NSF, the independent federal agency that supports fundamental research and education across all fields of science and engineering, funded the research.

The bone’s structure reveals an animal that had powerful forelimbs, with extensive areas for the attachment of muscles at the shoulder. “The size and extent of these muscles means that the humerus played a significant role in the support and movement of the animal,” reported Shubin. “These muscles would have been important in propping the body up and pushing it off of the ground.”

Interestingly, modern-day fish have smaller versions of the muscles. According to Coates, “When this humerus is compared to those of closely-related fish, it becomes clear that the ability to prop the body is more ancient than we previously thought. This means that many of the features we thought evolved to allow for life on land originally evolved in fish living in aquatic ecosystems.”

The layered rock along the Clinton County, Penn., roadside were deposited by ancient stream systems that flowed during the Devonian Period, about 365 million years ago. Enclosed in the rocks is fossil evidence of an ecosystem teeming with plant and animal life. “We found a number of interesting fossils at the site,” reported Daeschler, who uncovered the fossil in 1993. “But the significance of this specimen went unnoticed for several years because only a small portion of the bone was exposed and most of it lay encased in a brick-sized piece of red sandstone.”

Not until three years ago, when Fred Mullison, the fossil preparator at the Academy of Natural Sciences, excavated the bone from the rock, did the importance of the new specimen become evident.

The work was also funded by a grant from the National Geographic Society.