Derwentiinae

{{Short description|Extinct subfamily of amphibians}} {{Automatic taxobox | fossil_range = [[Permian]] - [[Triassic]] | image = Deltasaurus kimberleyensis.jpg | image_caption = ''Deltasaurus kimberleyensis'' | taxon = Derwentiinae | authority = Dias-da-Silva and Marsicano, [[2011 in paleontology|2011]] | subdivision_ranks = Subgroups | subdivision = [[#Classification|See text]] }}

'''Derwentiinae''' is a [[subfamily (biology)|subfamily]] of [[rhytidosteid]] [[temnospondyl]]s from the [[Permian]] and [[Triassic]] periods of [[Australia]] and [[India]]. It includes the genera ''[[Arcadia (genus)|Arcadia]]'', ''[[Deltasaurus]]'', ''[[Derwentia (amphibian)|Derwentia]]'', ''[[Indobrachyops]]'', and ''[[Rewana]]''. Derwentiinae was named in a 2011 study that analyzed the [[phylogenetic]] relationships of rhytidosteids. It was a replacement name for the family Derwentiidae, which was named in 2000.

==Description== Like many other Permian and Triassic temnospondyls, derwentiines are known primarily from their skulls, which are triangular or rounded when viewed from above. Derwentiines are diagnosed as a [[clade]] (evolutionary grouping) by several shared characteristics or [[synapomorphies]]: a [[palate]] with a nearly straight back margin, a [[parasphenoid]] bone at the back of the palate that is covered in small bumps, an [[ectopterygoid]] bone on the palate that forms part of the border of a large hole called the [[subtemporal fossa]], and a [[postorbital bone]] behind the eye that is rounded or squarish. Although derwentiines are considered the most [[Synapomorphy|derived]] rhytidosteids, the last characteristic is shared with the most primitive rhytidosteids and non-rhytidosteid temnospondyls, suggesting an evolutionary reversal. The small bumps covering the parasphenoid are an unambiguous synapomorphy because the characteristic is only in derwentiines, while all other synapomorphies are ambiguous because they are also present in some other temnospondyls such as ''[[Chomatobatrachus]]'' and ''[[Lapillopsis]]''.<ref name=DSM11>{{cite journal |last=Dias-da-Silva |first=S. |author2=Marsicano, C. |year=2011 |title=Phylogenetic reappraisal of Rhytidosteidae (Stereospondyli: Trematosauria), temnospondyl amphibians from the Permian and Triassic |journal=Journal of Systematic Palaeontology |volume=9 |issue=2 |pages=305–325 |doi=10.1080/14772019.2010.492664|hdl=11336/68471 |hdl-access=free }}</ref>

==Classification== Derwentiidae was named in 2000 as a family of Australian temnospondyls in the suborder [[Stereospondyli]]. The subfamily Derwentiinae was named in 2011 as a replacement for Derwentiidae because all of these Australian temnospondyls were found to be members of the family Rhytidosteidae. The 2011 analysis also placed ''Indobrachyops'' from India in Derwentiinae as the first non-Australian member of the group. Below is a [[cladogram]] from the analysis, showing the phylogenetic relationships of derwentiines and other stereospondyls:<ref name=DSM11/>

{{clade| style=font-size:80%;line-height:100% |label1=[[Stereospondyli]] |1={{clade |1=''[[Benthosuchus]]'' |2=''[[Watsonisuchus]]'' |3={{clade |1={{clade |1=''[[Uruyiella]]'' |2={{clade |1=''[[Peltobatrachus]]'' |2={{clade |1=''[[Rhineceps]]'' |2={{clade |1=''[[Australerpeton]]'' |2=''[[Rhytidosteus]]''}} }} }} }} |2={{clade |1={{clade |1=''[[Lapillopsis]]'' |2=''[[Lydekkerina]]''}} |label2=[[Trematosauria]] |2={{clade |1=''[[Trematosaurus]]'' |2={{clade |1=''[[Luzocephalus]]'' |2={{clade |1=''[[Chomatobatrachus]]'' |2={{clade |label1=[[Brachyopoidea]] |1={{clade |1=''[[Bothriceps]]'' |2={{clade |1=''[[Xenobrachyops]]'' |2=''[[Keratobrachyops]]''}} }} |label2=[[Rhytidosteidae]] |2={{clade |1={{clade |1=''[[Nanolania]]'' |2=''[[Trucheosaurus]]''}} |2={{clade |1=''[[Boreopelta]]'' |2={{clade |1=''[[Peltostega]]'' |2={{clade |1={{clade |1=''[[Pneumatostega]]'' |2={{clade |1=''[[Sangaia]]'' |2=''[[Mahavisaurus]]''}} }} |label2='''Derwentiinae''' |2={{clade |1=''[[Deltasaurus]]'' |2={{clade |1=''[[Arcadia (genus)|Arcadia]]'' |2={{clade |1=''[[Rewana]]'' |2=''[[Acerastia]]'' |3={{clade |1=''[[Derwentia (amphibian)|Derwentia]]'' |2=''[[Indobrachyops]]'' }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }}

==References== {{Reflist}}

[[Category:Stereospondyli]] [[Category:Permian temnospondyls]] [[Category:Triassic temnospondyls]] [[Category:Prehistoric amphibians of Australia]]