The first handbones of Hadropithecus. Photo by Dr. Pierre Lemelin, U. of Alberta.
From the press release:
Analysis of the first hand bones belonging to an ancient lemur has revealed a mysterious joint structure that has scientists puzzled.Researchers analyzed the first hand bones ever found of Hadropithecus stenognathus, a lemur that lived 2,000 years ago. The bones were discovered in 2003 in a cave in southeastern Madagascar, an island nation off the coast of Africa in the Indian Ocean. Hadropithecus is related to the modern-day sifaka, a type of lemur with acrobatic leaping skills.
Examination revealed a never-before-seen hand joint configuration on the side of the little finger. The same joint configuration is straight in all other primates, including Archaeolemur, a close extinct relative of Hadropithecus. The hand bones also showed that Hadropithecus had very short thumbs and was a quadrupedal species, walking on all fours, much like many primates, such as baboons, do today.
“Our analysis showed a mosaic of lemurid-like, monkey-like and very unique morphological traits,” Lemelin said. Hadropithecus also lacked anatomical traits linked with wrist mobility and strong finger flexion that characterize primate species that climb or cling to trees.