Neodiapsida is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

, or major branch, of the reptilian family tree, typically defined as including all

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years a ...

s apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade Sauria. The oldest known neodiapsid is generally considered to be '' Orovenator'' from the Early Permian (

Cisuralian The Cisuralian is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan and ...

) of North America. Basal-non saurian neodiaspids were ancestrally lizard-like, but basal Permian neodiapsids also include specialised swimming forms ('' Hovasaurus'') the gliding lizard-like Weigeltisauridae, as well as the Triassic chameleon-like drepanosaurs. The position of the highly derived Mesozoic marine reptile groups Thalattosauria, Ichthyosauromorpha and Sauropterygia within Neodiapsida is uncertain, and they may lie within Sauria.

Classification

The clade Neodiapsida was given a

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 ...

definition by Laurin in 1991. He defined it as the branch-based

containing all animals more closely related to "Younginiformes" (later, more specifically, emended to '' Youngina capensis'') than to '' Petrolacosaurus''. The

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 ...

presented here illustrates the "family tree" of reptiles, and follows a simplified version of the relationships found by M.S. Lee, in 2013. All genetic studies have supported the hypothesis that turtles are diapsid reptiles; some have placed turtles within archosauromorpha, or, more commonly, as a sister group to extant archosaurs. though a few have recovered turtles as lepidosauromorphs instead. The cladogram below used a combination of genetic (molecular) and fossil (morphological) data to obtain its results. This second cladogram is based on the 2017 study by Pritchard and Nesbiit.

References

* Callaway, J.M. (1997), Ichthyosauria: Introduction, in JM Callaway & EL Nicholls (eds.), Ancient Marine Reptiles. Academic Press, pp. 3–16. * Laurin, Michel and Gauthier, Jacques A. (2000
Autapomorphies of Diapsid Clades

External links

cladogram {{Taxonbar, from=Q3497035 Reptile taxonomy Guadalupian first appearances Extant Permian first appearances Taxa named by Michael Benton