Seymouriamorpha were a small but widespread group of limbed vertebrates (

tetrapods A tetrapod (; from Ancient Greek τετρα- ''(tetra-)'' 'four' and πούς ''(poús)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the lat ...

). They have long been considered

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

s (

reptiliomorph 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 ...

s), 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 The Lissamphibia (from Greek λισσός (lissós, "smooth") + ἀμφίβια (amphíbia), meaning "smooth amphibians") is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia ( ...

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

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e bearing external

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

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 epithelia ...

system have been found, making them unquestionably non-amniotes. As they matured, they became more terrestrial and

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

-like. They ranged from 30 cm (1 ft) long

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

-sized creatures to the 1.5 m (5 ft) long ''

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 i ...

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

s. Seymouriamorphs are divided into three main groups: Kotlassiidae,

Discosauriscidae Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem group, stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest th ...

, and Seymouriidae, which includes the best-known genus, ''

Seymouria ''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 ma ...

''. The last seymouriamorphs became

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

by the end of the

Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...

. They have been considered to be the makers of the

trace fossil A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

s placed in the

ichnogenus An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxon'' comes from the Ancient Greek (''íchnos'') meaning "track" and English , itself derived from ...

Amphisauropus ''Amphisauropus'' is an ichnogenus commonly found in assemblages of trace fossils dating from the Permian to the Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end ...

''.

Taxonomy

*'' Biarmica'' *''

'' *''

Kotlassia ''Kotlassia'' (meaning "of Kotlas") extinct genus of kotlassiine seymouriamorph from the Late Permian of Russia. The type, and currently only, species is ''K. prima''. Discovery and naming During the 1890s, Russian paleontologist Vladimir A ...

'' *''

Leptoropha ''Leptoropha'' is an extinct genus of aquatic seymouriamorph known from the Middle Permian of Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by ...

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

Utegenia ''Utegenia'' is a genus of early tetrapod. It is usually regarded as a basal seymouriamorph, but sometimes included in the Discosauriscidae or as a sister taxon of the latter. Only one species, ''Utegenia shpinari'', found from Kazakhstan, is ...

'' *''

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 t ...

'' *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 stem-amniotes (reptiliomorphs), and most paleontologists still accep ...

'' *Family Discosauriscidae **'' Ariekanerpeton'' **''

Discosauriscus ''Discosauriscus'' was a small seymouriamorph which lived in what is now Central and Western Europe during the latest Carboniferous and in the Early Permian Period. Its best fossils have been found in the Broumov and Bačov Formations of Bosko ...

'' **'' Makowskia'' **'' Spinarerpeton'' *Family Seymouriidae **''

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

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 (ToL) 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 s ...

{{Taxonbar, from=Q134777 Pennsylvanian first appearances Lopingian extinctions Prehistoric tetrapod orders