Kotlassia prima (Amalitzky 1898) Late Permian ~275 mya, 1 m in length, was more salamander-like than its sister, Seymouria with a smaller skull, shorter legs and longer torso. Both were derived from a sister to Eoherpeton and Proterogyrinus, and both phylogenetically preceded Silvanerpeton.
Distinct from Seymouria, the skull of Kotlassia was relatively smaller and flatter. The stapes was slender, presumeably for improved hearing. The rostrum was shorter and the orbits were more dorsally directed.
24-28 presacral vertebrae were present. Two sacral vertebrae were present, as in reptiles. The pectoral ribs were expanded at their tips.
The limbs were all relatively smaller, suggesting a more aquatic lifestyle. Only four digits are known for the foot.
Tadpoles are known for closely related taxa.
A reptilomorph family tree is here. A more complete family tree of the Reptilia and their ancestors is here.