Seymouriamorpha were a small but widespread group of limbed vertebrates ( tetrapods). They have long been considered

reptiliomorphs Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...

, 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 The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), ...

). Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e bearing external

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s and grooves from the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

system have been found, making them unquestionably amphibians. The adults were terrestrial. They ranged from

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

-sized creatures (30 centimeters) to

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

-sized 150 centimeter long animals. They were

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

-like. If seymouriamorphs are reptiliomorphs, they were the distant relatives of

amniote Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are disti ...

s. Seymouriamorphs form into three main groups, Kotlassiidae,

Discosauriscidae Discosauriscidae is a family of stegocephalians from the early Permian. They belong to the Seymouriamorpha, but their affinites to extant tetrapods are debated. They have long been considered reptiliomorph Reptiliomorpha (meaning reptile-shap ...

, and

Seymouriidae ''Seymouria'' is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. Although they were amphibians (in a biological sense), ''Seymouria'' were well-adapted to life on land, with many reptilian features—so man ...

, a group that includes the best known

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

, '' Seymouria''. The last seymouriamorph became

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

by the end of the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

Taxonomy

* Reptiliomorpha *Order Seymouriamorpha **'' Biarmica'' **'' Enosuchus'' **''

Kotlassia ''Kotlassia'' is an extinct genus of seymouriamorph. Fossils of it are found in Russia, in the village of Novinki, close to the city of Kotlas. The name of the genus is derived from the city. The layers in which the fossils were found date from ...

'' **''

Leptoropha ''Leptoropha'' is an extinct genus of aquatic seymouriamorph known from the Middle Permian of Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the larges ...

'' **'' Microphon'' **'' Nyctiboetus'' **''

Utegenia ''Utegenia'' is a genus of early tetrapod. It is usually regarded as a Basal (phylogenetics), basal Seymouriamorpha, seymouriamorph, but sometimes included in the Discosauriscidae or as a sister taxon of the latter. Only one species, ''Utegenia ...

'' **''

Waggoneria ''Waggoneria'' is a genus of seymouriamorph from the Early Permian of Texas. It was named by American paleontologist Everett C. Olson in 1951 on the basis of a holotype fossil that included a weathered skull, lower jaws, vertebrae, and part of ...

'' **Family

Karpinskiosauridae ''Karpinskiosaurus'' is an extinct genus of seymouriamorphs. It includes two species: ''Karpinskiosaurus secundus'' and ''Karpinskiosaurus ultimus''. ''Karpinskiosaurus secundus'' is represented by two specimens with skull lengths of about 75&nbs ...

***'' Karpinskiosaurus'' **Family

***''

Ariekanerpeton ''Ariekanerpeton'' is an extinct genus of seymouriamorph from the lower Permian. Fossils have been found from Tajikistan representing over 900 individuals of various stages of ontogenic development. However, it is thought that none of these spec ...

'' ***''

Discosauriscus ''Discosauriscus'' was a small seymouriamorph which lived in what is now Central and Western Europe in the Early Permian Period. Its best fossils have been found in the Broumov and Bačov Formations of Boskovice Furrow, in the Czech Republic. ...

'' ***''

Makowskia ''Makowskia'' is an extinct genus of discosauriscid seymouriamorph known from the early Permian (lower Saxonian age) of Boskovice Furrow, in the Czech Republic. It was first named by Jozef Klembara in 2005 and the type species is ''Makowskia l ...

'' ***''

Spinarerpeton ''Spinarerpeton'' is an extinct genus of discosauriscid seymouriamorph known from the early Permian of Boskovice Furrow, in the Czech Republic. It was first named by Jozef Klembara in 2009 and the type species is ''Spinarerpeton brevicephalum'' ...

'' **Family

***'' Seymouria'' Cladogram based on Ruta, Jeffery, & Coates (2003): Cladogram based on Klembara (2009) & Klembara (2010):

Gallery

File:Kotlassia prima1DB.jpg, ''

'' File:Karpinskiosaurus1DB.jpg, '' Karpinskiosaurus''

References

External links

Bystrow, A.P. ''Kotlassia prima'' Amalitzky. Bulletin of the Geological Society of America, Washington, 1944, v.55, N5, pp.379-416.

- at Paleos
Seymouriamorpha
at Tree of Life Web Project Seymouriamorphs Cisuralian first appearances Lopingian extinctions {{permian-animal-stub