New fossil weighs in on primate origins

Excavations in Wyoming have yielded the partial skeleton of a 55-million-year-old primate that probably was a close relative of the ancestor of modern monkeys, apes, and people. The creature was built for hanging tightly onto tree branches, not for leaping from tree to tree, as some scientists had speculated, based on earlier fragmentary finds. Also, despite expectations, the ancient primate didn’t have eyes specialized for spotting insects and other prey.

Jonathan I. Bloch and Doug M. Boyer, both of the University of Michigan in Ann Arbor, unearthed the new specimen. It belonged to a group of small, long-tailed primates that lived just before the evolution of creatures with traits characteristic of modern primates–relatively large brains, grasping hands and feet with nails instead of claws, forward-facing eyes to enhance vision, and limbs capable of prodigious leaping.

The new find, in the genus Carpolestes, had long hands and feet with opposable digits, Bloch and Boyer report in the Nov. 22 Science. The animal grew nails on its opposable digits, and claws on its other fingers and toes. Unlike later primates, Carpolestes had side-facing eyes and lacked hind limbs designed for leaping.

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