And Now for Something Uniquely Humerus

A 365-million-year-old arm bone fossil found in Pennsylvania came from one of the first creatures able to do push-ups, an evolutionary step that was necessary for animals to move from the sea to dry land. When the animal lived, there were no vertebrates on dry land and the oceans were a place of fierce, toothy meat eaters.

The 2-foot-long, four-legged creature is the earliest known specimen to have a humerus, or upper arm bone, according to Neil Shubin of the University of Chicago. Such a bone, far different from the flipper bones of fish, gave the creature an important new ability -- it could raise its upper body like an athlete doing push-ups.