Amphibamus lyelli (Cope 1865) Late Carboniferous, ~310 mya, ~15 cm in length, was derived from a sister to Utegenia and phylogenetically precededDendrerpeton and Cacops.
Distinct from Utegenia, the intertemporal fused to the postfrontal. The vomers were broad with lateral palatine processes. The pterygoids were narrower and more widely separated.
Only 18 presacral vertebrae were present, all with short straight ribs.
The scapulocoracoid was narrower. The forelimb was gracile. The hand was longer than the ulna. Only four fingers (1-4) were present.
The pelvis extended anteriorly as a plate separate from the ischium. The hindlimb was larger than the forelimb, but equally gracile. Metatarsals 3 and 4 were longer than the others.
An eardrum filled the posterior skull. Together these traits indicate adaptations to locomotion over land. Even so, aquatic tadpoles are known.