Seymouriamorpha were a small but widespread group of limbed vertebrates (

tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...

). 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 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 dis ...

than to Lissamphibia). 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 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 Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...

. 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 ''Seymouria'' is an extinct genus of seymouriamorpha, 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 reptile, re ...

''. 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 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 de ...

*Order Seymouriamorpha **'' Biarmica'' **''

Enosuchus ''Enosuchus'' is an extinct genus of seymouriamorphs from Russia during the Middle Permian The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It ...

'' **''

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'' **''

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 ''Karpinskiosaurus'' is an extinct genus of seymouriamorph 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 ...

'' **Family

***'' Ariekanerpeton'' ***''

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'' ***'' Spinarerpeton'' **Family

***''

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

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

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

Gallery

File:Kotlassia prima1DB.jpg, ''

'' File:Karpinskiosaurus1DB.jpg, ''

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 The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site ...

Seymouriamorphs Cisuralian first appearances Lopingian extinctions {{permian-animal-stub