Dvinosaurs are one of several new clades of

Temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carbo ...

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 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 251.9 Mya. It is the last ...

period. Their distinguishing characteristics are a reduction of the

otic notch Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Otic notches are one of the features lost in the evolution of amniotes from their tetrapod ancestors. The notches have been interpreted as part of a ...

; the loss of a flange on the rear side of the

pterygoid Pterygoid, from the Greek for 'winglike', may refer to: * Pterygoid bone, a bone of the palate of many vertebrates * Pterygoid processes of the sphenoid bone ** Lateral pterygoid plate ** Medial pterygoid plate * Lateral pterygoid muscle * Medi ...

; and 28 or more presacral vertebrae.

Trimerorhachidae Trimerorhachidae is a family of dvinosaurian temnospondyls, including Trimerorhachis and Neldasaurus. They are vertebrates and carnivores. Gallery Trimerorhachis insignis life restoration.jpg, '' Trimerorhachis insignis'', of the early Perm ...

is the most basal family of dvinosaurs. Most other dvinosaurs are placed in the superfamily Dvinosauroidea. Within Dvinosauroidea are two families,

Eobrachyopidae Eobrachyopidae is a family of dvinosaurian temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primi ...

and Tupilakosauridae, as well as dvinosaurs that cannot be placed in either family, such as '' Dvinosaurus'' and ''

Kourerpeton ''Kourerpeton'' is an extinct genus of dvinosaurian temnospondyl. Fossils of ''Kourerpeton'' were discovered in a window of a barber's shop in either Bisbee or Mesa, Arizona. ''Kourerpeton'' was named in 1976, with the type and only species be ...

''. A 2008 phylogenetic analysis found Eobrachyopidae to be paraphyletic, 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 * 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 The ''Zoological Journal of the Linnean Society'' is a monthly peer-reviewed scientific journal covering zoology published by Oxford University Press on behalf of the Linnean Society. The editor-in-chief is Maarten Christenhusz (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