Editing Diapsid (section)

==Classification==
Diapsids were originally classified as one of four subclasses of the class [[Reptilia]], all of which were based on the number and arrangement of openings in the skull. The other three subclasses were [[Synapsida]] (one opening low on the skull, for the "mammal-like reptiles"), [[Anapsid]]a (no skull opening, including turtles and their relatives), and [[Euryapsida]] (one opening high on the skull, including many prehistoric marine reptiles). With the advent of [[phylogenetic nomenclature]], this system of classification was heavily modified. Today, the synapsids are often not considered true reptiles, while Euryapsida were found to be an unnatural assemblage of diapsids that had lost one of their skull openings. Genetic studies and the discovery of the Triassic ''[[Pappochelys]]'' have shown that this is also the case in turtles, which are actually heavily modified diapsids. In phylogenetic systems, birds (descendants of traditional diapsid reptiles) are also considered to be members of this group.

Some modern studies of reptile relationships have preferred to use the name "diapsid" to refer to the crown group of all modern diapsid reptiles but not their extinct relatives. However, many researchers have also favored a more traditional definition that includes the prehistoric [[araeoscelidia]]ns. In 1991, Laurin defined Diapsida as a [[clade]], "the most recent common ancestor of araeoscelidians, [[lepidosaurs]], and [[archosaur]]s, and all its descendants".<ref name=bentonetal2015>Benton, M. J., Donoghue, P. C., Asher, R. J., Friedman, M., Near, T. J., & Vinther, J. (2015). "Constraints on the timescale of animal evolutionary history." ''Palaeontologia Electronica'', 18.1.1FC; 1-106; palaeo-electronica.org/content/fc-1</ref>

The clade Neodiapsida was given a [[phylogenetic]] 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]]'') than to ''[[Petrolacosaurus]]'' (representing [[Araeoscelidia]]).<ref>{{cite journal |last1=Reisz |first1=Robert R. |last2=Modesto |first2=Sean P. |last3=Scott |first3=Diane M. |date=22 December 2011 |title=A new Early Permian reptile and its significance in early diapsid evolution |journal=Proceedings of the Royal Society B: Biological Sciences |volume=278 |issue=1725 |pages=3731–3737 |doi=10.1098/rspb.2011.0439 |pmc=3203498 |pmid=21525061}}</ref> The earliest known neodiapsids like ''[[Orovenator]]'' are known from the Early [[Permian]], around 290 million years ago.<ref>{{Cite journal |last1=Reisz |first1=Robert R. |last2=Modesto |first2=Sean P. |last3=Scott |first3=Diane M. |date=2011-12-22 |title=A new Early Permian reptile and its significance in early diapsid evolution |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1725 |pages=3731–3737 |doi=10.1098/rspb.2011.0439 |issn=0962-8452 |pmc=3203498 |pmid=21525061}}</ref>

All [[Molecular phylogenetics|genetic]] studies have supported the hypothesis that turtles are diapsid reptiles; some have placed turtles within archosauromorpha,<ref name="scaffold201322">{{Cite journal |last1=Lee |first1=M. S. Y. |year=2013 |title=Turtle origins: Insights from phylogenetic retrofitting and molecular scaffolds |journal=Journal of Evolutionary Biology |volume=26 |issue=12 |pages=2729–2738 |doi=10.1111/jeb.12268 |pmid=24256520 |s2cid=2106400 |doi-access=free}}</ref><ref name="Mannen2">{{Cite journal |last=Mannen |first=Hideyuki |author2=Li, Steven S. -L. |date=Oct 1999 |title=Molecular evidence for a clade of turtles |journal=[[Molecular Phylogenetics and Evolution]] |volume=13 |issue=1 |pages=144–148 |doi=10.1006/mpev.1999.0640 |pmid=10508547|bibcode=1999MolPE..13..144M }}</ref> or, more commonly, as a sister group to extant archosaurs.<ref name="Zardoya2">{{cite journal |last1=Zardoya |first1=R. |last2=Meyer |first2=A. |year=1998 |title=Complete mitochondrial genome suggests diapsid affinities of turtles |journal=[[Proceedings of the National Academy of Sciences|Proc Natl Acad Sci U S A]] |volume=95 |issue=24 |pages=14226–14231 |bibcode=1998PNAS...9514226Z |doi=10.1073/pnas.95.24.14226 |issn=0027-8424 |pmc=24355 |pmid=9826682 |doi-access=free}}</ref><ref name="Iwabe2">{{Cite journal |last=Iwabe |first=N. |author2=Hara, Y. |author3=Kumazawa, Y. |author4=Shibamoto, K. |author5=Saito, Y. |author6=Miyata, T. |author7=Katoh, K. |date=2004-12-29 |title=Sister group relationship of turtles to the bird-crocodilian clade revealed by nuclear DNA-coded proteins |journal=[[Molecular Biology and Evolution]] |volume=22 |issue=4 |pages=810–813 |doi=10.1093/molbev/msi075 |pmid=15625185 |doi-access=free}}</ref><ref name="Roos2">{{Cite journal |last=Roos |first=Jonas |author2=Aggarwal, Ramesh K. |author3=Janke, Axel |date=Nov 2007 |title=Extended mitogenomic phylogenetic analyses yield new insight into crocodylian evolution and their survival of the Cretaceous–Tertiary boundary |journal=[[Molecular Phylogenetics and Evolution]] |volume=45 |issue=2 |pages=663–673 |doi=10.1016/j.ympev.2007.06.018 |pmid=17719245|bibcode=2007MolPE..45..663R }}</ref><ref name="Katsu2">{{Cite journal |last=Katsu |first=Y. |author2=Braun, E. L. |author3=Guillette, L. J. Jr. |author4=Iguchi, T. |date=2010-03-17 |title=From reptilian phylogenomics to reptilian genomes: analyses of c-Jun and DJ-1 proto-oncogenes |journal=Cytogenetic and Genome Research |volume=127 |issue=2–4 |pages=79–93 |doi=10.1159/000297715 |pmid=20234127 |s2cid=12116018}}</ref>

Modern reptiles and birds are placed within the neodiapsid subclade [[Sauria]], defined as the last common ancestor of Lepidosauria (which includes lizards, snakes and the tuatara), and Archosauria (which includes crocodilians and dinosaurs, including birds, among others).<ref name="Simões2022">{{Cite journal |last1=Simões |first1=Tiago R. |last2=Kammerer |first2=Christian F. |last3=Caldwell |first3=Michael W. |last4=Pierce |first4=Stephanie E. |name-list-style=and |year=2022 |title=Successive climate crises in the deep past drove the early evolution and radiation of reptiles |journal=Science Advances |volume=8 |issue=33 |pages=eabq1898 |bibcode=2022SciA....8.1898S |doi=10.1126/sciadv.abq1898 |pmc=9390993 |pmid=35984885 |doi-access=free}}</ref>

A cladistic analysis by Laurin and Piñeiro (2017) recovers [[Parareptilia]] as part of Diapsida, with pareiasaurs, turtles, millerettids, and procolophonoids recovered as more derived than the basal diapsid ''[[Younginia]]''.<ref>{{Cite journal |last1=Laurin |first1=Michel |last2=Piñeiro |first2=Graciela H. |year=2017 |title=A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes |url=https://hal.archives-ouvertes.fr/hal-01618314/file/Laurin%20%26%20Pin%CC%83eiro%20ms%20R1%20cl.pdf |journal=Frontiers in Earth Science |volume=5 |page=88 |bibcode=2017FrEaS...5...88L |doi=10.3389/feart.2017.00088 |s2cid=32426159 |doi-access=free}}</ref> A 2020 study by David P. Ford and Roger B. J. Benson also recovered Parareptilia as deeply nested within Diapsida as the sister group to [[Neodiapsida]]. They united this relationship between Parareptilia and Neodiapsida in the new clade [[Neoreptilia]], defining it as the last common ancestor and all descendants of ''[[Procolophon trigoniceps]]'' and ''[[Youngina capensis]]''.<ref name=":5">{{cite journal |vauthors=Ford DP, Benson RB |date=January 2020 |title=The phylogeny of early amniotes and the affinities of Parareptilia and Varanopidae |url=https://ora.ox.ac.uk/objects/uuid:cb6f5486-7889-47fe-beff-515795468442 |journal=Nature Ecology & Evolution |volume=4 |issue=1 |pages=57–65 |doi=10.1038/s41559-019-1047-3 |pmid=31900445 |s2cid=209673326}}</ref> However, this excludes [[mesosaur]]s, who were found to be basal among the sauropsids.<ref name=":5">{{cite journal |vauthors=Ford DP, Benson RB |date=January 2020 |title=The phylogeny of early amniotes and the affinities of Parareptilia and Varanopidae |url=https://ora.ox.ac.uk/objects/uuid:cb6f5486-7889-47fe-beff-515795468442 |journal=Nature Ecology & Evolution |volume=4 |issue=1 |pages=57–65 |doi=10.1038/s41559-019-1047-3 |pmid=31900445 |s2cid=209673326}}</ref> Other recent studies have found the more traditional arrangement of parareptiles being outside of Diapsida.<ref name="Simões2022" />

The position of the highly derived Mesozoic marine reptile groups [[Thalattosauria]], [[Ichthyosauromorpha]] and [[Sauropterygia]] within Neodiapsida is uncertain, and they may lie within Sauria.<ref name="Simões2022" />
===Relationships===
Below are [[cladogram|cladograms]] showing the relations of the major groups of diapsids.

Cladogram after Bickelmann ''et al.'', 2009<ref name="Bickelmann09">{{cite journal |last1=Bickelmann |first1=Constanze |last2=Müller |first2=Johannes |last3=Reisz |first3=Robert R. |name-list-style=and |year=2009 |title=The enigmatic diapsid ''Acerosodontosaurus piveteaui'' (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of ''younginiform'' reptiles |journal=Canadian Journal of Earth Sciences |volume=49 |issue=9 |pages=651–661 |bibcode=2009CaJES..46..651S |doi=10.1139/E09-038}}</ref> and Reisz ''et al.'', 2011:<ref name="Orovenator">{{cite journal |last1=Reisz |first1=Robert R. |last2=Modesto |first2=Sean P. |last3=Scott |first3=Diane M. |name-list-style=and |year=2011 |title=A new Early Permian reptile and its significance in early diapsid evolution |journal=Proceedings of the Royal Society B |volume=278 |issue=1725 |pages=3731–7 |doi=10.1098/rspb.2011.0439 |pmc=3203498 |pmid=21525061}}</ref>

{{clade
|1={{clade
      |label1=[[Sauropsida]] 
      |1={{clade
         |label1={{extinct}}[[Parareptilia]] 
         |1={{clade
               |1={{clade
                  |label1=      
                  |1={{extinct}}[[Millerettid]]ae [[Image:Milleretta BW.jpg|50px]]
                  }}
               |label2=  
               |2={{clade
                  |1={{clade
                     |label1=    
                     |1= {{extinct}}''[[Eunotosaurus]]''
                     }}
                  |label2={{extinct}}[[Hallucicrania]] 
                  |2={{clade
                    |1={{extinct}}[[Lanthanosuchidae]] [[Image:Lanthanosuchus watsoni.jpg|50px]]
                    |label2={{extinct}}[[Procolophonia]] 
                    |2={{clade
                        |label1=  
                        |1={{extinct}}[[Procolophonoidea]] [[Image:Sclerosaurus1DB.jpg|50px]]
                        |2={{extinct}}[[Pareiasauromorpha]] [[Image:Scutosaurus BW.jpg|60px]]
                        }}
                     }}
                 }}
             }}
      |label2=[[Eureptilia]]
      |2={{clade
         |1={{clade
            |label1=    
            |1= {{extinct}}[[Captorhinidae]] [[Image:Labidosaurus.jpg|50px]]
            }}
         |label2=[[Romeriida]] 
         |2={{clade
            |1={{clade
               |label1=   
               |1={{extinct}}''[[Paleothyris]]''
               }}
            |label2='''Diapsida''' 
            |2={{clade
               |1={{extinct}}[[Araeoscelidia]]
               |label2=[[Neodiapsida]] 
               |2={{clade
                  |label1=  
                  |1={{extinct}}''[[Orovenator]]''
                  |2={{clade
                     |label1= 
                     |1={{extinct}}''[[Lanthanolania]]''
                     |2={{clade
                        |label1= 
                        |1={{extinct}}[[Tangasauridae]]
                        |2={{clade
                           |label1= 
                           |1={{extinct}}[[Younginidae]]
                           |2={{clade
                              |label1= 
                              |1={{clade
                                 |label1=  
                                 |1={{extinct}}''[[Claudiosaurus]]''
                                 }}
                              |2={{clade
                                 |label1= 
                                 |1={{clade
                                    |label1= 
                                    |1={{clade
                                       |label1= 
                                       |1={{extinct}}''[[Palaeagama]]''
                                       |2={{extinct}}''[[Saurosternon]]''
                                       }}
                                    }}
                                 |2={{clade
                                    |label1= 
                                    |1={{clade
                                       |label1=  
                                       |1={{extinct}}''[[Coelurosauravus]]''
                                       }}
                                    |2={{clade
                                       |1={{clade
                                          |label1= 
                                          |1={{extinct}}[[Thalattosauria]]
                                          |2={{clade
                                             |label1= 
                                             |1={{extinct}}[[Hupehsuchia]]
                                             |2={{extinct}}[[Ichthyopterygia]]
                                             }}
                                          }}
                                       |label2=[[Sauria]] 
                                       |2={{clade
                                          |label1= 
                                          |1=[[Lepidosauromorpha]]
                                          |2=[[Archosauromorpha]]
                                          }}
                                       }}
                                   }}
                              }}
                          }}
                      }}
  }} }} }} }} }} }} }}
}}
}}

The cladogram of Lee (2013) below used a combination of genetic (molecular) and fossil (morphological) data.<ref name="scaffold2013">{{Cite journal |last1=Lee |first1=M. S. Y. |year=2013 |title=Turtle origins: Insights from phylogenetic retrofitting and molecular scaffolds |journal=Journal of Evolutionary Biology |volume=26 |issue=12 |pages=2729–2738 |doi=10.1111/jeb.12268 |pmid=24256520 |s2cid=2106400 |doi-access=free}}</ref>

{{clade|{{clade
               |1={{extinct}}[[Araeoscelidia]] [[Image:Spinoaequalis schultzei reconstruction.jpg|50px]]
               |label2=Neodiapsida
               |2={{clade
               |1={{extinct}}''[[Claudiosaurus]]''[[File:Claudiosaurus white background.jpg|80px]]
               |2={{clade
                  |1={{extinct}}[[Younginiformes]][[File:Hovasaurus BW flipped.jpg|80px]]
                  |label2=[[Sauria]]
                  |2={{clade
                     |label1=[[Lepidosauromorpha]]
                     |1={{clade
                         |1={{extinct}}[[Kuehneosauridae]][[File:Icarosaurus white background.jpg|80px]]
                         |label2=[[Lepidosauria]]
                         |2={{clade
                            |1=[[Rhynchocephalia]] ([[tuatara]] and their extinct relatives)[[File:Hatteria white background.jpg|80px]]
                            |2=[[Squamata]] ([[lizard]]s and [[snake]]s)[[File:British reptiles, amphibians, and fresh-water fishes (1920) (Lacerta agilis).jpg|80px]]}} }}
                     |label2=[[Archosauromorpha]]
                     |2={{clade
                        |1={{clade
                           |1={{extinct}}[[Choristodera]][[File:Hyphalosaurus_mmartyniuk_wiki.png|80px]]
                           |2={{clade
                              |1={{extinct}}[[Prolacertiformes]][[File:Prolacerta broomi.jpg|80px]]
                              |2={{clade
                                   |1={{clade
                                      |1={{extinct}}[[Rhynchosaur]]ia[[File:Hyperodapedon BW2 white background.jpg|80px]]
                                      |2={{extinct}}''[[Trilophosaurus]]''[[File:Trilophosaurus buettneri (flipped).jpg|80px]]
                                      }}
                                   |2=[[Archosauriformes]]  ([[Crocodilia|crocodiles]], [[bird]]s, and their extinct relatives) <span style="{{MirrorH}}">[[File:Deinosuchus riograndensis.png|80px]]</span>

}} }} }}

                        }}
                     }}
                  }}
               }}
            }}|label1=Diapsida}}

This second cladogram is based on the 2017 study by Pritchard and Nesbitt.<ref>{{Cite journal |last1=Pritchard |first1=Adam C. |last2=Nesbitt |first2=Sterling J. |date=2017-10-11 |title=A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida |journal=Royal Society Open Science |volume=4 |issue=10 |page=170499 |bibcode=2017RSOS....470499P |doi=10.1098/rsos.170499 |issn=2054-5703 |pmc=5666248 |pmid=29134065}}</ref>

{{clade|{{clade
      |1={{extinct}}''[[Orovenator]]''[[File:Orovenator.jpg|80px]]
      |2={{clade
         |1={{extinct}}[[Drepanosauromorpha]][[File:Megalancosaurus BW.jpg|80px]]
         |2={{clade
            |1={{extinct}}[[Weigeltisauridae]][[File:Weigeltisaurus_reconstruction.png|80px]]
            |2={{clade
               |1={{extinct}}''[[Claudiosaurus]]''[[File:Claudiosaurus white background.jpg|80px]]
               |2={{clade
                  |1={{extinct}}[[Tangasauridae]][[File:Hovasaurus BW flipped.jpg|80px]] (''[[Hovasaurus]]'', ''[[Thadeosaurus]]'', ''[[Acerosodontosaurus]]'')
                  |2={{extinct}}[[Younginidae]] (''[[Youngina]]''+unnamed species)
                  |label3=[[Sauria]]
                  |3={{clade
                     |1=[[Lepidosauria]][[File:Zoology of Egypt (1898) (Varanus griseus).png|80px]]
                     |label2=[[Archosauromorpha]]
                     |2={{clade
                        |1={{extinct}}''[[Protorosaurus]]''[[File:Protorosaurus BW.jpg|80px]]
                        |2={{clade
                           |1={{extinct}}[[Tanystropheidae]][[File:Macrocnemus BW.jpg|80px]]
                           |2={{clade
                              |1={{extinct}}[[Rhynchosauria]][[File:Hyperodapedon BW2 white background.jpg|80px]]
                              |2={{clade
                                 |1={{extinct}}[[Allokotosauria]][[File:Trilophosaurus buettneri (flipped).jpg|80px]]
                                 |2={{clade
                                    |1={{extinct}}''[[Prolacerta]]''[[File:Prolacerta broomi.jpg|80px]]
                                    |2=[[Archosauriformes]]<span style="{{MirrorH}}">[[File:Deinosuchus riograndensis.png|80px]]</span>
}} }} }} }} }} }} }} }} }} }} }}|label1=Neodiapsida}}

The following cladogram was found by Simões ''et al''. (2022): <ref name="Simões2022" />

{{clade
|label1={{vert-label|Neoreptilia}}
|{{clade
  |1={{extinct}}[[Procolophonomorpha]][[File:Scutosaurus BW.jpg|80px]]
  |label2={{vert-label|'''Neodiapsida'''}}
  |2={{clade
    |1={{extinct}}[[Younginiformes]][[File:Hovasaurus BW flipped.jpg|80px]]
    |2={{clade
      |1={{extinct}}''[[Eunotosaurus]]''
      |2={{clade
        |1={{extinct}}[[Weigeltisauridae]][[File:Weigeltisaurus_reconstruction.png|80px]]
        |label2={{vert-label|[[Sauria]]}}
        |2={{clade
          |label1=[[Lepidosauromorpha]]
          |1={{clade
            |1=[[Rhynchocephalia]] ([[tuatara]] and their extinct relatives)[[File:Hatteria white background.jpg|80px]]
            |2=[[Squamata]] ([[lizard]]s and [[snake]]s)[[File:British reptiles, amphibians, and fresh-water fishes (1920) (Lacerta agilis).jpg|80px]]}} 
            |label2=[[Archelosauria]]
              |2={{clade
              |1=[[Pantestudines]] ([[turtle]]s and extinct relatives)[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Centrochelys sulcata).jpg|50px]]
              |label2={{vert-label|[[Archosauromorpha]]}}
              |2={{clade
                |1={{clade
                  |1={{extinct}}[[Ichthyosauromorpha]][[File:Ichthyosaurus BW.jpg|80px]]
                  |2={{clade
                    |1={{extinct}}[[Sauropterygia]] [[File:Dolichorhynchops BW flipped.jpg|80px]]
                    |2={{extinct}}[[Thalattosauria]] [[File:Miodentosaurus BW.jpg|80px]]
                     }}
                   }}
                |2={{clade
                  |label1={{extinct}}[[Protorosauria]]
                  |1={{clade
                    |1={{extinct}}[[Protorosauridae]][[File:Protorosaurus BW.jpg|80px]]
                    |2={{clade
                      |1={{extinct}}[[Tanystropheidae]][[File:Macrocnemus BW.jpg|80px]]
                      |2={{clade
                        |1={{extinct}}[[Drepanosauromorpha]][[File:Megalancosaurus BW.jpg|80px]]
                        |2={{extinct}}[[Kuehneosauridae]][[File:Icarosaurus white background.jpg|80px]]
                         }}
                       }}
                     }}
                  |2={{clade
                    |1={{clade
                      |1={{extinct}}[[Allokotosauria]][[File:Trilophosaurus buettneri (flipped).jpg|80px]]
                      |2={{extinct}}[[Rhynchosaur]]ia[[File:Hyperodapedon BW2 white background.jpg|80px]]
                       }}
                    |2=[[Archosauriformes]]  ([[Crocodilia|crocodiles]], [[bird]]s, and their extinct relatives) <span style="{{MirrorH}}">[[File:Deinosuchus riograndensis.png|80px]]</span>
                     }}
                   }}
                 }}
               }}
             }}
           }}
         }}
      }}
   }}
}}