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.

Description and lifestyle
The adults animals reached a body length of ca. 150 cm, and had an elongate trunk and a laterally compressed tail. In some specimens lateral line sulci are retained. These body features suggest an aquatic mode of life, with aquatic larvae that probably breathed with external gills like modern tadpoles, while the adults breathed with lungs. Sclerocephalus underwent significant changes during its ontogeny, for example the eyes are much larger and the tail much longer in larvae than in adults. The latest revision, redescription and phylogenetic study of this genus was provided by Schoch & Witzmann (2009).

Sclerocephalus was often classified within the deprecated paraphyletic taxa Stegocephalia and Labyrinthodontia, because of a skull that was connected to the shoulder girdle and teeth of labyrinthodont type. The skull had a distinct pineal foramen. Besides the usual row of teeth in the upper and lower jaw, Sclerocephalus also had three additional pairs of palatine teeth. From specimens with fossilized stomach content we know the adults mainly fed on fish of the genus Paramblypterus, but sometimes also on other amphibians (Branchiosaurus, Micromelerpeton) and even small conspecifics.

Discovery
The holotype of Sclerocephalus haeuseri was described 1847 by the German paleontologist Georg August Goldfuss, who misidentified the fossil as skull of a fish. The famous American vertebrate paleontologist Alfred Romer recognized in 1939 that the fossil amphibians described as Leptorophus levis are the larvae of Sclerocephalus. The most important modern research on Sclerocephalus was published by Boy (1988) and Schoch (2000, 2002, 2003, 2009).

A famous locality that yielded numerous excellently preserved fossils of Sclerocephalus is Odernheim am Glan in Rhineland-Palatinate (Germany), where the Permian sediments of the Rotliegend have even been named "Stegocephalenkalke" (= Stegocephalia limestones).