Seymouriamorpha

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).

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. 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 are divided into three main groups: Kotlassiidae, Discosauriscidae, and Seymouriidae, which includes the best-known genus, Seymouria. The last seymouriamorphs became extinct by the end of the Permian.

Taxonomy

 * Biarmica
 * Enosuchus
 * Kotlassia
 * Leptoropha
 * Microphon
 * Nyctiboetus
 * Utegenia
 * Waggoneria
 * Family Karpinskiosauridae
 * Karpinskiosaurus
 * Family Discosauriscidae
 * Ariekanerpeton
 * Discosauriscus
 * Makowskia
 * Spinarerpeton
 * Family Seymouriidae
 * Seymouria

Cladogram based on Ruta, Jeffery, & Coates (2003):

Cladogram based on Klembara (2009) & Klembara (2010):