''Gephyrostegus'' is an

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 ...

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 ...

of gephyrostegid

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 de ...

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

. It was a small animal, 22 cm in total length, of generally lizard-like build and presumably habit. It had large eyes and a large number of small, pointed teeth, indicating it was an active

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

hunter. The remains have been found in

Nýřany Nýřany (; german: Nürschan) is a town in Plzeň-North District in the Plzeň Region of the Czech Republic. It has about 6,900 inhabitants. Administrative parts Villages of Doubrava and Kamenný Újezd are administrative parts of Nýřany. Geo ...

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

, dating from around 310 million years ago (upper

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

). Originally thought to have been a

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 of view, but some analyses suggest that seymouriamorphs are s ...

, the phylogenetic position is uncertain, and now it belongs to the family

Gephyrostegidae Gephyrostegidae is an extinct family of reptiliomorph tetrapods from the Late Carboniferous including the genera '' Gephyrostegus'', '' Bruktererpeton'', and '' Eusauropleura''. ''Gephyrostegus'' is from the Czech Republic, ''Brukterepeton'' is f ...

, together with the genus ''

Bruktererpeton ''Bruktererpeton'' is an extinct genus of gephyrostegid reptiliomorph known from the Late Carboniferous of the Rhein-Ruhr-District, western Germany. It was first described and named by Jürgen A. Boy and Klaus Bandel in 1973 and the type specie ...

''. Several phylogenetic studies indicate that ''Gephyrostegus'' is only distantly related to

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, more distantly than

diadectomorphs Diadectomorpha is a clade of large tetrapods that lived in Euramerica during the Carboniferous and Early Permian periods and in Asia during Late Permian (Wuchiapingian), They have typically been classified as advanced reptiliomorphs (transiti ...

, lepospondyls and seymouriamorphs were. At 22 cm snout-vent length, ''Gephyrostegus'' is one of the smallest (if not ''the'' smallest) advanced reptiliomorphs found. The type species is ''Gephyrostegus bohemicus'', the type of which is the specimen with its skull and scattered elements of the anterior postcranial skeleton preserved; another known specimen is an articulated postcranial skeleton, lacking only the tail and a few phalanges. Brough and Brough (1967) erected the species ''Gephyrostegus watsoni'' for a smaller, possibly juvenile individual, previously considered to be an individual of ''

Diplovertebron ''Diplovertebron'' (from el, διπλοῦς , 'double' and la, vertebron, 'vertebra') is an extinct genus of embolomere that lived in the Late Carboniferous period ( Moscovian), about 310 million years ago. ''Diplovertebron'' was a medium-s ...

punctatum''.Brough, M.C. and Brough J. (1967): The Genus ''Gephyrostegus''. ''

Philosophical Transactions of the Royal Society of London ''Philosophical Transactions of the Royal Society'' is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It was established in 1665, making it the first journa ...

''. Series B, Biological Sciences no 252 (776): pp. 147–165. Carroll (1970, 1972) considered the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

of ''Gephyrostegus watsoni'' to be a skeleton of an immature individual of ''G. bohemicus''.Robert L. Carroll "Gephyrostegida, Solenodonsauridae" pp. 1-19 ''in'': Robert L. Carroll, Oskar Kuhn and L. P. Tatarinov (1972) ''Handbuch der Paläoherpetologie - Encyclopedia of Paleoherpetology Part 5B - Batrachosauria (Anthracosauria) Gephyrostegida – Chroniosuchida'' Gustav Fischer Verlag - Stuttgart & Portland, 81 pp.,
web page
/ref> The skeleton of the smaller individual has few of the features characterizing the skeletons of larvae of discosauriscid seymouriamorphs, and its morphology is overall very similar to that of adult specimens. Carroll (1970, 1972) states that while the skeleton of ''Gephyrostegus'' shows some adaptations for terrestrial life (e.g. in the specialization of the tarsus), it also retained some traits characteristic to aquatic non-amniote tetrapods, such the large size of the skull and the loose attachment of the vertebral elements, making it overall not as well adapted to the terrestrial environment as amniotes are. According to Carroll, ''Gephyrostegus'' probably spent a large proportion of its adult life on land, but it may be assumed that it retained aquatic reproductive habits. Brough and Brough (1967) considered ''

Solenodonsaurus ''Solenodonsaurus'' ("single-tooth lizard") is an extinct genus of reptiliomorphs that lived in what is now Czech Republic, during the Westphalian stage. Description ''Solenondosaurus'' had snout-vent length with a skull length . ''Solenodo ...

'' to be a junior synonym of ''Gephyrostegus'', but other authors consider them to be a separate genera. Some specimens classified by Brough and Brough (1967) as individuals of ''Gephyrostegus bohemicus'' were subsequently recognized as basal

eureptilia Eureptilia ("true reptiles") is one of the two major subgroups of the clade Sauropsida, the other one being Parareptilia. Eureptilia includes Diapsida (the clade containing all modern reptiles and birds), as well as a number of primitive Perm ...

ns; their "specimen I" became a holotype of '' Brouffia orientalis'', while "specimen II" became a holotype of ''

Coelostegus ''Coelostegus'' is an extinct genus of Late Carboniferous (late Westphalian stage) basal reptile known from Pilsen of Czech Republic. It is known from the holotype ČGH 3027, a partial skeleton of an immature individual. It was collect ...

prothales''.

References

{{Taxonbar, from=Q21032545 Carboniferous tetrapods of Europe Reptiliomorphs Transitional fossils