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Seymouriamorph

Seymouriamorpha
Temporal range: Early Permian - Late Permian
Seymouria1.jpg
Skeleton of Seymouria in the National Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Reptiliomorpha
Order: Seymouriamorpha
Watson, 1917
Subgroups

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See text.

Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered reptiliomorphs, and most paleontologists may 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. The adults were terrestrial. They ranged from lizard-sized creatures (30 centimeters) to crocodile-sized 150 centimeter long animals. They were reptile-like. 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 Permian.

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

Kotlassia

Utegenia

Seymouria baylorensis

Seymouria sanjuanensis

Ariekanerpeton

Discosauriscus austriacus


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