Fossilized coelacanth fin reveals evolutionary secret

An icon of cryptozoology, the coelecanth is a fish that was thought to have been extinct for 65 million years ago until it was found alive in 1938. Now, another mystery surrounding the fish has been solved. Scientists have long wondered why the coelecanth's fins are symmetrical while land animals like us that shared a common ancestor with the fish have asymmetrical hands and feet. If hands and feet evolved from asymmetric fins, it should follow that the colecanth's fins would also be asymmetric. Recently, University of Chicago grad student Matt Friedman found the missing piece of the puzzle, the only fossil ever discovered of an ancestral coelacanth's fin. It's the cover story in the current issue of the journal Evolution & Development.

From New Scientist:

Recent fossil discoveries have shown that hands and feet evolved from an extinct ancestral fish with asymmetric fins, but the question of how the coelacanth got its symmetrical fins remained....

The fossil (that Friedman found) revealed that the ancestor, which the researchers have named Shoshonia arctopteryx, had asymmetric fins. This indicates that the living coelacanth evolved its symmetry.

That Shoshonia and living coelacanths are different is perhaps not entirely surprising – coelacanths have, after all, been evolving for 400 million years. But it serves as a lesson to those studying limb development.

"The asymmetry in our own paired limbs is in fact a primitive feature," says Michael Coates of the University of Chicago, US. While the coelacanth has not retained this feature, other, more primitive living fish have.

Link to New Scientist, Link to abstract of Evolution & Development paper, Link to University of Chicago press release

Previously on BB:
• Coelacanth in danger Link
• Coelacanth caught on video Link
• Video: Indonesian coelacanth Link
• Fisherman catches coelacanth Link