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).

However, aquatic larvae bearing external gills and grooves from the lateral line system have been found, making them unquestionably non-amniotes.

Seymouriamorphs are divided into three main groups: Kotlassiidae, Discosauriscidae, and Seymouriidae, which includes the best-known genus, Seymouria.

[3] Cladogram based on Ruta, Jeffery, & Coates (2003):[5] Kotlassia Utegenia Seymouria baylorensis Seymouria sanjuanensis Ariekanerpeton Discosauriscus austriacus Discosauriscus pulcherrimus Cladogram based on Klembara (2009) & Klembara (2010):[6][7] Utegenia Seymouria Karpinskiosaurus Makowskia Spinarerpeton Ariekanerpeton Discosauriscus