Sclerocephalus

Sclerocephalus is an extinct genus of temnospondyl amphibian from the lowermost Permian of Germany with four valid species, including the type species S. haeuseri. It is one of the most completely preserved and most abundant Palaeozoic tetrapods. Sclerocephalus was once thought to be closely related to eryopoid temnospondyls, but it is now thought to be more closely related to archegosauroids. It is the only genus in the family Sclerocephalidae.

Read more about Sclerocephalus:  Description and Lifestyle, Discovery, Taxonomy, Phylogeny