New Tiktaalik fossils

Updated view of Tiktaalik roseae.
Credit:  University of Chicago,
Neil Shubin

In a couple of weeks, students in both my Vertebrate Zoology and Evolution classes will be discussing fossils  that demonstrate major transitions in the history of life.  There are few more signficant than Tiktaalik roseae, the 375 million year old lobe-finned fish first discovered by Neil Shubin and his group and famously described in Shubin's Your Inner Fish.  Tiktaalik has taught us a lot about the movement of vertebrate life from the water to the land, and it's still teaching us.  A new study appearing in the Proceedings of the National Academy of Sciences and summarized here at Science Daily describes new Tiktaalik fossils that suggest that a form of "four-wheel drive", employing the pelvic fins for locomotion began in fish, before vertebrate life had actually moved to land.  It had been previously believed that the fish had relied primarily on the front limbs to drag themselves along - the detail removed in the new fossils suggest otherwise.  They demonstrate a well developed ball-and-socket joint which would have connected to very mobile femur that could be brought underneath the body. The sites of muscle attachment show strength and advanced fin function.  It appears that the hind fin was at least as long and highly developed as the forefin.  This suggests that, while the fin could certainly have been used as a paddle in swimming, it could also have served in walking.