Editing Reptile (section)

==Evolutionary history==
{{Main|Evolution of reptiles}}

===Origin of the reptiles===
[[File:Hylonomus BW.jpg|thumb|An early reptile ''[[Hylonomus]]'']]
[[File:Europasaurus holgeri Scene 2.jpg|thumb|Mesozoic scene showing typical reptilian megafauna: [[dinosaur]]s including ''[[Europasaurus holgeri]]'', [[iguanodont]]s, and ''[[Archaeopteryx lithographica]]'' perched on the foreground tree stump]]

The origin of the reptiles lies about 310–320 million years ago, in the steaming swamps of the late [[Carboniferous]] period, when the first reptiles evolved from advanced [[Reptiliomorpha|reptiliomorphs]].<ref name="Laurin 95">
{{Cite journal |author1=Laurin, M. |author2=Reisz, R.R. |year=1995 |title=A reevaluation of early amniote phylogeny |journal=[[Zoological Journal of the Linnean Society]] |volume=113 |issue=2 |pages=165–223 |doi=10.1111/j.1096-3642.1995.tb00932.x |doi-access=free |url=http://www.iucn-tftsg.org/wp-content/uploads/file/Articles/Laurin_and_Reisz_1995.pdf}}</ref>{{Failed verification|date=May 2023|reason=Couldn't validate "310 million years ago"}}

The oldest known animal that may have been an [[amniote]] is ''[[Casineria]]'' (though it may have been a [[Temnospondyli|temnospondyl]]).<ref>{{cite journal | last1 = Paton | first1 = R.L. | last2 = Smithson | first2 = T.R. | last3 = Clack | first3 = J.A. | year = 1999 | title = An amniote-like skeleton from the Early Carboniferous of Scotland | journal = [[Nature (journal)|Nature]] | volume = 398 | issue = 6727| pages = 508–513 | doi=10.1038/19071| bibcode = 1999Natur.398..508P | s2cid = 204992355 }}</ref><ref>{{cite journal|last1=Monastersky |first1=R |year=1999 |title=Out of the Swamps, How early vertebrates established a foothold – with all 10 toes – on land |url=http://www.sciencenews.org/sn_arc99/5_22_99/bob1.htm |journal=Science News |volume=155 |issue=21 |pages=328–330 |doi=10.2307/4011517 |url-status=dead |archive-url=https://web.archive.org/web/20110604220710/http://www.sciencenews.org/sn_arc99/5_22_99/bob1.htm |archive-date=June 4, 2011 |jstor=4011517 |url-access=subscription }}</ref><ref>{{cite thesis |section=Chapter&nbsp;6: Walking with early tetrapods: evolution of the postcranial skeleton and the phylogenetic affinities of the Temnospondyli (Vertebrata: Tetrapoda) |first=Kat |last=Pawley |year=2006 |url=http://hdl.handle.net/1959.9/57256 |title=The postcranial skeleton of temnospondyls (Tetrapoda: temnospondyli) |degree=PhD |publisher=La Trobe University |place=Melbourne, AU |hdl=1959.9/57256}}</ref> A series of footprints from the fossil strata of [[Nova Scotia]] dated to {{val|315|ul=Ma}} show typical reptilian toes and imprints of scales.<ref>{{cite journal | last1 = Falcon-Lang | first1 = H.J. | last2 = Benton | first2 = M.J. | last3 = Stimson | first3 = M. | year = 2007 | title = Ecology of early reptiles inferred from Lower Pennsylvanian trackways | journal = [[Journal of the Geological Society]] | volume = 164 | issue = 6| pages = 1113–1118 | doi=10.1144/0016-76492007-015| citeseerx = 10.1.1.1002.5009 | s2cid = 140568921 }}</ref> These tracks are attributed to ''[[Hylonomus]]'', the oldest unquestionable reptile known.<ref>{{cite web|url=http://www.sflorg.com/sciencenews/scn101707_01.html |title=Earliest Evidence For Reptiles |publisher=Sflorg.com |date=2007-10-17 |access-date=March 16, 2010|url-status=dead |archive-url=https://web.archive.org/web/20110716044246/http://www.sflorg.com/sciencenews/scn101707_01.html |archive-date=July 16, 2011 }}</ref>
It was a small, lizard-like animal, about {{convert|20|to|30|cm}} long, with numerous sharp teeth indicating an insectivorous diet.<ref name=EoDP>{{cite book |editor=Palmer, D.|year=1999 |title= The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|publisher= Marshall Editions|location=London|page= 62|isbn= 978-1-84028-152-1}}</ref> Other examples include ''[[Westlothiana]]'' (for the moment considered a [[Reptiliomorpha|reptiliomorph]] rather than a true [[amniote]])<ref>{{cite journal | last1 = Ruta | first1 = M. | last2 = Coates | first2 = M.I. | last3 = Quicke | first3 = D.L.J. | year = 2003 | title = Early tetrapod relationships revisited | url = http://pondside.uchicago.edu/oba/faculty/coates/5.RutCoaQuick2003.pdf | journal = Biological Reviews | volume = 78 | issue = 2 | pages = 251–345 | doi = 10.1017/S1464793102006103 | pmid = 12803423 | s2cid = 31298396 | access-date = 2010-08-19 | archive-date = 2008-05-22 | archive-url = https://web.archive.org/web/20080522124644/http://pondside.uchicago.edu/oba/faculty/coates/5.RutCoaQuick2003.pdf | url-status = dead }}</ref> and ''[[Paleothyris]]'', both of similar build and presumably similar habit.

However, [[microsaur]]s have been at times considered true reptiles, so an earlier origin is possible.<ref name="auto">{{Cite journal|title=The First Age of Reptiles? Comparing Reptile and Synapsid Diversity, and the Influence of Lagerstätten, During the Carboniferous and Early Permian|first=Neil|last=Brocklehurst|date=July 31, 2021|journal=Frontiers in Ecology and Evolution|volume=9|doi=10.3389/fevo.2021.669765|doi-access=free}}</ref>

===Rise of the reptiles===
The earliest amniotes, including stem-reptiles (those amniotes closer to modern reptiles than to mammals), were largely overshadowed by larger stem-tetrapods, such as ''[[Cochleosaurus]]'', and remained a small, inconspicuous part of the fauna until the [[Carboniferous Rainforest Collapse]].<ref name="SahneyBentonFalconLang 2010RainforestCollapse">{{cite journal |author=Sahney |first1=S. |last2=Benton |first2=M.J. |last3=Falcon-Lang |first3=H.J. |year=2010 |title=Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica |journal=Geology |volume=38 |issue=12 |pages=1079–1082 |bibcode=2010Geo....38.1079S |doi=10.1130/G31182.1}}</ref> This sudden collapse affected several large groups. Primitive tetrapods were particularly devastated, while stem-reptiles fared better, being ecologically adapted to the drier conditions that followed. Primitive tetrapods, like modern amphibians, need to return to water to lay eggs; in contrast, amniotes, like modern reptiles&nbsp;– whose eggs possess a shell that allows them to be laid on land&nbsp;– were better adapted to the new conditions. Amniotes acquired new niches at a faster rate than before the collapse and at a much faster rate than primitive tetrapods. They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores.<ref name="SahneyBentonFalconLang 2010RainforestCollapse"/> From this point forward, reptiles dominated communities and had a greater diversity than primitive tetrapods, setting the stage for the Mesozoic (known as the Age of Reptiles).<ref name=Sahney-Benton-Ferry-2010>{{cite journal |author1=Sahney, S. |author2=Benton, M.J. |author3=Ferry, P.A. |year=2010 |title=Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land |journal=Biology Letters |doi=10.1098/rsbl.2009.1024 |doi-access=free |volume=6 |pages=544–547 |issue=4 |pmid=20106856 |pmc=2936204}}</ref> One of the best known early stem-reptiles is ''[[Mesosaurus]]'', a genus from the [[Cisuralian|Early Permian]] that had returned to water, feeding on fish.

A 2021 examination of reptile diversity in the Carboniferous and the Permian suggests a much higher degree of diversity than previously thought, comparable or even exceeding that of synapsids. Thus, the "First Age of Reptiles" was proposed.<ref name="auto"/>

===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>

===Permian reptiles===
With the close of the [[Carboniferous]], the amniotes became the dominant tetrapod fauna. While primitive, terrestrial [[reptiliomorpha|reptiliomorphs]] still existed, the synapsid amniotes evolved the first truly terrestrial [[megafauna]] (giant animals) in the form of [[pelycosaurs]], such as ''[[Edaphosaurus]]'' and the carnivorous ''[[Dimetrodon]]''. In the mid-Permian period, the climate became drier, resulting in a change of fauna: The pelycosaurs were replaced by the [[therapsids]].<ref name="autogenerated2001">[[Edwin Harris Colbert|Colbert, E.H.]] & Morales, M. (2001): ''[[Evolution of the Vertebrates|Colbert's Evolution of the Vertebrates: A History of the Backboned Animals Through Time]]''. 4th edition. John Wiley & Sons, Inc, New York. {{ISBN|978-0-471-38461-8}}.</ref>

The parareptiles, whose massive [[skull roof]]s had no postorbital holes, continued and flourished throughout the Permian. The [[pareiasaur]]ian parareptiles reached giant proportions in the late Permian, eventually disappearing at the close of the period (the turtles being possible survivors).<ref name="autogenerated2001"/>

Early in the period, the modern reptiles, or [[Sauria|crown-group reptiles]], evolved and split into two main lineages: the [[Archosauromorpha]] (forebears of [[turtle]]s, [[crocodile]]s, and [[dinosaur]]s) and the [[Lepidosauromorpha]] (predecessors of modern [[lizard]]s and [[tuatara]]s). Both groups remained lizard-like and relatively small and inconspicuous during the Permian.

===Mesozoic reptiles===
The close of the Permian saw the greatest mass extinction known (see the [[Permian–Triassic extinction event]]), an event prolonged by the combination of two or more distinct extinction pulses.<ref name="SahneyBenton2008RecoveryFromProfoundExtinction">{{cite journal |author1=Sahney, S. |author2=Benton, M.J.  |name-list-style=amp | year=2008 | title=Recovery from the most profound mass extinction of all time | journal=Proceedings of the Royal Society B | doi=10.1098/rspb.2007.1370 |doi-access=free | volume = 275 | pages = 759–765| pmid=18198148 | issue=1636 | pmc=2596898}}</ref> Most of the earlier parareptile and synapsid megafauna disappeared, being replaced by the true reptiles, particularly [[archosauromorpha|archosauromorphs]]. These were characterized by elongated hind legs and an erect pose, the early forms looking somewhat like long-legged crocodiles. The [[archosaur]]s became the dominant group during the [[Triassic]] period, though it took 30 million years before their diversity was as great as the animals that lived in the Permian.<ref name="SahneyBenton2008RecoveryFromProfoundExtinction"/> Archosaurs developed into the well-known [[dinosaur]]s and [[pterosaur]]s, as well as the ancestors of [[crocodile]]s. Since reptiles, first [[rauisuchia]]ns and then dinosaurs, dominated the Mesozoic era, the interval is popularly known as the "Age of Reptiles". The dinosaurs also developed smaller forms, including the feather-bearing smaller [[theropoda|theropods]]. In the [[Cretaceous]] period, these gave rise to the first true [[birds]].<ref name=divergence>{{Cite journal | last1 = Lee | first1 = Michael SY | last2 = Cau | first2 = Andrea | last3 = Darren | first3 = Naish | last4 = Gareth J. | first4 = Dyke | year = 2013 | title = Morphological Clocks in Paleontology, and a Mid-Cretaceous Origin of Crown Aves | journal = Systematic Biology | doi = 10.1093/sysbio/syt110 |doi-access=free | pmid=24449041 | volume=63 | issue = 3 | pages=442–449}}</ref>

The [[sister group]] to Archosauromorpha is [[Lepidosauromorpha]], containing [[lizard]]s and [[tuatara]]s, as well as their fossil relatives. Lepidosauromorpha contained at least one major group of the Mesozoic sea reptiles: the [[mosasaurs]], which lived during the [[Cretaceous]] period. The phylogenetic placement of other main groups of fossil sea reptiles – the [[ichthyopterygia]]ns (including [[ichthyosaur]]s) and the [[sauropterygia]]ns, which evolved in the early Triassic – is more controversial. Different authors linked these groups either to lepidosauromorphs<ref name=Gauthier-1994-Prothero-Schoch>{{cite book |author=Gauthier, J.A. |year=1994 |section=The diversification of the amniotes |editor1=Prothero, D.R. |editor2=Schoch, R.M. |title=Major Features of Vertebrate Evolution |journal=Short Courses in Paleontology |volume=7 |pages=129–159 |place=Knoxville, TN |publisher=The Paleontological Society |doi=10.1017/S247526300000129X |chapter-url=https://www.cambridge.org/core/journals/short-courses-in-paleontology/article/abs/diversification-of-the-amniotes/EDBFD2920CC4B45A0BB6299C8B787F90 }}</ref> or to archosauromorphs,<ref>{{Cite journal |author=Merck, John W. |year=1997 |title=A phylogenetic analysis of the euryapsid reptiles |journal=Journal of Vertebrate Paleontology |volume=17 |issue=Supplement to 3 |pages=1–93|doi=10.1080/02724634.1997.10011028}}</ref><ref>{{cite conference |author1=Modesto, Sean |author2=Reisz, Robert |author3=Scott, Diane |year=2011 |title=A neodiapsid reptile from the Lower Permian of Oklahoma |conference=71st Annual Meeting |publisher=Society of Vertebrate Paleontology |series=Program and Abstracts |page=160}}</ref><ref>{{cite web |author=Holtz, T. |title=Fossil tetrapods |series=GEOL&nbsp;331 Vertebrate Paleontology&nbsp;II |type=class handouts |website=geol.umd.edu |publisher=[[University of Maryland]], Department of Geology |url=http://www.geol.umd.edu/~tholtz/G331/lectures/331vertsII.html}}</ref> and ichthyopterygians were also argued to be diapsids that did not belong to the least inclusive clade containing lepidosauromorphs and archosauromorphs.<ref>{{cite journal |author1=Motani, Ryosuke |author2=Minoura, Nachio |author3=Ando, Tatsuro |year=1998 |title=Ichthyosaurian relationships illuminated by new primitive skeletons from Japan |journal=[[Nature (journal)|Nature]] |volume=393 |issue=6682 |pages=255–257 |doi=10.1038/30473 |bibcode=1998Natur.393..255M |s2cid=4416186 }}</ref>

===Cenozoic reptiles===
[[File:Varanus priscus Melbourne Museum.jpg|thumb|''[[Megalania|Varanus priscus]]'' was a giant carnivorous [[goanna]] lizard, perhaps as long as 7&nbsp;metres and weighing up to 1,940&nbsp;kilograms<ref>{{cite book |author=Molnar, Ralph E. |year=2004 |title=Dragons in the Dust: The paleobiology of the giant monitor lizard Megalania |publisher=Indiana University Press |location=Bloomington |isbn=978-0-253-34374-1 }}</ref>]]
[[File:Champsosaurus natator.jpg|thumb|Skeleton of ''[[Champsosaurus]]'', a [[choristodere]], the latest surviving order of extinct reptiles. The last known choristoderes are known from the [[Miocene]], around 11.3 million years ago ]]
The close of the [[Cretaceous]] period saw the demise of the Mesozoic era reptilian megafauna (see the [[Cretaceous–Paleogene extinction event]], also known as K-T&nbsp;extinction event). Of the large [[marine reptile]]s, only [[sea turtle]]s were left; and of the non-marine large reptiles, only the semi-aquatic [[crocodilia|crocodiles]] and broadly similar [[Choristodera|choristoderes]] survived the extinction, with last members of the latter, the lizard-like ''[[Lazarussuchus]]'', becoming extinct in the [[Miocene]].<ref>{{cite journal |last=Evans |first=Susan E. |author2=Klembara, Jozef |year=2005 |title=A choristoderan reptile (Reptilia: Diapsida) from the Lower Miocene of northwest Bohemia (Czech Republic) |journal=Journal of Vertebrate Paleontology |volume=25 |issue=1 |pages=171–184 |doi=10.1671/0272-4634(2005)025[0171:ACRRDF]2.0.CO;2 |s2cid=84097919 }}</ref> Of the great host of dinosaurs dominating the Mesozoic, only the small beaked [[birds]] survived. This dramatic extinction pattern at the end of the Mesozoic led into the Cenozoic. Mammals and birds filled the empty niches left behind by the reptilian megafauna and, while reptile diversification slowed, bird and mammal diversification took an exponential turn.<ref name=Sahney-Benton-Ferry-2010/> However, reptiles were still important components of the megafauna, particularly in the form of large and giant [[tortoise]]s.<ref name=Hansen>{{cite journal |author1=Hansen, D.M. |author2=Donlan, C.J. |author3=Griffiths, C.J. |author4=Campbell, K.J. |date=April 2010 |title=Ecological history and latent conservation potential: Large and giant tortoises as a model for taxon substitutions |journal=[[Ecography (journal)|Ecography]] |volume=33 |issue=2 |pages=272–284 |doi=10.1111/j.1600-0587.2010.06305.x |bibcode=2010Ecogr..33..272H |doi-access=free}}</ref><ref name="Cione">{{cite journal |last=Cione |first=A.L. |author2=Tonni, E.P. |author3=Soibelzon, L. |year=2003 |title=The broken zig-zag: Late Cenozoic large mammal and tortoise extinction in South America |journal=Rev. Mus. Argentino Cienc. Nat. |series=N.S. |volume=5 |issue=1 |pages=1–19 |doi=10.22179/REVMACN.5.26 |doi-access=free }}</ref>

After the extinction of most archosaur and marine reptile lines by the end of the Cretaceous, reptile diversification continued throughout the Cenozoic. [[Squamata|Squamates]] took a massive hit during the K–Pg event, only recovering ten million years after it,<ref name=LBG12>{{cite journal | last1 = Longrich | first1 = Nicholas R. | last2 = Bhullar | first2 = Bhart-Anjan S. | last3 = Gauthier | first3 = Jacques A. | year = 2012 | title = Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 52 | pages = 21396–21401 | doi = 10.1073/pnas.1211526110 |doi-access=free| pmid=23236177 | pmc=3535637| bibcode = 2012PNAS..10921396L }}</ref> but they underwent a great radiation event once they recovered, and today squamates make up the majority of living reptiles (> 95%).<ref name="The Reptile Database">{{cite web |title = The Reptile Database |url = http://www.reptile-database.org/ |access-date = February 23, 2016}}</ref><ref>{{cite journal |author1=Reeder, Tod W. |author2=Townsend, Ted M. |author3=Mulcahy, Daniel G. |author4=Noonan, Brice P. |author5=Wood, Perry L. Jr. |author6=Sites, Jack W. Jr. |author7=Wiens, John J. |year=2015 |title=Integrated analyses resolve conflicts over squamate reptile phylogeny and reveal unexpected placements for fossil taxa |journal=[[PLOS One]] |volume=10 |issue=3 |page=e0118199 |pmid=25803280 |pmc=4372529 |doi=10.1371/journal.pone.0118199 |doi-access=free |bibcode=2015PLoSO..1018199R }}</ref> Approximately 10,000 extant species of traditional reptiles are known, with birds adding about 10,000 more, almost twice the number of mammals, represented by about 5,700&nbsp;living species (excluding [[List of domesticated animals|domesticated]] species).<ref>{{cite report |section=Numbers of threatened species by major groups of organisms (1996–2012) |title=[[IUCN Red List]] |year=2010 |publisher=[[International Union for Conservation of Nature|IUCN]] |section-url=http://www.iucnredlist.org/documents/summarystatistics/2012_1_RL_Stats_Table_1.pdf |access-date=January 30, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130204111508/http://www.iucnredlist.org/documents/summarystatistics/2012_1_RL_Stats_Table_1.pdf |archive-date=February 4, 2013 }}</ref>

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Species diversity of living reptiles (2013)<ref name=":0">{{Cite journal|last1=Pincheira-Donoso|first1=Daniel|last2=Bauer|first2=Aaron M.|last3=Meiri|first3=Shai|last4=Uetz|first4=Peter|date=2013-03-27|title=Global Taxonomic Diversity of Living Reptiles|journal=PLOS ONE|volume=8|issue=3|pages=e59741|bibcode=2013PLoSO...859741P|doi=10.1371/journal.pone.0059741|issn=1932-6203|pmc=3609858|pmid=23544091|doi-access=free}}</ref>
!Reptile group
!Described species
!Percent of reptile species
|-
|Squamates
|9193
|96.3%
|-
|''- Lizards''
|''5634''
|''59%''
|-
|''- Snakes''
|''3378''
|''35%''
|-
|''- Amphisbaenians''
|''181''
|''2%''
|-
|Turtles
|327
|3.4%
|-
|Crocodilians
|25
|0.3%
|-
|Rhynchocephalians
|1
|0.01%
|-
|Total
|9546
|100%
|}