Amphibian August #03 – Crassigyrinus

Often described as a “giant carnivorous tadpole”, Crassigyrinus lived during the Early Carboniferous of Scotland (~345-328 mya), with a possible specimen also found in West Virginia. It’s one of the few early tetrapods known from “Romer’s Gap”, a period of time during the group’s evolution which is frustratingly lacking in fossils.

Crassigyrinus showed the earliest known example of five-digit pentadactyl limbs, a characteristic ancestral to all living tetrapods. Its forelimbs were proportionally tiny compared to its 2m long body (6′6″), and its pelvis lacked a solid connection to its spine, suggesting it was actually an entirely aquatic animal – possibly representing the first group of tetrapods who gave up on the whole “land” business and returned full-time to the water.

Distinctive surface ornamentation on parts of its skull have also led to some speculation that it might have had weed-mimicking skin fringes, similar to modern matamata turtles and wobbegongs.