch, is among the best-preserved examples of early primates.
The oldest well-preserved skeleton of a primate, a 55-million-year-old specimen found in China, has been discovered, researchers report.
The primate appears to be the most primitive known relative of the group that contains tarsiers
, small primates found only in Southeast Asia. The finding suggests this group diverged from anthropoids, the group that contains monkeys, apes and humans, during the Eocene epoch (55.8 million to 33.9 million years ago), a time of widespread warming.
It's not the oldest primate fossil, researchers say, but it is one of the oldest most-complete skeletons of the group known as tarsiiformes.
"This discovery is really exciting," vertebrate paleontologist Jonathan Bloch of the University of Florida's museum of natural history told LiveScience, "because it shows us the first really [well-articulated] skeleton of one branch of the crown primate tree
," (the group including all primates alive today and their common ancestor). Bloch was not involved in the study.
The fossil confirms speculation that the earliest primates probably lived in trees, ate insects and were active during the daytime.
The primate, now named Archicebus achilles
(roughly translated as "ancient monkey"), would have weighed about 1 ounce (20-30 grams), suggesting the earliest primates were very small.
The skeleton shares some features of tarsiers and some of anthropoids. For instance, the specimen's heel bone strongly resembles those of anthropoids, hence the species name, achilles.