Fossils Reveal Link Between Fish and Walking Animals

By Michele Berger
Published: January 14, 2014

A close up view of the hip bone of Tiktaalik roseae. New research reveals this species may show the transition from fins to legs. (University of Chicago, Kevin Jiang)

Newly discovered fossils reveal that in the move from swimming animals to those that walked, there may have been a middle phase, one with enhanced fins, according to research published yesterday.

Researchers from the University of Chicago, Drexel University and Harvard University looked at pelvic bones and determined that a 375-million-year-old species called Tiktaalik roseae had enhanced hind fins. They’re calling it the “best-known” transitional link between fish and legged animals to date.

To describe Tiktaalik means drawing upon animals we know today: fish, eels, crocodiles and alligators. But really, the animal looks something like a combination of several — what you might expect given its now-determined role as middleman. What we do know is that it had sharp teeth, gills, scales and fins, according to a University of Chicago news release. In addition, “its large forefins had shoulders, elbows and partial wrists, which allowed it to support itself on ground.”

An updated illustration of Tiktaalik roseae in its natural environment. (University of Chicago, Neil Shubin)

Tiktaalik is like a poster child of an animal that has mosaic features,” Ted Daeschler of Philadelphia’s Academy of Natural Sciences and one of the paper authors, told The Washington Post.

It still took some 10 million years after this species for real four-limbed animals to emerge, The Post adds.

Despite the mystery surrounding why this transition to land walkers happened, Tiktaalik nonetheless answers some questions. “It’s what we’ve all been waiting for,” Jennifer Clack, of the University of Cambridge’s Museum of Zoology, told The Boston Globe. (Clack was not involved in the research.) “Until this discovery, we weren’t able to see the changes by which the pelvic fins of the fish became much larger and more robust, and gradually turned into the tetrapod hind limb.”

The research was published online January 13 in the Proceedings of the National Academy of Sciences

MORE: Amazing Images of Underwater Creatures

Russian photographer Alexander Semenov captures a close-up image of an unidentified starfish. (Alexander Semenov)

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