Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest that seymouriamorphs are stem-tetrapods (not more closely related to Amniota than to Lissamphibia).[2] Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line system have been found, making them unquestionably amphibians. Though as they matured, they became more terrestrial and reptile-like. They ranged from 30 cm (1 ft) long lizard-sized creatures to the 1.5 m (5 ft) long Enosuchus. If seymouriamorphs are reptiliomorphs, they were the distant relatives of amniotes. Seymouriamorphs form into three main groups, Kotlassiidae, Discosauriscidae, and Seymouriidae, a group that includes the best known genus, Seymouria. The last seymouriamorph became extinct by the end of the Permian.[3]
^Klembara, Jozef (2009). "The skeletal anatomy and relationships of a new discosauriscid seymouriamorph from the lower Permian of Moravia (Czech Republic)". Annals of Carnegie Museum. 77 (4): 451–483. doi:10.2992/0097-4463-77.4.451.