{{Short description|Superorder of reptiles}} {{Automatic taxobox | fossil_range = <br />Middle Triassic - Present, {{Fossil range|244|0}} | image = Lepidosauria Diversity.jpg | image_upright = 1.2 | image_caption = Collage of five lepidosaurs. Clockwise from top left: tuatara, black mamba, green iguana, ''Smaug breyeri'' and reticulated python | taxon = Lepidosauria | authority = Haeckel, 1866 | subdivision_ranks = Orders and genera | subdivision = *Rhynchocephalia *{{extinct}}''Vellbergia''? *'''Pan-Squamata''' **{{extinct}}''Sophineta''? **{{extinct}}''Megachirella''? **{{extinct}}''Marmoretta''? **{{extinct}}''Tamaulipasaurus''? **{{extinct}}''Hongshanxi'' **{{extinct}}''Bellairsia'' **{{extinct}}''Oculudentavis'' **{{extinct}}''Huehuecuetzpalli'' **{{extinct}}Parviraptoridae? **Squamata }}
The '''Lepidosauria''' ({{IPAc-en|,|l|E|p|ᵻ|d|ou|'|s|ɔː|r|i|@}}, from Greek meaning ''scaled lizards'') is a superorder<ref>{{Cite journal |last=Herrera-Flores |first=Jorge A. |last2=Stubbs |first2=Thomas L. |last3=Elsler |first3=Armin |last4=Benton |first4=Michael J. |date=2018-04-06 |title=Taxonomic reassessment of Clevosaurus latidens Fraser, 1993 (Lepidosauria, Rhynchocephalia) and rhynchocephalian phylogeny based on parsimony and Bayesian inference |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/taxonomic-reassessment-of-clevosaurus-latidens-fraser-1993-lepidosauria-rhynchocephalia-and-rhynchocephalian-phylogeny-based-on-parsimony-and-bayesian-inference/AEED7FE732081A56AD8B02CB57451716 |journal=Journal of Paleontology |language=en |volume=92 |issue=4 |pages=734–742 |doi=10.1017/jpa.2017.136 |issn=0022-3360|doi-access=free |hdl=1983/59126b60-16d8-46d2-b657-954693a39d4e |hdl-access=free }}</ref> of reptiles, containing the orders Squamata and Rhynchocephalia.<ref>{{cite journal | last1 = Pyron | first1 = RA | last2 = Burbrink | first2 = FT | last3 = Wiens | first3 = JJ | year = 2013| title = A phylogeny and revised classification of Squamata, including 4,161 species of lizards and snakes | journal = BMC Evolutionary Biology | volume = 13 | issue = 1 | page = 93 | doi=10.1186/1471-2148-13-93 | pmid=23627680 | pmc=3682911 | doi-access = free | bibcode = 2013BMCEE..13...93P }}</ref> Squamata, comprising lizards and snakes, contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day.<ref>{{cite journal |last1=Uetz |first1=Peter |title=The original descriptions of reptiles |journal=Zootaxa |date=13 January 2010 |volume=2334 |issue=1 |pages=59–68 |doi=10.11646/zootaxa.2334.1.3 |doi-access=free }}</ref> Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era.<ref>{{cite journal |last1=Jones |first1=M.E.H. |title=Dentary Tooth Shape in Sphenodon and Its Fossil Relatives (Diapsida: Lepidosauria: Rhynchocephalia) |journal=Frontiers of Oral Biology |date=2009 |volume=13 |pages=9–15 |doi=10.1159/000242382 |pmid=19828962 |isbn=978-3-8055-9229-1 }}</ref> However, it is represented by only one living species: the tuatara (''Sphenodon punctatus),'' a superficially lizard-like reptile native to New Zealand.<ref name="Hay et al 2010">{{cite journal |last1=Hay |first1=Jennifer M. |last2=Sarre |first2=Stephen D. |last3=Lambert |first3=David M. |last4=Allendorf |first4=Fred W. |last5=Daugherty |first5=Charles H. |title=Genetic diversity and taxonomy: a reassessment of species designation in tuatara (''Sphenodon'': Reptilia) |journal=Conservation Genetics |date=June 2010 |volume=11 |issue=3 |pages=1063–1081 |doi=10.1007/s10592-009-9952-7 |bibcode=2010ConG...11.1063H |hdl= 10072/30480 |s2cid=24965201 |hdl-access=free }}</ref><ref>{{cite journal | last1 = Jones | first1 = M.E.H. | last2 = Cree | first2 = A. | year = 2012 | title = Tuatara | journal = Current Biology | volume = 22 | issue = 23| pages = 986–987 | doi = 10.1016/j.cub.2012.10.049 | pmid = 23218010 | doi-access = free | bibcode = 2012CBio...22.R986J }}</ref>
Lepidosauria is a monophyletic group (i.e. a clade), containing all descendants of the last common ancestor of squamates and rhynchocephalians.<ref>{{cite book | last1 = Evans | first1 = S.E. | last2 = Jones | first2 = M.E.H. | year = 2010 | chapter= The Origin, early history and diversification of lepidosauromorph reptiles |editor=Bandyopadhyay, S. |title=New Aspects of Mesozoic Biodiversity | series =Lecture Notes in Earth Sciences | volume = 132 | pages = 27–44 | doi = 10.1007/978-3-642-10311-7_2 | isbn = 978-3-642-10310-0 }}</ref> Lepidosaurs can be distinguished from other reptiles via several traits, such as large keratinous scales which may overlap one another. Purely in the context of modern taxa, Lepidosauria can be considered the sister taxon to Archelosauria, which includes Testudines (turtles), Aves (birds) and Crocodilia (crocodilians). Lepidosauria is encompassed by Lepidosauromorpha, a broader group defined as all reptiles (living or extinct) closer to lepidosaurs than to archosaurs.
==Evolution== Lepidosauromorpha is thought to have split from their sister group, Archelosauria, during the Permian period.<ref>{{Cite journal |last1=Simões |first1=T. R. |last2=Kammerer |first2=C. F. |last3=Caldwell |first3=M. W. |last4=Pierce |first4=S. E. |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 |article-number=eabq1898 |doi=10.1126/sciadv.abq1898 |pmc=9390993 |pmid=35984885 |doi-access=free|bibcode=2022SciA....8.1898S }}</ref> The earliest members of Lepidosauromorpha date to the Early Triassic. The oldest known definitive lepidosaur is the rhynchocephalian ''Agriodontosaurus'' from the Helsby Sandstone Formation of the United Kingdom, dating to the upper Anisian stage of the Middle Triassic, approximately {{Ma|244|241.5}}.<ref>{{Cite journal |last=Marke |first=Daniel |last2=Whiteside |first2=David I. |last3=Sethapanichsakul |first3=Thitiwoot |last4=Coram |first4=Robert A. |last5=Fernandez |first5=Vincent |last6=Liptak |first6=Alexander |last7=Newham |first7=Elis |last8=Benton |first8=Michael J. |date=2025-09-10 |title=The oldest known lepidosaur and origins of lepidosaur feeding adaptations |journal=Nature |language=en |pages=1–10 |doi=10.1038/s41586-025-09496-9 |issn=1476-4687 |doi-access=free|pmc=12629995 }}</ref> The next earliest rhynchocephalian, ''Wirtembergia'', is known from the Ladinian stage of the Middle Triassic.<ref name=":9">{{Cite journal |last1=Sues |first1=Hans-Dieter |last2=Schoch |first2=Rainer R. |date=2023-11-07 |title=The oldest known rhynchocephalian reptile from the Middle Triassic (Ladinian) of Germany and its phylogenetic position among Lepidosauromorpha |url=https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25339 |journal=The Anatomical Record |volume=307 |issue=4 |pages=776–790 |language=en |doi=10.1002/ar.25339 |pmid=37937325 |s2cid=265050255 |issn=1932-8486|url-access=subscription }}</ref> ''Sophineta'' is known from older rocks in the Early Triassic, but its exact placement within the broader clade Lepidosauromorpha is uncertain and it may not be a true lepidosaur.<ref name=":0">{{Cite journal |last1=Ford |first1=David P. |last2=Evans |first2=Susan E. |last3=Choiniere |first3=Jonah N. |last4=Fernandez |first4=Vincent |last5=Benson |first5=Roger B. J. |date=2021-08-25 |title=A reassessment of the enigmatic diapsid Paliguana whitei and the early history of Lepidosauromorpha |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=288 |issue=1957 |article-number=20211084 |doi=10.1098/rspb.2021.1084 |issn=0962-8452 |pmc=8385343 |pmid=34428965}}</ref> While the lepidosaur ''Megachirella'' may represent a stem-group squamate from the Middle Triassic,<ref>{{Cite journal |last1=Simōes |first1=Tiago R. |last2=Caldwell |first2=Michael W. |last3=Talanda |first3=Mateusz |last4=Bernardi |first4=Massimo |last5=Palci |first5=Alessandro |last6=Vernygora |first6=Oksana |last7=Bernardini |first7=Federico |last8=Mancini |first8=Lucia |last9=Nydam |first9=Randall L. |date=30 May 2018 |title=The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps |journal=Nature |volume=557 |issue=7707 |pages=706–709 |bibcode=2018Natur.557..706S |doi=10.1038/s41586-018-0093-3 |pmid=29849156 |s2cid=44108416}}</ref> the earliest modern members of the group are known from the Middle Jurassic.<ref>{{Cite journal |last=Rage |first=Jean-Claude |date=December 2013 |title=Mesozoic and Cenozoic squamates of Europe |url=https://link.springer.com/10.1007/s12549-013-0124-x |journal=Palaeobiodiversity and Palaeoenvironments |language=en |volume=93 |issue=4 |pages=517–534 |doi=10.1007/s12549-013-0124-x |bibcode=2013PdPe...93..517R |s2cid=128588324 |issn=1867-1594|url-access=subscription }}</ref> Squamates underwent a great radiation in the Cretaceous,<ref>{{Cite journal |last1=Herrera-Flores |first1=Jorge A. |last2=Stubbs |first2=Thomas L. |last3=Benton |first3=Michael J. |date=March 2021 |title=Ecomorphological diversification of squamates in the Cretaceous |journal=Royal Society Open Science |language=en |volume=8 |issue=3 |article-number=rsos.201961 |doi=10.1098/rsos.201961 |doi-access=free|issn=2054-5703 |pmc=8074880 |pmid=33959350|bibcode=2021RSOS....801961H }}</ref> while rhynchocephalians declined during the same time period.<ref>{{Cite journal |last1=Anantharaman |first1=S. |last2=DeMar |first2=David G. |last3=Sivakumar |first3=R. |last4=Dassarma |first4=Dilip Chandra |last5=Wilson Mantilla |first5=Gregory P. |last6=Wilson Mantilla |first6=Jeffrey A. |date=2022-06-30 |title=First rhynchocephalian (Reptilia, Lepidosauria) from the Cretaceous–Paleogene of India |journal=Journal of Vertebrate Paleontology |language=en |volume=42 |issue=1 |doi=10.1080/02724634.2022.2118059 |issn=0272-4634|doi-access=free |bibcode=2022JVPal..42E8059A }}</ref>
==Description== Extant reptiles are in the clade Diapsida, named for the two pairs of temporal fenestrae present on the skull behind the eye socket.<ref name="Romer & Parson">{{cite book |last1=Romer |first1=Alfred Sherwood |author-link1=Alfred Romer |last2=Parsons |first2=Thomas Sturges |title=The Vertebrate Body |date=1986 |publisher=Saunders |isbn=978-0-03-058446-6 }}{{pn|date=August 2020}}</ref> Until recently, Diapsida was said to be composed of Lepidosauria and their sister taxa Archosauria.<ref name="ref2">{{cite book |last1=Pough |first1=F. Harvey |title=Herpetology |last2=Andrews |first2=Robin M. |last3=Cadle |first3=John E. |last4=Crump |first4=Martha L. |last5=Savitzky |first5=Alan H. |last6=Wells |first6=Kentwood D. |date=1998 |publisher=Prentice Hall |isbn=978-0-13-850876-0}}{{pn|date=August 2020}}</ref> The Lepidosauria is then split into Squamata<ref name="pmid25803280">{{cite journal |last1=Reeder |first1=Tod W. |last2=Townsend |first2=Ted M. |last3=Mulcahy |first3=Daniel G. |last4=Noonan |first4=Brice P. |last5=Wood |first5=Perry L. |last6=Sites |first6=Jack W. |last7=Wiens |first7=John J. |title=Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa |journal=PLOS ONE |date=24 March 2015 |volume=10 |issue=3 |article-number=e0118199 |doi=10.1371/journal.pone.0118199 |pmid=25803280 |pmc=4372529 |bibcode=2015PLoSO..1018199R |doi-access=free }}</ref> and Rhynchocephalia. More recent morphological studies<ref name="Rieppel">{{cite journal | last1 = Rieppel | first1 = O. | year = 1996 | last2 = DeBraga | first2 = M. | title = Turtles as diapsid reptiles | journal = Nature | volume = 384 | issue = 6608 | pages = 453–5 | doi = 10.1038/384453a0 | bibcode = 1996Natur.384..453R| s2cid = 4264378 | url = https://doc.rero.ch/record/16242/files/PAL_E3477.pdf }}</ref><ref name="Muller2004">{{cite book | last = Müller | first = Johannes | year = 2004 | chapter = The relationships among diapsid reptiles and the influence of taxon selection |chapter-url=https://www.pfeil-verlag.de/wp-content/uploads/2015/05/3_52d17.pdf | editor1-last = Arratia | editor1-first = G | editor2-last = Wilson | editor2-first = M.V.H. | editor3-last = Cloutier | editor3-first = R. | title = Recent Advances in the Origin and Early Radiation of Vertebrates | publisher = Verlag Dr. Friedrich Pfeil | pages = 379–408 | isbn = 978-3-89937-052-2 }}</ref> and molecular studies<ref name="Mannen">{{Cite journal|last = Mannen|first = Hideyuki|author2=Li, Steven S. -L. |title = Molecular evidence for a clade of turtles|journal = Molecular Phylogenetics and Evolution|volume = 13|issue = 1|pages = 144–148| date = Oct 1999|doi = 10.1006/mpev.1999.0640 | pmid = 10508547| bibcode=1999MolPE..13..144M }}</ref><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=Proc Natl Acad Sci U S A| issn=0027-8424| volume=95| issue=24| pages=14226–14231| doi=10.1073/pnas.95.24.14226| pmid=9826682| pmc=24355| bibcode=1998PNAS...9514226Z| doi-access=free}}</ref><ref name="Iwabe">{{Cite journal | last = Iwabe | first = N. |author2=Hara, Y.|author3=Kumazawa, Y.|author4=Shibamoto, K.|author5=Saito, Y.|author6=Miyata, T.|author7= Katoh, K. | 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 | date = 2004-12-29 | doi = 10.1093/molbev/msi075 | pmid = 15625185 | doi-access = free }}</ref><ref name="Roos">{{Cite journal | last = Roos | first = Jonas |author2= Aggarwal, Ramesh K.|author3= Janke, Axel | 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 | date = Nov 2007 | doi = 10.1016/j.ympev.2007.06.018 | pmid = 17719245| bibcode = 2007MolPE..45..663R }}</ref><ref name="Katsu">{{Cite journal | last = Katsu | first = Y. |author2= Braun, E. L.|author3= Guillette, L. J. Jr.|author4= Iguchi, 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><ref name="Lyson2012">{{Cite journal |author1=Tyler R. Lyson |author2=Erik A. Sperling |author3=Alysha M. Heimberg |author4=Jacques A. Gauthier |author5=Benjamin L. King |author6=Kevin J. Peterson | title = MicroRNAs support a turtle + lizard clade | journal = Biology Letters | volume = 8 | issue = 1 | pages = 104–107 | doi = 10.1098/rsbl.2011.0477 | pmid=21775315 | pmc=3259949|date=2012-02-23 |bibcode=2012BiLet...8..104L }}</ref>{{excessive citations inline|date=June 2025}} also place turtles firmly within Diapsida, even though they lack temporal fenestrations. [[File:Serpiente en el parque de Jaraguá 2.jpg|thumb|The quadrate bone is particularly elongated in snakes, to facilitate cranial kinesis]] The reptiles in the Lepidosauria can be distinguished from other reptiles by a variety of characteristics.<ref>{{cite journal |last1=Evans |first1=S.E. |year=2003 |title=At the feet of the dinosaurs: the early history and radiation of lizards |url=http://pdfs.semanticscholar.org/1c60/a5f91d80e99f94a84c54363a882fb6f9c187.pdf |journal=Biological Reviews |volume=78 |issue=4 |pages=513–551 |doi=10.1017/S1464793103006134 |pmid=14700390 |s2cid=4845536 |archive-url=https://web.archive.org/web/20190219175746/http://pdfs.semanticscholar.org/1c60/a5f91d80e99f94a84c54363a882fb6f9c187.pdf |archive-date=2019-02-19}}</ref> Lepidosaurs are suggested to be distinguished from more primitive lepidosauromorphs by the development of a conch on the quadrate, allowing for the development of a tympanic membrane in the ear (a trait lost in the tuatara, but present in early rhynchocephalians), as well as the development of a subolfactory process on the frontal bones of the skull.<ref name=":0" /><ref>{{Citation |last=Evans |first=Susan E. |title=The Lepidosaurian Ear: Variations on a Theme |date=2016 |url=https://link.springer.com/10.1007/978-3-319-46661-3_9 |work=Evolution of the Vertebrate Ear |series=Springer Handbook of Auditory Research |volume=59 |pages=245–284 |editor-last=Clack |editor-first=Jennifer A. |access-date=2024-01-08 |place=Cham |publisher=Springer International Publishing |doi=10.1007/978-3-319-46661-3_9 |isbn=978-3-319-46659-0 |editor2-last=Fay |editor2-first=Richard R |editor3-last=Popper |editor3-first=Arthur N.|url-access=subscription }}</ref> [[File:Skull squamata 1.png|thumb|left|Schematic skull of a squamate showing the location of major dermal bones]] The group Squamata<ref name="pmid25803280" /> includes snakes, lizards, and amphisbaenians. Squamata can be characterized by the reduction or loss of limbs. Snakes and legless lizards have evolved the complete loss of their limbs. The upper jaw of Squamates is movable on the cranium, a configuration called kinesis.<ref name="refthree">{{cite book |last1=Bellairs |first1=Angus d'A |title=Reptiles life history, evolution, and structure. |date=1960 |publisher=Harper |oclc=692993911 |author-link1=Angus Bellairs}}{{pn|date=August 2020}}</ref> This is made possible by a loose connection between the quadrate and its neighboring bones.<ref name="ref4">{{cite book |last1=Benton |first1=M. J |title=The Phylogeny and classification of the tetrapods |date=1988 |publisher=Oxford |oclc=681456805}}{{pn|date=August 2020}}</ref> Without this, snakes would not be able consume prey that are much larger than themselves. Amphisbaenians are mostly legless like snakes, but are generally much smaller. Three species of amphisbaenians have kept reduced front limbs and these species are known for actively burrowing in the ground.<ref name="pmid19281946">{{cite journal |last1=Vidal |first1=Nicolas |last2=Hedges |first2=S. Blair |date=February 2009 |title=The molecular evolutionary tree of lizards, snakes, and amphisbaenians |url=https://comptes-rendus.academie-sciences.fr/biologies/articles/10.1016/j.crvi.2008.07.010/ |journal=Comptes Rendus Biologies |volume=332 |issue=2–3 |pages=129–139 |doi=10.1016/j.crvi.2008.07.010 |pmid=19281946 |s2cid=23137302|url-access=subscription }}</ref> The tuatara and some extinct rhynchocephalians have a more rigid skull with a complete lower temporal bar closing the lower temporal fenestra formed by the fusion of the jugal and quadrate/quadratojugal bones, similar to the condition found in primitive diapsids. However early rhynchocephalians and lepidosauromorphs had an open lower temporal fenestra, without a complete temporal bar, so this is thought to be a reversion rather than retention. The temporal bar is thought to stabilise the skull during biting.<ref name=":02">{{Cite journal |last1=Simões |first1=Tiago R. |last2=Kinney-Broderick |first2=Grace |last3=Pierce |first3=Stephanie E. |date=2022-03-03 |title=An exceptionally preserved Sphenodon-like sphenodontian reveals deep time conservation of the tuatara skeleton and ontogeny |journal=Communications Biology |language=en |volume=5 |issue=1 |page=195 |doi=10.1038/s42003-022-03144-y |issn=2399-3642 |pmc=8894340 |pmid=35241764}}</ref>
Male squamates have evolved a pair of hemipenises instead of a single penis with erectile tissue that is found in crocodilians, birds, mammals, and turtles. The hemipenis can be found in the base of the tail. The tuatara does not have a hemipenis, but instead has shallow paired outpocketings of the posterior wall of the cloaca.<ref name="ref2" />[[File:Katoomba-Hand-of-skink-edited.jpg|thumb|left|The foot of a skink, showing lepidosaurs' characteristic overlapping scales]]Second, most lepidosaurs have the ability to autotomize their tails. However, this trait has been lost on some recent species. In lizards and rhynchocephalians, fracture planes are present within the vertebrae of the tail that allow for its removal. Some lizards have multiple fracture planes, while others just have a single fracture plane. The regrowth of the tail is not always complete and is made of a solid rod of cartilage rather than individual vertebrae.<ref name="ref2" /> In snakes, the tail separates between vertebrae and some do not experience regrowth.<ref name="ref2" />
Third, the scales in lepidosaurs are horny (keratinized) structures of the epidermis, allowing them to be shed collectively, contrary to the scutes seen in other reptiles.<ref name="ref2"/> This is done in different cycles, depending on the species. However, lizards generally shed in flakes while snakes shed in one piece. Unlike scutes, lepidosaur scales will often overlap like roof tiles.
==Biology and ecology== [[File:The Pit Organs of Two Different Snakes.jpg|thumb|Python (top) and rattlesnake (bottom) featuring pit organs for infrared sensing. Red arrows indicating pit organs and black arrows pointing to the nostrils]] Squamates are represented by viviparous, ovoviviparous, and oviparous species. Viviparous means that the female gives birth to live young, Ovoviviparous means that the egg will develop inside the female's body and Oviparous means that the female lays eggs. A few species within Squamata have the ability to reproduce asexually.<ref name="ref6">{{cite journal | last1 = Smith | first1 = James G | year = 2010 | title = Survival estimation in a long-lived monitor lizard: radio-tracking of ''Varanus mertensi'' | journal = Population Ecology | volume = 52 | issue = 1 | pages = 243–247 | doi=10.1007/s10144-009-0166-0| bibcode = 2010PopEc..52..243S | s2cid = 43055329 }}</ref> The tuatara lays eggs that are usually about one inch in length and which take about 14 months to incubate.<ref name="refthree"/>
While in the egg, the Squamata embryo develops an egg tooth on the premaxillary that helps the animal emerge from the egg.<ref name="ref5">{{cite book |last1=Zug |first1=George R. |title=Herpetology: An Introductory Biology of Amphibians and Reptiles |date=1993 |publisher=Academic Press |isbn=978-0-12-782620-2}}{{pn|date=August 2020}}</ref> A reptile will increase three to twentyfold in length from hatching to adulthood.<ref name="ref5"/> There are three main life history events that lepidosaurs reach: hatching/birth, sexual maturity, and reproductive senility.<ref name="ref5"/>
Because gular pumping is so common in squamates, and is also found in the tuatara, it is assumed that it is an original trait in the group.<ref>[https://www.brown.edu/Departments/EEB/brainerd_lab/pdf/Brainerd_and_Owerkowicz_2006.pdf Functional morphology and evolution of aspiration breathing in tetrapods]</ref>
Most lepidosaurs rely on camouflage as one of their main defenses. Some species have evolved to blend in with their ecosystem, while others are able to change their skin color to blend in with their current surroundings. The ability to autotomize the tail is another defense that is common among lepidosaurs. Other species, such as the Echinosauria, have evolved the defense of feigning death.<ref name="ref5"/>
===Hunting and diet=== [[File:Bronchocela sp.jpg|thumb|left|A green crested lizard feeding on an invertebrate]] Viperines can sense their prey's infrared radiation through bare nerve endings on the skin of their heads.<ref name="ref5"/> Also, viperines and some boids have thermal receptors that allow them to target their prey's heat.<ref name="ref5"/> Many snakes are able to obtain their prey through constriction. This is done by first biting the prey, then coiling their body around the prey. The snake then tightens its grip as the prey struggles, which leads to suffocation.<ref name="ref5"/> Some snakes have fangs that produce venomous bites, which allows the snake to consume unconscious, or even dead, prey. Also, some venoms include a proteolytic component that aids in digestion.<ref name="ref5"/> Chameleons grasp their prey with a projectile tongue. This is made possible by a hyoid mechanism, which is the contraction of the hyoid muscle that drives the tip of the tongue outwards.<ref name="ref5"/> [[File:Eastern Brown Snake eating an Eastern Blue tongue. (8235991265).jpg|thumb|An eastern blue-tongued lizard preyed upon by an eastern brown snake]] Within the Lepidosauria there are herbivores, omnivores, insectivores, and carnivores. The herbivores consist of iguanines, some agamids, and some skinks.<ref name="ref5"/> Most lizard species and some snake species are insectivores. The remaining snake species, tuataras, and amphisbaenians, are carnivores. While some snake species are generalist, others eat a narrow range of prey - for example, Salvadora only eat lizards.<ref name="ref5"/> The remaining lizards are omnivores and can consume plants or insects. The broad carnivorous diet of the tuatara may be facilitated by its specialised shearing mechanism, which involves a forward movement of the lower jaw following jaw closure.<ref>{{cite journal | last1 = Jones | first1 = M.E.H. | last2 = O'Higgins | first2 = P. | last3 = Fagan | first3 = M. | last4 = Evans | first4 = S.E. | last5 = Curtis | first5 = N. | year = 2012 | title = Shearing mechanics and the influence of a flexible symphysis during oral food processing in Sphenodon (Lepidosauria: Rhynchocephalia) | journal = The Anatomical Record | volume = 295 | issue = 7| pages = 1075–1091 | doi = 10.1002/ar.22487 | pmid = 22644955 | s2cid = 45065504 | doi-access = free }}</ref>
While birds, including raptors, wading birds and roadrunners, and mammals are known to prey on reptiles, the major predator is other reptiles. Some reptiles eat reptile eggs, for example the diet of the Nile monitor includes crocodile eggs, and small reptiles are preyed upon by larger ones.<ref name="ref5"/>
==Conservation== [[File:Lizard range.png|thumb|left|Global range of lizard species]] The geographic ranges of lepidosaurs are vast and cover all but the most extreme cold parts of the globe. Amphisbaenians exist in Florida, mainland Mexico, including Baja California, the Mediterranean region, the Middle East, North Africa, sub-Saharan Africa, South America, and the Caribbean.<ref name="ref4"/> The tuatara is confined to only a few rocky islands of New Zealand, where it digs burrows to live in and preys mostly on insects.<ref name="refthree"/>
Climate change has led to the need for conservation efforts to protect the existence of the tuatara. This is because it is not possible for this species to migrate on its own to cooler areas. Conservationists are beginning to consider the possibility of translocating them to islands with cooler climates.<ref name="ref8">{{cite journal | last1 = Besson | first1 = A. A. | last2 = Cree | first2 = A. | year = 2011 | title = Integrating physiology into conservation: an approach to help guide translocations of a rare reptile in a warming environment | journal = Animal Conservation | volume = 14 | issue = 1 | pages = 28–37 | doi=10.1111/j.1469-1795.2010.00386.x| bibcode = 2011AnCon..14...28B | s2cid = 84015883 }}</ref> The range of the tuatara has already been minimized by the introduction of cats, rats, dogs, and mustelids to New Zealand.<ref name="ref9">{{cite journal | last1 = Nelson | first1 = Nicola J. | display-authors = etal | year = 2002 | title = Establishing a new wild population of tuatara (''Sphendon guntheri'') | journal = Conservation Biology | volume = 16 | issue = 4| pages = 887–894 | doi=10.1046/j.1523-1739.2002.00381.x| s2cid = 85262510 }}</ref> The eradication of the mammals from the islands where the tuatara still survives has helped the species increase its population. An experiment observing the tuatara population after the removal of the Polynesian rat showed that the tuatara expressed an island-specific increase of population after the rats' removal.<ref name="ref10">{{cite journal | last1 = Towns | first1 = David R | year = 2009 | title = Eradication as reverse invasion: lesions from Pacific Rat (Rattus exulans) removals on New Zealand islands | journal = Biol Invasions | volume = 11 | issue = 7| pages = 1719–1733 | doi=10.1007/s10530-008-9399-7| bibcode = 2009BiInv..11.1719T | s2cid = 44200993 }}</ref> However, it may be difficult to keep these small mammals from reinhabiting these islands.
Habitat destruction is the leading negative impact of humans on reptiles. Humans continue to develop land that is important habitat for the lepidosaurs. The clear-cutting of land has also led to habitat reduction. Some snakes and lizards migrate toward human dwellings because there is an abundance of rodent and insect prey. However, these reptiles are seen as pests and are often exterminated.<ref name="ref2"/>
===Interactions with humans=== [[File:SnakeskinBoots1 gobeirne.jpg|thumb|Boots made from snake skin, the three closest from diamondback rattlesnakes]] Snakes are commonly feared throughout the world. Bounties were paid for dead cobras under the British Raj in India; similarly, there have been advertised rattlesnake roundups in North America. Data shows that between 1959 and 1986 an average of 5,563 rattlesnakes were killed per year in Sweetwater, Texas, due to rattlesnake roundups, and these roundups have led to documented declines and local extirpations of rattlesnake populations, especially Eastern Diamondbacks in Georgia.<ref name="ref2"/>
People have introduced species to the lepidosaurs' natural habitats that have increased predation on the reptiles. For example, mongooses were introduced to Jamaica from India to control the rat infestation in sugar cane fields. As a result, the mongooses fed on the lizard population of Jamaica, which has led to the elimination or decrease of many lizard species.<ref name="ref2"/> Actions can be taken by humans to help endangered reptiles. Some species are unable to be bred in captivity, but others have thrived. There is also the option of animal refuges. This concept is helpful to contain the reptiles and keep them from human dwellings. However, environmental fluctuations and predatorial attacks still occur in refuges.<ref name="ref5"/>
Reptile skins are still being sold. Accessories, such as shoes, boots, purses, belts, buttons, wallets, and lamp shades, are all made out of reptile skin.<ref name="ref2"/> In 1986, the World Resource Institute estimated that 10.5 million reptile skins were traded legally. This total does not include the illegal trades of that year.<ref name="ref2"/> Horned lizards are popularly harvested and stuffed.<ref name="ref2"/> Some humans are making a conscious effort to preserve the remaining species of reptiles, however.
==References== {{reflist|25em}}
==External links== {{Portal|Reptiles}} * [https://web.archive.org/web/20040417191214/http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Lepidosauria.html Animaldiversity.ummz.umich.edu] * [https://web.archive.org/web/20081019121413/http://palaeo.gly.bris.ac.uk/benton/vertclass.html#reptiles Reptile taxonomy, Benton 2004] * [https://web.archive.org/web/20060310195739/http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Reptilia/Lepidosauromorpha/Lepidosauriformes.htm Lepidosaur phylogeny]
{{Chordata}} {{Lepidosauromorpha}} {{Taxonbar|from=Q728299}}
Category:Lepidosauria Category:Chordate superorders Category:Ladinian first appearances Category:Extant Middle Triassic first appearances