''Gephyrostegus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 ...

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 ...

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

. It was a small animal at 22 cm snout-vent 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 which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...

hunter. The remains have been found in

Nýřany Nýřany (; ) is a town in Plzeň-North District in the Plzeň Region of the Czech Republic. It has about 7,000 inhabitants. Administrative division Nýřany consists of three municipal parts (in brackets population according to the 2021 census): ...

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

, dating from around 310 million years ago (upper

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

).Jaekel, O. (1902)
''Gephyrostegus bohemicus'', n.g. n.sp.
''Zeitschrift der Deutschen geologischen Gesellschaft'' 54: (Verhandlungen der Gesellschaft): 127–132 Originally thought to have been a

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

, the phylogenetic position is uncertain, and now it is placed in the family Gephyrostegidae, together with the genus '' Bruktererpeton''. Several phylogenetic studies indicate that ''Gephyrostegus'' is only distantly related to

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, more distantly than diadectomorphs,

lepospondyls Lepospondyli is a diverse clade of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minimus''), lepospondyls lived from the Visean stage of the Early Carboniferous to the Earl ...

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 punctatum''. Carroll (1970, 1972) considered the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''Gephyrostegus watsoni'' to be a skeleton of an immature individual of ''G. bohemicus''.Carroll, R.L. "Gephyrostegida, Solenodonsauridae" pp. 1-19 ''in'': Carroll, R.L., Kuhn, O. & Tatarinov, L.P. (1972) ''Handbuch der Paläoherpetologie - Encyclopedia of Paleoherpetology Part 5B - Batrachosauria (Anthracosauria) Gephyrostegida – Chroniosuchida'' Gustav Fischer Verlag - Stuttgart & Portland, 81 pp., 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'' to be a junior synonym of ''Gephyrostegus'', but other authors consider them to be a separate genus. Some specimens classified by Brough and Brough (1967) as individuals of ''Gephyrostegus bohemicus'' were subsequently recognized as basal

eureptilia Sauropsida (Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinos ...

ns; their "specimen I" became a holotype of ''

Brouffia ''Brouffia'' is an extinct genus of Late Carboniferous (late Westphalian stage) basal reptile known from Plzeň of Czech Republic. It is known from a single partial skeleton, the holotype ČGH III B.21.C.587 and MP 451 (part and ...

orientalis'', while "specimen II" became a holotype of ''

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

prothales''.

References

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