The gaps keep getting smaller and smaller

As we all know, Tiktaalik roseae is a magnificent example of a transitional fossil connecting aquatic critters–fish–with tetrapods, 4-limbed critters. Nevertheless, there are still gaps in that transitional sequence. A recent PNAS paper (link to abstract; full paper is behind a paywall) describes fossils of early amphibians that are later than Tiktaalik and are within Romer’s Gap. Romer’s Gap is a period around 15 million years long, from roughly 360mya to 345mya, where (up to now) there was a distinct lack of fossils of proto-tetrapods or related critters. The new PNAS paper’s senior author is Jenny Clack, one of the most prominent paleontologists studying that era, (along with people like Neal Shubin and Per Ahlberg. Per was an active commenter on the late lamented Internet Infidels Discussion Board way back when I was an administrator of IIDB.

With these new fossils, the transition from water to land animals is becoming nearly as well documented as the synapsid to mammal transition. Nobel Intent has more on the new paper.