An ancient fish possessed primitive digits that may have been the precursors to our own fingers and toes, according to a new study.

The finding supports recent studies that suggest primitive fish and sharks had the genes necessary to develop digits, even if the animals didn't grow those appendages. "The contrary position was that the hand and foot was a complete novelty that appeared - out of nowhere - in the first four-legged land animals, called tetrapods”, said study team member Per Ahlberg, a paleontologist at Uppsala University in Sweden. That theory "can now pretty much be dismissed," Ahlberg added.

Using medical X-rays, Alhberg and his team created a three-dimensional image of a fin belonging to Panderichthys, a coastal fish that lived about 385 million years ago during the Devonian period. The scans revealed the ancient fish had many of the same bones that make up a modern human arm, including the humerus, radius, and ulna, as well as four small "radial" bones that look remarkably like rudimentary fingers, the authors said. Unlike human fingers, however, Panderichthys's digits were concealed in the fleshy arm-like base of its fin. With the origin of tetrapods, the outermost part of the fin was lost, allowing the "fingers" that were always present at the base of the fin to emerge, Ahlberg said.

The research was detailed September 21 in the journal Nature. 

Ker Than
for National Geographic News

September 24, 2008