A new taxon of cistecephalid dicynodont from the upper Permian Kundaram Formation of India

A new cistecephalid dicynodont, Sauroscaptor tharavati gen. et sp. nov., is described from the upper Permian Kundaram Formation of India. This taxon is represented by specimens formerly referred to the African dicynodont genera Cistecephalus and Emydops. Sauroscaptor can be distinguished from other cistecephalids by the extremely posterior position of the pineal foramen (overhanging the edge of the occiput), bipartite nuchal crest, and relatively narrow skull roof. The recognition of Sauroscaptor as a distinct cistecephalid taxon adds to the increasing evidence for high levels of basinal endemism in this family. However, dicynodont biogeographical patterns are complex, and there is no simple relationship between inferred dispersal ability based on body size and levels of endemicity within clades.本文记述了产自印度上二叠统昆达拉姆组（Kundaram Formation）的石头龙科二齿兽类（cistecephalid dicynodont）新属新种——蜥头龙（Sauroscaptor tharavati gen. et sp. nov.）。该类群的化石标本此前曾被归入非洲的石头龙属（Cistecephalus）与泽鳄头龙属（Emydops）。相较于其他石头龙科类群，蜥头龙可通过以下特征加以区分：松果孔（pineal foramen）位置极度靠后，延伸至枕骨边缘上方；颈脊（nuchal crest）分为两部分；颅顶（skull roof）相对狭窄。将蜥头龙认定为独立的石头龙科类群，进一步补充了该类群存在高度盆地特有性（basinal endemism）的相关证据。不过二齿兽类的生物地理分布模式（biogeographical patterns）较为复杂，基于体型推断的扩散能力与演化支（clade）内的特有性（endemicity）水平之间并无简单的对应关系。