University of Alberta Assistant Professor Pierre Lemelin and a team of U.S. researchers made the discovery in 2,000-year-old bones found in 2003 in a cave in southeastern Madagascar.

A lemur is a monkey-like animal with a long tail and large eyes.

An examination of the five tiny hand bones revealed a never-before-seen hand joint configuration on the side of the little finger, Lemelin said. The same joint configuration is straight in all other primates.

"Our analysis showed a mosaic of lemurid-like, monkey-like and very unique morphological traits," Lemelin said. "Because the joint was present on both hands, it's likely not an anomaly, but because there are no other Hadropithecus hand bones for comparison, we don't know for certain," Lemelin said.

"It is a mystery, and further investigation is needed to explain the difference in this species," he added.

Lemelin and his U.S. colleagues from George Washington University, the Medical College of Georgia and the universities of Stony Brook and Massachusetts-Amherst report their discovery in the Journal of Human Evolution.