Meet the Oldest Primate on Record Yet

Say hello to one of your oldest ancestors: Scientists have discovered and pieced together a nearly complete skeleton from the oldest primate ever discovered, a 55 million year-old, monkey-like creature that weighed just an ounce.

Archicebus achilles, named for the Greek with the famous heel, was discovered more than 10 years ago in China's Hubei Province, near where the Yangtze River runs today. The area is a hotbed for paleontological discoveries because it was once a lush tropical forest. Archicebus is more than 7 million years older than the next oldest primate ever discovered. A rodent-like creature called Purgatorious that was discovered in Montana is believed to be 65 million years old, but researchers are split on whether the animal was a true primate. The discovery has scientists more convinced that primates originated in Asia, not Africa as previously suspected.

"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 Dan Gebo, a researcher at Northern Illinois University and a coauthor of the study published Wednesday in Nature.

Archicebus is smaller than today's smallest primate, Madagascar's pygmy mouse lemurs, throwing another wrench in paleontologists' belief that the earliest primates were similar in size to modern monkeys. Archicebus had a long tail, was likely active in the daytime (today's tarsiers are nocturnal), and most likely hunted insects.

According to Christopher Beard, a paleontologist at the Carnegie Museum of Natural History, the find is an important one because Archicebus has traits of both modern anthropoids (humans, apes, chimps) and modern tarsiers, providing the potential missing link between those evolutionary branches.

"Archicebus differs radically from any other primate, living or fossil, known to science," Beard said. "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. It will force us to rewrite how the anthropoid lineage evolved."

Scientists are most interested in the little guy's foot (hence the name) because it's got a monkey-like heel, but the primitive toes of tree-dwelling primates.

"We see typical robust grasping big toes, long toes and nailed digits of primitive arboreal primates, but we also have rather monkey-looking heel bones and monkey-like long metatarsals, often viewed as advanced features that you would not normally find in a primitive early Eocene fossil primate," Gebo said. "We have interpreted this new combination of features as evidence that this fossil is quite primitive and its unique anatomical combination is a link between the tarsier and monkey-ape branches of dry-nosed primates."