Editing Reptile (section)

===Anapsids, synapsids, diapsids, and sauropsids===
[[File:Skull comparison.png|thumb|left|upright|A&nbsp;=&nbsp;Anapsid,<br /> B&nbsp;=&nbsp;Synapsid,<br /> C&nbsp;=&nbsp;Diapsid]]

It was traditionally assumed that the first reptiles retained an [[anapsid]] skull inherited from their ancestors.<ref name=Coven>{{cite book |author=Coven, R. |year=2000 |title=History of Life |publisher=[[Blackwell Science]] |place=Oxford, UK |page=[https://books.google.com/books?id=qvyBS4gwPF4C&dq=diapsids+ancestors+synapsids&pg=PA154 154] |via=Google Books}}</ref> This type of skull has a [[skull roof]] with only holes for the nostrils, eyes and a [[pineal eye]].<ref name="Romer, A 1977">{{cite book |author1-link=Alfred Romer |author1=Romer, A.S. |author2=Parsons, T.S. |orig-year=1977 |title=The Vertebrate Body |edition=5th |publisher=Saunders |place=Philadelphia, PA  |year=1985}}</ref> The discoveries of [[synapsid]]-like openings (see below) in the skull roof of the skulls of several members of [[Parareptilia]] (the clade containing most of the amniotes traditionally referred to as "anapsids"), including [[Lanthanosuchoidea|lanthanosuchoids]], [[Millerettidae|millerettids]], [[Bolosauridae|bolosaurids]], some [[Nycteroleteridae|nycteroleterids]], some [[Procolophonoidea|procolophonoids]] and at least some [[mesosaur]]s<ref>{{cite journal |author1=Cisneros, Juan C. |author2=Damiani, Ross |author3=Schultz, Cesar |author4=da&nbsp;Rosa, Átila |author5=Schwanke, Cibele |author6=Neto, Leopoldo W. |author7=Aurélio, Pedro L.P. |year=2004 |title=A procolophonoid reptile with temporal fenestration from the middle Triassic of Brazil |journal=Proceedings of the Royal Society B |volume=271 |issue=1547 |pages=1541–1546 |doi=10.1098/rspb.2004.2748 |pmid=15306328 |pmc=1691751}}</ref><ref name=TsujiMuller2009FR>{{cite journal |author1=Tsuji, Linda A. |author2=Müller, Johannes |name-list-style=amp |year=2009 |title=Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade |journal=Fossil Record |volume=12 |issue=1 |pages=71–81 |doi=10.1002/mmng.200800011 |bibcode=2009FossR..12...71T |doi-access=free}}</ref><ref name=PineiroetalCRP2012>{{cite journal |author1=Piñeiro, Graciela |author2=Ferigolo, Jorge |author3=Ramos, Alejandro |author4=Laurin, Michel |year=2012 |title=Cranial morphology of the Early Permian mesosaurid ''Mesosaurus tenuidens'' and the evolution of the lower temporal fenestration reassessed |journal=Comptes Rendus Palevol |volume=11 |issue=5 |pages=379–391 |doi=10.1016/j.crpv.2012.02.001 |bibcode=2012CRPal..11..379P }}</ref> made it more ambiguous and it is currently uncertain whether the ancestral amniote had an anapsid-like or synapsid-like skull.<ref name=PineiroetalCRP2012/> These animals are traditionally referred to as "anapsids", and form a [[paraphyly|paraphyletic]] basic stock from which other groups evolved.<ref name=modestoanderson2004/> Very shortly after the first amniotes appeared, a lineage called [[Synapsida]] split off; this group was characterized by a temporal opening in the skull behind each eye giving room for the jaw muscle to move. These are the "mammal-like amniotes", or stem-mammals, that later gave rise to the true [[mammals]].<ref>{{cite journal |last1=van&nbsp;Tuninen |first1=M. |last2=Hadly |first2=E.A. |year=2004 |title=Error in estimation of rate and time inferred from the early amniote fossil record and avian molecular clocks |journal=Journal of Molecular Biology |volume=59 |issue=2 |pages=267–276 |pmid=15486700 |doi=10.1007/s00239-004-2624-9 |bibcode=2004JMolE..59..267V |s2cid=25065918}}</ref> Soon after, another group evolved a similar trait, this time with a double opening behind each eye, earning them the name [[Diapsida]] ("two arches").<ref name=Coven/> The function of the holes in these groups was to lighten the skull and give room for the jaw muscles to move, allowing for a more powerful bite.<ref name="Romer, A 1977"/>

Turtles have been traditionally believed to be surviving parareptiles, on the basis of their anapsid skull structure, which was assumed to be primitive trait.<ref>{{cite book |last=Benton |first=M.J. |orig-year=2000 |title=Vertebrate Paleontology |publisher=Blackwell Science |location=London, UK |isbn=978-0-632-05637-8 |title-link=Vertebrate Paleontology (Benton) |edition=3rd |year=2004}} {{ISBN| 978-0-632-05614-9 }}</ref> The rationale for this classification has been disputed, with some arguing that turtles are diapsids that evolved anapsid skulls, improving their armor.<ref name="Laurin 95"/> Later morphological [[phylogenetics|phylogenetic]] studies with this in mind placed turtles firmly within Diapsida.<ref name=Rieppel>{{cite journal |vauthors=Rieppel O, de Braga M |year=1996 |title=Turtles as diapsid reptiles |journal=[[Nature (journal)|Nature]] |volume=384 |issue= 6608 |pages=453–455 |doi=10.1038/384453a0 |bibcode=1996Natur.384..453R |s2cid=4264378 |url=http://doc.rero.ch/record/16242/files/PAL_E3477.pdf }}</ref> All [[Molecular phylogenetics|molecular]] studies have strongly upheld the placement of turtles within diapsids, most commonly as a sister group to extant [[archosaur]]s.<ref name=Zardoya>{{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 USA]] |volume=95 |issue=24 |pages=14226–14231 |doi=10.1073/pnas.95.24.14226 |doi-access=free |pmid=9826682 |pmc=24355 |bibcode=1998PNAS...9514226Z}}</ref><ref name=Iwabe>{{cite journal |author1=Iwabe, 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 |doi-access=free |pmid = 15625185 }}</ref><ref name =Roos>{{cite journal |last1 = Roos |first1 = Jonas |last2= Aggarwal |first2=Ramesh K. |last3=Janke |first3=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 = "Katsu">{{Cite journal | last1 = Katsu | first1 = Y. | last2= Braun |first2=E.L. |last3=Guillette |first3=L.J. Jr. |last4=Iguchi |first4=T. | 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 | date = 2010-03-17 | doi = 10.1159/000297715 | pmid = 20234127| s2cid = 12116018 }}</ref>