Seymouriamorpha

Seymouriamorpha are an extinct group of tetrapods (terrestrial vertebrates) known from the Carboniferous and Permian periods. 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). 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.

Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line belonging to the seymouriamorph family Discosauriscidae have been found, making seymouriamorphs unquestionably non-amniotes. 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.

They have been considered to be the makers of the trace fossils placed in the ichnogenusAmphisauropus.