Dvinosaurs are one of several new clades of Temnospondyl amphibians named in the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

review of the group by Yates and Warren 2000. They represent a group of primitive semi-aquatic to completely aquatic amphibians, and are known from the Late Carboniferous to the Early Triassic, being most common in 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 Pale ...

period. Their distinguishing characteristics are a reduction of the otic notch; the loss of a flange on the rear side of the pterygoid; and 28 or more presacral vertebrae. Trimerorhachidae is the most

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

family of dvinosaurs. Most other dvinosaurs are placed in the superfamily

Dvinosauroidea Dvinosauroidea is a superfamily of dvinosaurian temnospondyls that lived during the Late Carboniferous period. Gallery Isodectes obtusus.jpg, '' Isodectes obtusus'', an eobrachyopid of the early Permian 01 or '01 may refer to: * The year 20 ...

. Within Dvinosauroidea are two families, Eobrachyopidae and

Tupilakosauridae Tupilakosauridae is an extinct family of dvinosaurian temnospondyls. It contains the genera '' Slaugenhopia'', '' Thabanchuia'', '' Tupilakosaurus'', and possibly '' Kourerpeton''. Tupilakosaurs are known from Texas, Greenland, Russia, and Fran ...

, as well as dvinosaurs that cannot be placed in either family, such as '' Dvinosaurus'' and '' Kourerpeton''. A 2008 phylogenetic analysis found Eobrachyopidae to be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, representing a grade of basal dvinosauroids. Below is a

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 ...

showing the phylogenetic relationships of dvinosaurs from Englehorn ''et al.'' (2008):

References

* Laurin, M. and Steyer, J-S (2000
Phylogeny and Apomorphies of Temnospondyls

The 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 h ...

* Yates, A. M., and Warren A. A., 2000, The phylogeny of the ‘higher’ temnospondyls (Vertebrata: Choanata) and its implications for the monophly and origins of the Stereospondyli: '' Zoological Journal of the Linnean Society'', v. 128, p. 77-121.

External links

Temnospondyli: Limnarchia
at Palaeos

at Mikko's Phylogeny Archive (cladogram based on Yates and Warren 2000)
Suborder †Dvinosauria
- Scientific Hierarchy at the Taxonomicon Carboniferous temnospondyls Permian temnospondyls Triassic temnospondyls Carboniferous amphibians of North America Permian amphibians of North America Triassic amphibians of North America Permian Kansas Permian geology of Nebraska Prehistoric animal suborders Amphibian suborders {{temnospondyli-stub