Editing Reptile (section)

{{Short description|Class of animals}}
{{About|the animal class}}
{{pp-pc|small=yes}}
{{automatic taxobox
| name = Reptiles
| fossil_range = {{fossil range|Late Carboniferous|Present|ref=<ref name=M2021>{{cite journal|last1=Marjanović|first1=D.|year=2021|title=The Making of Calibration Sausage Exemplified by Recalibrating the Transcriptomic Timetree of Jawed Vertebrates|journal=Frontiers in Genetics|volume=12|at=521693|doi=10.3389/fgene.2021.521693|doi-access=free |pmid=34054911 |pmc=8149952 }}</ref>}}
| image = {{Multiple image
| perrow            = 2/2
| total_width       = 275
| caption_align     = center
| image1            =  TWC Wildlife Centre• Stewart Nimmo • MRD 8910.jpg
| caption1          = [[Tuatara]]
| image2            = SaltwaterCrocodile('Maximo').jpg
| caption2          = [[Saltwater crocodile]]
| image3            = Florida Box Turtle Digon3.jpg
| caption3          = [[Common box turtle]]
| image4            = Rhinechis scalaris cropped.jpg
| caption4          = [[Ladder snake]]
| border            = infobox
}}
| taxon = Reptilia
| authority = [[Josephus Nicolaus Laurenti|Laurenti]], 1768
| subdivision_ranks = Extant groups
| subdivision = * [[Lepidosauria]]
** [[Rhynchocephalia]]  {{small|([[tuatara]] and relatives)}}
** [[Squamata]] {{small|([[lizard]]s and [[snake]]s)}}
*[[Archelosauria]]
** [[Turtle|Testudines]] {{small|(turtles)}}
** [[Archosauria]]
*** [[Crocodilia]]
*** [[Dinosauria]]  {{small|(dinosaurs)}}
**** [[Aves]] {{small|(birds, cladistically included)}}

{{small|See [[#Taxonomy|text]] for extinct groups.}}
| range_map = 
| range_map_caption = Global reptile species distribution
}}

'''Reptiles''', as commonly defined,<!-- We are not employing the cladistic definition in the common definition of reptile --> are a group of [[tetrapod]]s with an [[ectotherm]]ic ('cold-blooded') [[metabolism]] and [[Amniotic egg|amniotic development]]. Living traditional reptiles comprise four [[Order (biology)|orders]]: Testudines ([[turtle]]s), Crocodilia ([[crocodilia]]ns), [[Squamata]] ([[lizard]]s and [[snake]]s), and [[Rhynchocephalia]] (the [[tuatara]]). As of May 2023, about 12,000 living species of reptiles are listed in the [[Reptile Database]].<ref>{{cite web |title=Reptile Database News |url=http://www.reptile-database.org/db-info/news.html |access-date=2022-05-25 |website=reptile-database.org}}</ref> The study of the traditional reptile orders, customarily in combination with the study of modern [[amphibian]]s, is called [[herpetology]].

Reptiles have been subject to several conflicting [[Taxonomy|taxonomic]] definitions.<ref name="modestoanderson2004" /> In [[Linnaean taxonomy]], reptiles are gathered together under the [[Class (biology)|class]] '''Reptilia''' ({{IPAc-en|r|E|p|'|t|I|l|i|ə}} {{respell|rep|TIL|ee|ə}}), which corresponds to common usage. Modern [[Cladistics|cladistic taxonomy]] regards that group as [[Paraphyly|paraphyletic]], since [[Genetics|genetic]] and [[Paleontology|paleontological]] evidence has determined that [[bird]]s (class Aves), as members of [[Dinosauria]], are more closely related to living crocodilians than to other reptiles, and are thus nested among reptiles from an evolutionary perspective. Many cladistic systems therefore redefine Reptilia as a [[clade]] ([[Monophyly|monophyletic]] group) including birds, though the precise definition of this clade varies between authors.<ref name="Gauthier-1994-Prothero-Schoch" /><ref name="modestoanderson2004" /> Others prioritize the clade [[Sauropsida]], which typically refers to all [[amniote]]s more closely related to modern reptiles than to [[mammal]]s.<ref name="Gauthier-1994-Prothero-Schoch" />

The earliest known proto-reptiles originated from the [[Carboniferous]] period, having evolved from advanced [[Reptiliomorpha|reptiliomorph]] tetrapods which became increasingly adapted to life on dry land. The earliest known [[Eureptilia|eureptile]] ("true reptile") was ''[[Hylonomus]]'', a small and superficially lizard-like animal which lived in [[Nova Scotia]] during the [[Bashkirian]] age of the [[Late Carboniferous]], around {{Ma|318}}.<ref name=M2021/> Genetic and fossil data argues that the two largest lineages of reptiles, [[Archosauromorpha]] (crocodilians, birds, and kin) and [[Lepidosauromorpha]] (lizards, and kin), diverged during the [[Permian]] period.<ref>{{cite journal |last1=Ezcurra |first1=M.D. |last2=Scheyer |first2=T.M. |last3=Butler |first3=R.J. |year=2014 |title=The origin and early evolution of Sauria: Reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence |journal=PLOS ONE |volume=9 |issue=2 |page=e89165 |doi=10.1371/journal.pone.0089165 |doi-access=free |pmc=3937355 |pmid=24586565 |bibcode=2014PLoSO...989165E}}</ref> In addition to the living reptiles, there are many diverse groups that are now [[extinction|extinct]], in some cases due to [[extinction event|mass extinction events]]. In particular, the [[Cretaceous–Paleogene extinction event]] wiped out the [[pterosaur]]s, [[Plesiosauria|plesiosaurs]], and all non-avian [[dinosaurs]] alongside many species of [[Crocodyliformes|crocodyliforms]] and [[Squamata|squamates]] (e.g., [[mosasaur]]s). Modern non-bird reptiles inhabit all the continents except Antarctica.

Reptiles are tetrapod [[vertebrates]], creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike [[amphibian]]s, reptiles do not have an aquatic larval stage. Most reptiles are [[oviparous]], although several species of squamates are [[viviparity|viviparous]], as were some extinct aquatic clades<ref name=S12>{{cite journal |last=Sander |first=P. Martin |year=2012 |title=Reproduction in early amniotes |journal=Science |volume=337 |issue=6096 |pages=806–808 |doi=10.1126/science.1224301 |pmid=22904001 |bibcode=2012Sci...337..806S |s2cid=7041966 }}</ref>  – the fetus develops within the mother, using a [[Placentation#In lizards and snakes|(non-mammalian) placenta]] rather than contained in an [[eggshell]]. As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their [[fetus]]es through various forms of placenta analogous to those of [[mammal]]s, with some providing initial care for their hatchlings. [[neontology|Extant]] reptiles range in size from a tiny gecko, ''[[Sphaerodactylus ariasae]]'', which can grow up to {{convert|17|mm|in|1|abbr=on}} to the [[saltwater crocodile]], ''Crocodylus porosus'', which can reach over {{convert|6|m|ft|1|abbr=on}} in length and weigh over {{convert|1000|kg|lb|abbr=on}}.