Neodiapsida is a clade, 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 ...

s apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade

Sauria Sauria is the clade containing the most recent common ancestor of archosaurs (such as crocodilians, dinosaurs, etc.) and lepidosaurs (lizards and kin), and all its descendants. Since most molecular phylogenies recover turtles as more closely r ...

. The oldest known neodiapsid is generally considered to be ''

Orovenator ''Orovenator'' is an extinct genus of diapsid from Lower Permian (Artinskian stage) deposits of Oklahoma, United States. It is known from two partial skulls from the Richards Spur locality in Oklahoma. The holotype OMNH 74606 consists of ...

'' 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

drepanosaur Drepanosaurs (members of the clade Drepanosauromorpha) are a group of extinct reptiles that lived between the Carnian and Rhaetian stages of the late Triassic Period, approximately between 230 and 210 million years ago. The various species of d ...

s. The position of the highly derived Mesozoic marine reptile groups

Thalattosauria Thalattosauria ( Greek for "sea lizards") is an extinct order of prehistoric marine reptiles that lived in the middle to late Triassic period. Thalattosaurs were diverse in size and shape, and are divided into two superfamilies: Askeptosauroidea ...

Ichthyosauromorpha The Ichthyosauromorpha are an extinct clade of marine reptiles consisting of the Ichthyosauriformes and the Hupehsuchia, living during the Mesozoic. The node clade Ichthyosauromorpha was first defined by Ryosuke Motani ''et al.'' in 2014 as t ...

and

Sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria bec ...

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 o ...

definition by Laurin in 1991. He defined it as the branch-based clade containing all animals more closely related to "Younginiformes" (later, more specifically, emended to ''

Youngina capensis ''Youngina'' is an extinct genus of diapsid reptile from the Late Permian Beaufort Group ('' Tropidostoma''-''Dicynodon'' zones) of the Karoo Red Beds of South Africa. This, and a few related forms, make up the family Younginidae, within the Or ...

'') than to ''

Petrolacosaurus ''Petrolacosaurus'' ("rock lake lizard") is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, long reptile, and the earliest known reptile with two temporal fenestrae (holes at the rear part of the skull) ...

''. 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