''Deltaherpeton'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of colosteid from middle Mississippian (late

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follow ...

age) deposits of

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D ( NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also ...

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to th ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. It was first named by John R. Bolt and R. Eric Lombard in 2010 and the type species is ''Deltaherpeton hiemstrae''. ''Deltaherpeton'' can be differentiated from other colosteids due to possessing several unique bones along the midline of the skull, separating paired skull bones which typically contact each other along the midline. These include an internasal, an oval-shaped bone which lies at the intersection of the paired

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

e and nasal bones at the top of the snout. Internasals are known from several of the earliest four-limbed vertebrates, such as ''

Acanthostega ''Acanthostega'' (meaning "spiny roof") is an extinct genus of stem-tetrapod, among the first vertebrate animals to have recognizable limbs. It appeared in the late Devonian period (Famennian age) about 365 million years ago, and was anatomic ...

'', '' Ichthyostega'', and baphetids. Further back, what seems to be a pair of

lozenge Lozenge or losange may refer to: * Lozenge (shape), a type of rhombus *Throat lozenge, a tablet intended to be dissolved slowly in the mouth to suppress throat ailments *Lozenge (heraldry), a diamond-shaped object that can be placed on the field of ...

-shape bones lie at the intersection of the nasal bones and frontal bones. These bones may be interfrontonasals, which have been found in some eryopoids and microsaurs. In addition, ''Deltaherpeton'' has a single

postparietal Postparietals are cranial bones present in fish and many tetrapods. Although initially a pair of bones, many lineages possess postparietals which were fused into a single bone. The postparietals were dermal bones situated along the midline of the ...

(rather than a pair), which separates the left and right

supratemporal The supratemporal bone is a paired cranial bone present in many tetrapods and tetrapodomorph fish. It is part of the temporal region (the portion of the skull roof behind the eyes), usually lying medial (inwards) relative to the squamosal and latera ...

and

tabular Table may refer to: * Table (furniture), a piece of furniture with a flat surface and one or more legs * Table (landform), a flat area of land * Table (information), a data arrangement with rows and columns * Table (database), how the table data ...

bones at the rear edge of the skull. Lone postparietals are rare among non-amniote tetrapods and tetrapod relatives; only ''Ichthyostega'' and

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 ...

are known to possess them. The discovery of ''Deltaherpeton'' prompted a review and re-augmentation of the defining characteristics for the family

Colosteidae Colosteidae is a family of stegocephalians (tetrapod-like vertebrates) that lived in the Carboniferous period. They possessed a variety of characteristics from different tetrapod or stem-tetrapod groups, which made them historically difficult to ...

, though it did not help to clarify the relationship between colosteids and other early

tetrapod 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 t ...

s. Though it is believed that ''Deltaherpeton'' is more derived, the species is thought to have shared its environment with other early four-limbed vertebrates such as '' Whatcheeria'' and '' Siguornea'', approximately 339.4 to 336 million years ago.https://www.dinosaurhome.com/creature-feature-8-whatcheeria-deltae-14925.html

References

Carboniferous tetrapods of North America Mississippian animals Prehistoric tetrapod genera Fossil taxa described in 2010 {{Carboniferous-animal-stub