Missing Links and Found Links: Enter the Fishapod
In and out of the water, transitional forms from the fossil record illuminate the nuts and bolts of evolution
by Pat Shipman
I am equally enamored of another found link, the fossil skeleton of Tiktaalik roseae, described on April 6, 2006, in the journal Nature. Tiktaalikis a name suggested by the elders of the Nunavut people, who live where the fossils were found on Ellesmere Island in the Canadian Arctic; it means “large, shallow-water fish.” This 375-million-year-old fish shows a delicious combination of unexpected features, some inherited from its fishy ancestors and some typical of later land-dwelling tetrapods (four-footed animals). Neil Shubin of the University of Chicago, co-leader of the discovery team, jokingly calls the newly discovered species a “fishapod.”
Tiktaalik’s fins, gills, scales and primitive jaw show it was a fish. Unlike fish and like tetrapods, it had a distinct neck, so its head moved independently of its body. Its flattened head and broad body make Tiktaalik look somewhat like a weird, scaly crocodile, an impression enhanced by its four-to-nine-foot length. Its skeleton differs markedly from those of crocodiles or alligators, though, despite the overall resemblance in body shape. Tiktaalik’s front fins hold the biggest surprise. Each was a sort of half-fin, half-leg containing the bony elements found in a limb—with a functional wrist, elbow and shoulder—and yet retaining the bony “rays” of a fish fin. According to team member Farish Jenkins, Jr., of Harvard University, the front fins were sturdy enough to support the creature in very shallow water or on land for brief trips…
(read more: American Scientist)
(images: T - Ted Daeschler/VIREO; B - Kalliopi Monoyios)
