Wikipedija mtwiki https://mt.wikipedia.org/wiki/Il-Pa%C4%A1na_prin%C4%8Bipali MediaWiki 1.46.0-wmf.24 first-letter Medja Speċjali Diskussjoni Utent Diskussjoni utent Wikipedija Diskussjoni Wikipedija Stampa Diskussjoni stampa MediaWiki Diskussjoni MediaWiki Mudell Diskussjoni mudell Għajnuna Diskussjoni għajnuna Kategorija Diskussjoni kategorija Portal Diskussjoni portal TimedText TimedText talk Module Module talk Event Event talk 0 34383 329560 329545 2026-04-27T07:10:27Z Trigcly 17859 /* Rettili Mesożojċi */ 329560 wikitext text/x-wiki {{Automatic taxobox}} '''Rettilu''', xi kultant imsejjaħ '''rettili''' b'mod invarjabbli bejn is-singular u l-plural, spiss jiġi definit bħala [[annimal]] vertebrat tetrapodu b'metaboliżmu ektotermiku u bi żvilupp amnijotiku. Tradizzjonalment ir-rettili huma magħmula minn erba' [[Ordni (bijoloġija)|ordnijiet]]: ''Testudines'' (fkieren), ''Crocodilia'' (kukkudrilli, alligaturi u garjal), ''Squamata'' (gremxul u [[Serp|sriep]]) u ''Rhynchocephalia'' (tuatara), b'madwar 12,000 [[speċi]] eżistenti fil-Bażi tad-Data tar-Rettili.<ref>{{Ċita web|url=http://www.reptile-database.org/db-info/news.html|titlu=Reptile Database News|sit=www.reptile-database.org|data-aċċess=2026-04-23}}</ref> L-istudju tal-ordnijiet tar-rettili tradizzjonali, normalment flimkien mal-istudju tal-[[Anfibju|anfibji]] moderni, jissejjaħ erpetoloġija.[[Stampa:TWC Wildlife Centre• Stewart Nimmo • MRD 8910.jpg|daqsminuri|Tuatara.]]Ir-rettili ġew soġġetti għal diversi definizzjonijiet tassonomiċi kunfliġġenti.<ref>Modesto, S.P.; Anderson, J.S. (2004). "The phylogenetic definition of Reptilia". ''Systematic Biology''. '''53''' (5): 815–821. doi:10.1080/10635150490503026. <nowiki>PMID 15545258</nowiki>.</ref> Fit-tassonomija evoluzzjonarja klassika, ir-rettili jinġabru taħt il-[[Klassi (bijoloġija)|klassi]] '''''Reptilia''''' (pronunzja: /rɛpˈtɪliə/ ''rep-TIL-ee-ə''), skont l-użu komuni. It-tassonomija kladistika moderna tqis lil dak il-grupp bħala parafiletiku, peress li l-evidenza ġenetika u paleontoloġika ddeterminat li l-[[Għasfur|għasafar]] (il-klassi ''Aves'') huma l-uniku grupp li għadu eżistenti ta' ''Dinosauria'', grupp monofiletiku ewlieni ta' diapsidi li huma relatati iktar mill-qrib mal-''Crocodilia'' milli ma rettili ħajjin oħra, u għaldaqstant l-għasafar jinsabu fost ir-rettili (taħt l-''Archosauria'') minn perspettiva filoġenetika. Għalhekk, bosta sistemi kladistiċi jiddefinixxi mill-ġdid ir-''Reptilia'' bħala grupp monofiletiku li jinkludi l-għasafar, għalkemm id-definizzjoni preċiża ta' dan il-grupp monofiletiku jvarja minn awtur għal ieħor. Kunċett simili huwa dak tal-grupp monofiletiku tas-''Sauropsida'', li jirreferi għall-amnijoti kollha bħala relatati iktar mill-qrib mar-rettili moderni milli mal-mammiferi.<ref>Gauthier, J.A. (1994). "The diversification of the amniotes". In Prothero, D.R.; Schoch, R.M. (eds.). ''Major Features of Vertebrate Evolution''. Vol. 7. Knoxville, TN: The Paleontological Society. pp. 129–159. doi:10.1017/S247526300000129X.</ref> L-iżjed membri bikrin magħrufa tan-nisel tar-rettili tfaċċaw matul il-perjodu Karboniferu aħħari, wara li evolvew minn tetrapodi rettilomorfi avvanzati li kulma jmur adattaw ruħhom iktar għall-ħajja fuq l-art niexfa.<ref>Reisz, R. R. (1981). ''A diapsid reptile from the Pennsylvanian of Kansas''. Natural History Museum, University of Kansas.</ref> Id-data ġenetika u tal-fossili ssostni li l-ikbar żewġ insla tar-rettili, l-arkosawromorfi (il-kukkudrilli, l-għasafar u l-annimali relatati) u l-lepidosawromorfi (il-gremxul u l-annimali relatati), varjaw minn xulxin matul il-perjodu Permjan.<ref>Ezcurra, M.D.; Scheyer, T.M.; Butler, R.J. (2014). "The origin and early evolution of Sauria: Reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence". ''PLOS ONE''. '''9''' (2) e89165. Bibcode:2014PLoSO...989165E. doi:10.1371/journal.pone.0089165. PMC 3937355. <nowiki>PMID 24586565</nowiki>.</ref> Minbarra r-rettili ħajjin, hemm diversità kbira ta' gruppi li issa huma estinti, f'xi każijiet minħabba avvenimenti ta' estinzjoni tal-massa. B'mod partikolari, l-avveniment tal-estinzjoni fil-perjodu Kretaċju–Paleoġen qered għalkollox il-pterosawri, il-plesjosawri u d-[[Dinosawru|dinosawri]] kollha li ma kinux tjur, flimkien ma' bosta speċijiet ta' kukkudrilloformi u ''Squamata'' (eż. możasawri). Ir-rettili moderni li mhumiex tjur huma mifruxa mal-[[Kontinent|kontinenti]] kollha għajr l-[[Antartika]]. Ir-rettili eżistenti jvarjaw bħala daqs mill-wiżgħa nana ċkejkna ta' Jaragua (''Sphaerodactylus ariasae''), li tikber biss sa 17-il millimetru (0.7 pulzieri); sal-kukkudrill tal-baħar (''Crocodylus porosus''), li jista' jaqbeż tul ta' 6 metri (19.7 pied) u jiżen iktar minn 1,000 kilogramma (2,200 libbra). Bħala tetrapodi, ir-rettili ġeneralment ikollhom erba' saqajn, jew fil-każ tas-sriep u l-gremxul bla saqajn, ikunu dixxendenti minn antenati b'erba' saqajn iżda jkunu tilfu saqajhom matul l-[[evoluzzjoni]]. Għad-differenza tal-anfibji anamnijotiċi, ir-rettili ma jiddependux fuq il-korpi tal-ilma għar-riproduzzjoni u ma jkollhom l-ebda stadju ta' larvi akkwatiċi. Il-biċċa l-kbira tar-rettili huma ovipari b'bajd bil-qoxra, għalkemm diversi speċijiet ta' ''Squamata'' huma vivipari, bħal uħud mir-rettili monofiletiċi estinti tal-baħar.<ref>Sander, P. Martin (2012). "Reproduction in early amniotes". ''Science''. '''337''' (6096): 806–808. Bibcode:2012Sci...337..806S. doi:10.1126/science.1224301. <nowiki>PMID 22904001</nowiki>. S2CID 7041966.</ref> Bħala amnijoti, il-bajd tar-rettili jkollu membrana ekstraembrijonika li żżomm l-ilma u li tiffaċilita l-iskambju bijokimiku mal-ambjent estern, u b'hekk ir-rettili jkunu jistgħu jirriproduċu fuq l-art niexfa, saħansitra f'ħabitats aridi u estremi. L-ispeċijiet vivipari jkollhom il-bajd li jiżviluppa u li jfaqqas fi ħdan il-ġisem tal-omm, normalment b'inkubazzjoni interna, għalkemm xi speċijiet jistgħu jitimgħu l-bajd bħala feti permezz ta' diversi forom ta' plaċenti analogi, u wħud jipprovdu l-indukrar parentali inizjali għall-frieħ tagħhom. == Klassifikazzjoni == === Tassonomija klassika u riċerka === [[Stampa:Reptile003d (group).jpg|daqsminuri|Ir-rettili minn ''Nouveau Larousse Illustré'', 1897–1904, ta' min jinnota l-inklużjoni tal-anfibji (taħt il-''Crocodilia'').]] Fis-seklu 13, il-kategorija tar-''rettili'' ġiet rikonoxxuta fl-[[Ewropa]] bħala waħda li tikkonsisti minn taħlita ta' ħlejqiet li jbidu l-bajd, fosthom "is-sriep, diversi mostri fantastiċi, gremxul, diversi anfibji, u dud", kif irreġistrat minn Beauvais fil-''Mera tan-Natura'' tiegħu. Fis-seklu 18, ir-rettili mill-bidu nett tal-klassifikazzjoni, ġew raggruppati mal-anfibji. [[Carl Linnaeus]], li kien jaħdem fl-[[Żvezja|Iżvezja]] li ma tantx kellha wisq speċijiet, u fejn il-lifgħa u s-serp tal-ħaxix spiss jinstabu jikkaċċjaw fl-ilma, inkluda r-rettili u l-anfibji kollha fil-klassi "III – ''Amphibia''" fis-''Systema Naturæ'' tiegħu. It-[[Terminoloġija|termini]] "rettilu" u "anfibju" fil-biċċa l-kbira kienu interkambjabbli, għalkemm "rettilu" (mil-[[Lingwa Latina|Latin]] ''repere'', "tkaxkar") kien ippreferut mill-[[Franza|Franċiżi]]. [[J.N. Laurenti]] kien l-ewwel wieħed li uża formalment it-terminu ''Reptilia'' għal għażla wiesgħa ta' rettili u ta' anfibji bażikament kif kien għamel Linnaeus. Illum il-ġurnata, iż-żewġ gruppi għadhom trattati bl-istess intestatura unika, jiġifieri l-erpetoloġija. Ma kienx qabel il-bidu tas-seklu 19 li kien ċar li r-rettili u l-anfibji fil-fatt huma annimali pjuttost differenti, u [[P.A. Latreille]] ħoloq il-klassi ''Batracia'' (1825) għal dawn tal-aħħar, u qasam it-tetrapodi fl-erba' klassijiet ta' familji ta' rettili, anfibji, għasafar u mammiferi. L-anatomista [[Renju Unit|Brittaniku]] [[T.H. Huxley]] wassal biex id-definizzjoni ta' Latreille ssir popolari, u flimkien ma' [[Richard Owen]], wessa' r-''Reptilia'' biex jinkludu d-diversi fossili ta' "mostri antedilluvjani", fosthom id-dinosawri u d-''Dicynodon'', li huwa sinapsidu qisu mammiferu li huwa għen biex jiġi deskritt. Din ma kinitx l-unika skema ta' klassifikazzjoni possibbli: fil-lekċers ta' Hunter mogħtija fil-Kulleġġ Irjali tal-[[Kirurgu|Kirurgi]] fl-1863, Huxley ġabar il-vertebrati mal-mammiferi, mas-sawrojdi u mal-iktjojdi (dawn tal-aħħar jinkludu l-ħut u l-anfibji). Sussegwentement huwa ppropona l-ismijiet tas-sawropsidi u tal-iktjopsidi għal dawn iż-żewġ gruppi tal-aħħar. Fl-1866, Haeckel wera li l-vertebrati setgħu jinqasmu abbażi tal-istrateġiji riproduttivi tagħhom, u li r-rettili, l-għasafar u l-mammiferi kienu magħqudin mill-bajd amnijotiku. It-termini ''sawropsidi'' ("uċuħ tal-gremxul") u ''teropsidi'' ("uċuħ tal-bestji") reġgħu ntużaw fl-1916 minn [[E.S. Goodrich]] biex jiddistingwi bejn il-gremxul, l-għasafar u l-qrabat tagħhom minn naħa waħda (sawropsidi) u l-mammiferi u l-qrabat estinti tagħhom (teropsidi) fuq in-naħa l-oħra. Goodrich appoġġa din id-diviżjoni skont in-natura tal-[[Qalb|qlub]] u tal-istrutturi taċ-ċirkolazzjoni tad-[[demm]] f'kull grupp, u karatteristiċi oħra, bħall-istruttura tal-parti ta' quddiem tal-[[moħħ]]. Skont Goodrich, iż-żewġ insla evolvew minn grupp uniku bikri, il-protosawri ("l-ewwel gremxul"), fejn huwa inkluda xi annimali li llum il-ġurnata jitqiesu bħala anfibji qishom rettili, kif ukoll rettili bikrin. [[Stampa:MosasaurDiscovery.jpg|daqsminuri|Inċiżjoni tas-seklu 18 ta' "mostru antedilluvjan", il-możasawru, skopert f'barriera tal-[[ġebla tal-ġir]] f'[[Maastricht]] fl-1770.]] Fl-1956, [[D.M.S. Watson]] osserva li l-ewwel żewġ gruppi nfirdu fi stadju bikri ħafna fl-istorja tar-rettili, għaldaqstant huwa qasam il-protosawri ta' Goodrich bejniethom. Huwa ta interpretazzjoni mill-ġdid tas-sawropsidi u tat-teropsidi sabiex jeskludi l-għasafar u l-mammiferi, rispettivament. B'hekk is-sawropsidi tiegħu kienu jinkludu l-''Procolophonia'', l-''Eosuchia'', il-''Millerosauria'', il-''Chelonia'' (fkieren), l-''iSquamata'' (gremxul u sriep), ir-''Rhynchocephalia'', il-''Crocodilia'', it-"tecodonti" (l-''Archosauria'' bażiċi parafiletiċi), id-dinosawri li ma kinux tjur, il-pterosawri, l-iktijosawri u s-sawropteriġjani. Fl-aħħar tas-seklu 19 ġew offruti għadd ta' definizzjonijiet tar-''Reptilia''. Il-karatteristiċi [[Bijoloġija|bijoloġiċi]] elenkati minn Lydekker fl-1896, pereżempju, jinkludu kondil oċċipitali uniku, ġog tax-xedaq iffurmat mill-għadam tal-kwadrat u artikolari, u ċerti karatteristiċi tal-vertebri. L-annimali li spikkaw permezz ta' dawn il-formulazzjonijiet, l-amnijoti għajr il-mammiferi u l-għasafar, għadhom jitqiesu bħala r-rettili llum il-ġurnata. Id-diviżjoni bejn is-sinapsidi u s-sawropsidi ssupplimentat approċċ ieħor, wieħed li jaqsam ir-rettili f'erba' subklassijiet abbażi tal-għadd u tal-pożizzjoni ta' fetħiet fil-ġnub tal-kranju wara l-għajnejn. Din il-klassifikazzjoni nbdiet minn [[Henry Fairfield Osborn]] u ġiet elaborata u saret popolari permezz tal-''Paleontoloġija tal-Vertebrati'' ta' Romer. Dawn l-erba' subklassijiet kienu: * l-anapsidi – l-ebda fetħa fil-ġnub tal-kranju – kotilosawri u l-''chelonia'' (fkieren u qrabathom); * is-sinapsidi – fetħa baxxa waħda fil-ġnub tal-kranju – pelikosawri u terapsidi (ir-"rettili qishom mammiferi"); * l-ewriapsidi – fetħa għolja waħda fil-ġnub tal-kranju (fuq iż-żona postorbitali u skwamożali) – protorosawri (rettili żgħar u bikrin qishom gremxul) u s-sawropteriġjani u l-iktijosawri tal-baħar, dawn tal-aħħar imsejħa parapsidi fix-xogħol ta' Osborn; * id-diapsidi – żewġ fetħiet fil-ġnub tal-kranju – il-biċċa l-kbira tar-rettili, fosthom il-gremxul, is-sriep, il-kukkudrilli, id-dinosawri u l-pterosawri. Il-kompożizzjoni tal-ewriapsidi ma kinitx ċerta. Xi kultant, l-iktijosawri tqiesu donnhom żdiedu b'mod indipendenti mill-ewriapsidi l-oħra, u ngħataw l-isem iktar antik ta' parapsidi. Iktar 'il quddiem il-parapsidi ġew skartati fil-biċċa l-kbira bħala grupp (l-iktijosawri ġew ikklassifikati bħala ''incertae sedis'' jew mal-ewriapsidi). Madankollu, erba' subklassijiet (jew tlieta jekk l-ewriapsidi jitwaħħdu mad-diapsidi) baqgħu bejn wieħed u ieħor universali għax-xogħol mhux speċjalist matul is-seklu 20. Din fil-biċċa l-kbira ġiet abbandunata mir-riċerkaturi reċenti. B'mod partikolari, instab li l-kundizzjoni tal-anapsidi tant tokkorri b'mod varjabbli fost il-gruppi mhux relatati li issa ma titqiesx bħala distinzjoni utli. === Filoġenetika u definizzjoni moderna === [[Stampa:Varanodon1DB.jpg|daqsminuri|Il-klassifikazzjonijiet filoġenetiċi jiġbru flimkien lir-"rettili qishom mammiferi", bħal dan il-''varanodon'', flimkien ma' sinapsidi oħra, mhux ma' rettili eżistenti.]] Sal-bidu tas-seklu 21, il-paleontologi tal-vertebrati bdew jadottaw tassonomija filoġenetika, fejn il-gruppi kollha jiġu defini b'tali mod li jkunu monofiletiċi; jiġifieri, gruppi li jinkludu d-dixxendenti kollha ta' antenat partikolari. Storikament ir-rettili ġew definiti bħala parafiletiċi, peress li jeskludu l-għasafar u l-mammiferi. Dawn evolvew rispettivament mid-dinosawri u minn terapsidi bikrin, li t-tnejn li huma tradizzjonalment kienu jissejħu "rettili". L-għasafar huma relatati iktar mill-qrib mal-''Crocodilia'' milli dawn tal-aħħar huma mal-bqija tar-rettili eżistenti. [[Colin Tudge]] kiteb:<blockquote>Il-mammiferi huma grupp monofiletiku, u għaldaqstant dawk li jippreferu tali klassifikazzjoni lesti li jirrikonoxxu t-[[takson]] tradizzjonali ''Mammalia''; u l-għasafar ukoll huma grupp monofiletiku, li universalment jitqies li jappartjeni għat-takson formali ''Aves''. Il-''Mammalia'' u l-''Aves'' fil-fatt huma sottogruppi monofiletiċi fi ħdan grupp monofiletiku kbir tal-''Amniota''. Iżda l-klassi tradizzjonali tar-''Reptilia'' mhijiex grupp monofiletiku. Hija biss sezzjoni mill-grupp monofiletiku tal-''Amniota'': is-sezzjoni li jifdal wara li jitneħħew il-''Mammalia'' u l-''Aves''. Ma tistax tiġi definita kif suppost skont is-sinapomorfji. Minflok, tiġi definita skont taħlita tal-karatteristiċi li għandha u tal-karatteristiċi li ma għandhiex: ir-rettili huma l-amnijoti li ma jkollhomx pil jew rix. L-iktar l-iktar, dawk li jippreferu tali klassifikazzjoni jissuġġerixxu li wieħed jista' jgħid li r-''Reptilia'' tradizzjonali huma amnijoti "li ma jkunux tjur u li ma jkunux mammiferi".</blockquote>Minkejja l-proposti bikrin biex ir-''Reptilia'' parafiletiċi jiġu sostitwiti bis-sawropsidi monofiletiċi, li jinkludu l-għasafar, dak it-terminu qatt ma ġie adottat b'mod mifrux, jew meta beda jiġi adottat, ma ġiex applikat b'mod konsistenti. Meta ntuża t-terminu sawropsidi, spiss kien jinkludi l-istess kontenut jew saħansitra kellu l-istess definizzjoni bħar-''Reptilia''. Fl-1988, [[Jacques Gauthier]] ippropona definizzjonali tar-''Reptilia'' bħala grupp monofiletiku ewlieni li jinkludi l-fkieren, il-gremxul u s-sriep, il-kukkudrilli u l-għasafar, flimkien mal-antenati komuni tagħhom u d-dixxendenti kollha tagħhom. Filwaqt li d-definizzjoni ta' Gauthier kienet qrib għall-konsensus modern, minkejja dan bdiet titqies bħala mhux adegwata minħabba r-relazzjoni effettiva tal-fkieren ma' rettili oħra dak iż-żmien ma kinitx mifhuma sew. Minn dak iż-żmien saru reviżjonijiet kbar li inkludew l-assenjar mill-ġdid tas-sinapsidi bħala mhux rettili, u l-klassifikazzjoni tal-fkieren bħala diapsidi. Id-definizzjoni ta' Gauthier fl-1994 u ta' Laurin u Reisz fl-1995 tas-sawropsidi wasslet għal definizzjoni tal-ambitu tal-grupp bħala wieħed distint u usa' minn dak tar-''Reptilia'', u jħaddan il-''Mesosauridae'' kif ukoll ir-''Reptilia'' ''sensu stricto''. Varjetà sħiħa ta' definizzjonijiet oħra ġew proposti minn xjenzati oħra fis-snin ta' wara d-dokument ta' Gauthier. L-ewwel waħda fost tali definizzjonijiet, li ppruvat taderixxi mal-istandards tal-Kodiċi Filoġenetiku ġiet ippubblikata minn Modesto u Anderson fl-2004. Modesto u Anderson irrieżaminaw il-bosta definizzjonijiet preċedenti u pproponew definizzjoni modifikata, u kellhom il-ħsieb li jżommu l-iżjed kontenut tradizzjonali tal-grupp filwaqt li jħalluh stabbli u monofiletiku. Huma ddefinew ir-''Reptilia'' bħala l-amnijoti kollha li huma eqreb għal-''Lacerta agilis'' u għall-''Crocodylus niloticus'' mill-''[[Homo sapiens]]''. Din id-definizzjoni hija ekwivalenti għall-iktar definizzjoni komuni tas-sawropsidi, li Modesto u Anderson sostnew li kienu sinonimu tar-''Reptilia'', peress li dan it-terminu tal-aħħar huwa magħruf iktar u jintuża iktar spiss. Madankollu, għad-differenza tal-biċċa l-kbira tad-definizzjonijiet preċedenti tar-''Reptilia'', id-definizzjoni ta' Modesto u Anderson tinkludi l-għasafar, peress li huma fi ħdan il-grupp monofiletiku li jinkludi kemm il-gremxul kif ukoll il-kukkudrilli. === Tassonomija === Klassifikazzjoni ġenerali tar-rettili estinti u ħajjin, li tiffoka fuq il-gruppi ewlenin: * '''''Reptilia'''/'''Sauropsida''''' ** ''Araeoscelidia?'' ** <abbr>†</abbr>'''''Parareptilia''''' (x'aktarx parafiletiċi) *** '''''Diapsida'''/'''Neodiapsida''''' **** <abbr>†</abbr>''Drepanosauromorpha'' (kollokazzjoni inċerta) **** <abbr>†</abbr>''Younginiformes'' (x'aktarx parafiletiċi) **** <abbr>†</abbr>Ichthyosauromorpha (kollokazzjoni inċerta) **** <abbr>†</abbr>''Thalattosauria'' (kollokazzjoni inċerta) **** <abbr>†</abbr>''Sauropterygia'' (kollokazzjoni inċerta) **** <abbr>†</abbr>''Choristodera'' (kollokazzjoni inċerta) **** '''''Sauria''''' ***** '''''Lepidosauromorpha''''' ****** ''Lepidosauria'' ******* ''Rhynchocephalia'' (tuatara) ******* ''Squamata'' (gremxul u sriep) ***** '''''Pantestudines''''' (fkieren u qrabat, kollokazzjoni inċerta) ***** '''''Archosauromorpha''''' ****** <abbr>†</abbr>''Protorosauria'' (parafiletiċi) ****** <abbr>†</abbr>''Rhynchosauria'' ****** <abbr>†</abbr>''Allokotosauria'' ****** ''Archosauriformes'' ******* <abbr>†</abbr>''Phytosauria'' ******* '''''Archosauria''''' ******** ''Pseudosuchia'' ********* ''Crocodilia'' (kukkudrilli u qrabat) ******** ''Avemetatarsalia/Ornithodira'' ********* <abbr>†</abbr>''Pterosauria'' ********* ''Dinosauria'' ********** <abbr>†</abbr>''Ornithischia'' ********** ''Saurischia'' (inkluż l-għasafar ('''''Aves''''')) === Filoġenija === L-"arblu tar-razza" tar-rettili jsegwi verżjoni ssimplifikata tar-relazzjonijiet li nstabu minn M.S. Lee fl-2013. L-istudji ġenetiċi kollha appoġġaw l-ipoteżi li l-fkieren huma diapsidi; uħud poġġew il-fkieren fi ħdan l-''Archosauromorpha'', għalkemm uħud minflok poġġew il-fkieren bħala ''Lepidosauromorpha''. === Il-pożizzjoni tal-fkieren === Il-kollokazzjoni tal-fkieren storikament kienet varjabbli ferm. Klassikament, il-fkieren ġew meqjusa bħala relatati mar-rettili anapsidi primittivi. Fl-analiżi komparattiva tagħhom tal-kronoloġija tal-organoġenesi, Werneburg u Sánchez-Villagra (2009) sabu appoġġ għall-ipoteżi li l-fkieren jagħmlu parti minn grupp monofiletiku separat fi ħdan is-sawropsidi, barra mill-grupp monofiletiku sawrjan. Normalment ix-xogħol molekolari wassal għall-kollokazzjoni tal-fkieren fi ħdan id-diapsidi. Sal-2013 ġew sekwenzjati tliet ġenomi tal-fkieren. Ir-riżultati jikkollokaw il-fkieren bħala grupp monofiletiku relatat mal-arċosawri, li huma l-grupp li jinkludi l-''Crocodilia'', id-dinosawri li mhumiex tjur u l-għasafar. == Storja evoluzzjonarja == === Oriġini tar-rettili === L-oriġini tar-rettili tmur lura madwar 310–320 miljun sena ilu, fl-artijiet bassasa bl-istim tal-perjodu Karboniferu aħħari, meta l-ewwel rettili evolvew minn rettilomorfi avvanzati. L-iktar annimal tal-qedem magħruf li jaf kien amnijota huwa l-''Casineria'' (għalkemm jaf kien temnospondil). Sensiela ta' impronti tas-saqajn mis-saff tal-fossili ta' Nova Scotia li jmorru lura għal 315-il miljun sena fihom impronti tipiċi tas-swaba' tar-rettili u impronti tal-qxur tal-ġilda. Dawn l-impronti tas-saqajn issa ġew attribwiti lill-''Hylonomus'', li storikament jitqies bħala l-iktar rettilu tal-qedem magħruf, iżda l-kollokazzjoni tiegħu fil-grupp dan l-aħħar ġiet dubitata. Dan kien annimal żgħir qisu gremxula, twil madwar 20 sa 30 ċentimetru (7.9 pulzieri sa 11.8 pulzier), b'bosta snien ippuntati li jindikaw dieta [[Insettivoru|insettivora]]. Eżempji oħra jinkludu l-''Westlothiana'' (li attwalment jitqies bħala rettilomorfu iktar milli amnijota reali) u l-''Paleothyris'', it-tnejn li huma ta' daqs simili u x'aktarx b'imġiba simili. Madankollu, il-mikrosawri xi kultant tqiesu bħala rettili reali, għaldaqstant jaf hija possibbli oriġini iktar bikrija. Fost ir-rettili reali mhux ambigwi mill-perjodu Karboniferu hemm l-''Erpetonyx'' u l-''Carbonodraco,'' it-tnejn li huma mill-[[L-Amerika ta' Fuq|Amerka ta' Fuq]]. === Żieda tar-rettili === L-iżjed amnijoti bikrin, fosthom l-anapsidi primittivi (jiġifieri l-amnijoti li huma eqreb għar-rettili moderni milli għall-mammiferi), fil-biċċa l-kbira ħadulhom posthom it-tetrapodi primittivi l-kbar bħall-''Cochleosaurus'', u baqgħu parti żgħira tal-fawna sal-Kollass Karboniferu tal-Foresti Pluvjali. Dan il-kollass ħesrem affettwa diversi gruppi kbar. It-tetrapodi primittivi ġew devastati partikolarment, filwaqt li r-rettili primittivi marru aħjar, peress li kienu adattati [[Ekoloġija|ekoloġikament]] għall-kundizzjonijiet iktar nexfin li ġew wara. It-tetrapodi primittivi, bħall-anfibji moderni, ikollhom jerġgħu lura fl-ilma biex ibidu l-bajd; f'kuntrast ma' dan, l-amnijoti, bħar-rettili moderni – li l-bajd tagħhom fih qoxra li permezz tagħha jista' jinbied fuq l-art – kienu adattati aħjar għall-kundizzjonijiet il-ġodda. L-amnijoti kisbu niċeċ ġodda b'rata iktar mgħaġġla minn qabel il-kollass u ferm iktar malajr mit-tetrapodi primittivi. Kisbu strateġiji ġodda tal-alimentazzjoni, inkluż strateġiji [[Erbivoru|erbivori]] u [[Karnivoru|karnivori]], mentri qabel kienu insettivori u pixxivori biss. Minn dak iż-żmien 'il quddiem, ir-rettili ddominaw il-komunitajiet u kellhom diversità akbar mit-tetrapodi primittivi, għaldaqstant dan witta t-triq għall-perjodu Mesożojku (magħruf bħala l-Era tar-Rettili). Eżami tal-2021 tad-diversità tar-rettili fil-perjodu Karboniferu u fil-perjodu Permjan jissuġġerixxi livell ferm ogħla ta' diversità milli kien maħsub qabel, li huwa komparabbli jew saħansitra li jaqbeż dak tas-sinapsidi. Għalhekk ġiet proposta l-"Ewwel Era tar-Rettili". === Anapsidi, sinapsidi, diapsidi u sawropsidi === Tradizzjonalment kien maħsub li l-ewwel rettili kellhom kranju ta' anapsidi li wirtuh mill-antenati tagħhom. Dan it-tip ta' kranju kien fih għamla b'saħħitha b'toqob għall-imnieħer, għall-għajnejn u għall-glandola pineali. L-iskoperti ta' fetħiet qishom tas-sinapsidi fil-kranju ta' diversi membri tal-''Parareptilia'' (il-grupp li fih il-biċċa l-kbira tal-amnijoti tradizzjonalment magħrufa bħala "anapsidi"), inkluż il-lantanosukojdi, il-millerettidi, il-bolosawridi, xi nikteroleteridi, xi prokolofonojdi u mqar xi mesosawri, wasslu biex l-affarijiet ikunu iktar ambigwi u attwalment ma hemmx ċertezza dwar jekk l-amnijoti anċestrali kellhomx kranju qisu tal-anapsidi jew kranju qisu tas-sinapsidi. Tradizzjonalment dawn l-annimali jissejħu "anapsidi" u jiffurmaw grupp bażiku parafiletiku li minnu evolvew gruppi oħra. Ftit wara li tfaċċaw l-ewwel amnijoti, in-nisel tas-sinapsidi nqasam għalih waħdu; dan il-grupp kien karatterizzat minn fetħa fil-kranju wara kull għajn biex b'hekk il-muskolu tax-xedaq kellu biżżejed spazju biex jiċċaqlaq. Dawn huma l-"amnijoti qishom mammiferi" jew mammiferi primittivi, li iktar 'il quddiem wasslu għall-mammiferi reali. Ftit wara, grupp ieħor evolva karatteristika simili, din id-darba b'fetħa doppja wara kull għajn, u b'hekk issejjaħ ''Diapsida'' ("żewġ ħnejjiet"). Il-funzjoni tat-toqob f'dawn il-gruppi kienet li jitħaffef il-kranju u jkun hemm biżżejjed spazju biex il-muskoli tax-xedaq jiċċaqilqu, u b'hekk l-annimal seta' jkollu gidma qawwija. Storikament, filwaqt li l-grupp tar-rettili qishom gremxul tal-perjodu Karboniferu aħħari u tal-perjodu Permjan bikri tal-''Araeoscelidia'', li (ġeneralment) huma diapsidi morfoloġikament, ġew meqjusa bħala l-iżjed rappreżentanti bikrin tal-grupp monofiletiku tad-diapsidi, l-istudji filoġenetiċi mis-snin 20 tas-seklu 20 wasslu għal dubji serji rigward ir-relazzjoni tagħhom ma' diapsidi oħra (''Neodiapsida''), u ġew meqjusa bħala fergħa diverġenti bikrija ħafna tar-''Reptilia'' jew saħansitra barra mir-''Reptilia'' għalkollox. Tradizzjonalment kien maħsub li l-fkieren kienu pararettili ħajjin, abbażi tal-istruttura tal-kranju tagħhom bħala anapsidi, u dan ġie meqjus bħala karatteristika primittiva. Ir-raġunament li wassal għal din il-klassifikazzjoni ġie kkontestat, u wħud argumentaw li l-fkieren huma diapsidi li evolvew kranji tal-anapsidi, u b'hekk tejbu d-difiżi tagħhom. Studji filoġenetiċi morfoloġiċi li saru wara b'dan il-ħsieb ikkollokaw il-fkieren sew fi ħdan id-diapsidi. L-istudji molekolari kollha appoġġaw il-kollokazzjoni tal-fkieren fi ħdan id-diapsidi, l-iktar bħala grupp relatat mal-arċosawri eżistenti. === Rettili Permjani === Lejn l-aħħar tal-perjodu Karboniferu, l-amnijoti saru t-tetrapodi dominanti fost il-fawna. Filwaqt li xorta waħda kienu jeżistu rettilomorfi terrestri primittivi, l-amnijoti sinapsidi evolvew fl-ewwel megafawna (annimali ġganteski) tassew terrestri fil-forma ta' pelikosawri, bħall-edafosawru u d-dimetrodon karnivoru. F'nofs il-perjodu Permjan, il-klima saret iktar niexfa, u dan irriżulta f'bidla fil-fawna: il-pelikosawri ġew sostitwiti mit-terapsidi. Bosta gruppi ta' rettili primittivi baqgħu jiffjorixxu matul il-perjodu Permjan. Il-parejasawri erbivori kienu l-ewwel nisel tar-rettili li laħqu daqs kbir, u l-ikbar rappreżentanti tal-grupp kellhom massa tal-ġisem li x'aktarx li qabżet l-1,000 kilogramma (2,200 libbra). Wieħed mill-iktar rettili primittivi bikrin magħrufa huwa l-mesosawru, [[Ġeneru (tassonomija)|ġeneru]] mill-Permjan Bikri tan-Nofsinhar tal-[[Afrika]] u tal-[[L-Amerika t'Isfel|Amerka t'Isfel]] li kien reġa' lura fl-ilma u kien kiseb saqajn bis-swaba' magħqudin, u kien jiekol il-krustaċji fl-ambjenti tal-baħar jew tal-laguni. L-iżjed diapsidi reali bikrin (neodiapsidi), bħall-''Youngina'', tfaċċaw matul il-perjodu Permjan Nofsani-Aħħari. Il-''Weigeltisauridae'', grupp ta' diapsidi mill-Permjan Aħħari, huma l-eqdem tetrapodi magħrufa li kienu jtiru permezz ta' għadmiet innovattivi qishom vireg li kienu jiġu estiżi minn ġisimhom u kienu jiffurmaw ġwienaħ għall-igglajdjar bejn is-siġar. L-antenati tar-rettili moderni (li jagħmlu parti mill-grupp monofiletiku tas-''Sauria'') ma baqgħux jagħmlu parti mill-istess grupp sal-Permjan Aħħari, kif joħroġ fid-dieher minn speċijiet bħall-protosawru qisu varan magħruf mill-Permjan Aħħari tal-[[Ewropa]], li huwa ċar li huwa arċosawromorfu, relatat iktar mill-qrib mal-arċosawri (''Crocodilia'' u għasafar) milli mal-gremxul, mas-sriep jew mal-fkieren. === Rettili Mesożojċi === Fl-aħħar tal-perjodu Permjan seħħet l-ikbar estinzjoni tal-massa magħrufa, avveniment li ddewwem b'sensiela ta' żewġ mewġiet distinti jew iktar ta' estinzjoni. Il-biċċa l-kbira tal-pararettili bikrin u tal-megafawna sinapsidi għebu, u ġew sostitwiti bir-rettili reali, b'mod partikolari l-arċisawromorfi. Dawn kienu kkaratterizzati minn riġlejn ta' wara tawwalin u poża wieqfa, filwaqt li l-forom bikrin kienu jidhru qishom kukkudrilli b'riġlejn twal. L-arċosawri saru l-grupp dominanti matul il-perjodu Triassiku, għalkemm għaddew 30 miljun sena qabel ma d-diversità tagħhom ma saret tant kbira daqs l-annimali li għexu fil-perjodu Permjan. L-arċosawri żviluppaw fid-dinosawri u fil-pterosawri magħrufa sew, kif ukoll fl-antenati tal-''Crocodilia''. Ladarba r-rettili, l-ewwel rawisukjani u mbagħad id-dinosawri, iddominaw il-perjodu Mesożojku, l-intervall huwa magħruf b'mod popolari bħala l-"Era tar-Rettili". Id-dinosawri żviluppaw ukoll f'forom iżgħar, inkluż it-teropodi iżgħar bir-rix. Fil-perjodu Kretaċju, dawn wasslu għall-ewwel għasafar reali. L-eqreb grupp tal-arċosawromorfi huwa tal-lepidosawromorfi, li jinkludi l-gremxul u t-tuatara, kif ukoll il-qrabat fossili tagħhom. Il-lepidosawromorfi kienu jinkludu mill-inqas grupp ewlieni tar-rettili tal-baħar tal-perjodu Mesożojku: il-możasawri, li għexu matul il-perjodu Kretaċju. Il-kollokazzjoni filoġenetika ta' gruppi prinċipali oħra ta' rettili tal-baħar fossili – l-iktjopteriġjani (inkluż l-iktjosawri) u s-sawropteriġjani, li evolvew fil-perjodu Triassiku bikri – hija iktar kontroversjali. Awturi differenti rabtu dawn il-gruppi mal-lepidosawromorfi jew mal-arċosawromorfi, u l- iktjopteriġjani ġew ippreżentati wkoll bħala diapsidi li ma kinux jagħmlu parti mal-inqas grupp monofiletiku inklużiv, li fih il-lepidosawromorfi u l-arċosawromorfi. === Rettili Ċenożojċi === 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 extinction event). Of the large marine reptiles, only sea turtles were left; and of the non-marine large reptiles, only the semi-aquatic crocodilians and broadly similar choristoderes survived the extinction, with last members of the latter, the lizard-like ''Lazarussuchus'', becoming extinct in the Miocene. 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. However, reptiles were still important components of the megafauna, particularly in the form of large and giant tortoises. After the extinction of most archosaur and marine reptile lines by the end of the Cretaceous, reptile diversification continued throughout the Cenozoic. Squamates took a massive hit during the K–Pg event, only recovering ten million years after it, but they underwent a great radiation event once they recovered, and today squamates make up the majority of living reptiles (> 95%). 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 living species (excluding domesticated species). {| class="wikitable" |+Diversità ta' speċijiet ta' rettili ħajjin (2013) !Grupp ta' rettili !Speċijiet deskritti !Persentaġġ tal-ispeċijiet ta' rettili |- |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 % |} == Morfoloġija u fiżjoloġija == === Ċirkolazzjoni === All lepidosaurs and turtles have a three-chambered heart consisting of two atria, one variably partitioned ventricle, and two aortas that lead to the systemic circulation. The degree of mixing of oxygenated and deoxygenated blood in the three-chambered heart varies depending on the species and physiological state. Under different conditions, deoxygenated blood can be shunted back to the body or oxygenated blood can be shunted back to the lungs. This variation in blood flow has been hypothesized to allow more effective thermoregulation and longer diving times for aquatic species, but has not been shown to be a fitness advantage. For example, iguana hearts, like the majority of the squamate hearts, are composed of three chambers–two atria and one ventricle–and cardiac involuntary muscles. The main structures of the heart are the sinus venosus, the pacemaker, the left atrium, the right atrium, the atrioventricular valve, the cavum venosum, cavum arteriosum, the cavum pulmonale, the muscular ridge, the ventricular ridge, pulmonary veins, and paired aortic arches. Some squamate species (e.g., pythons and monitor lizards) have three-chambered hearts that become functionally four-chambered hearts during contraction. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts. Crocodilians have an anatomically four-chambered heart, similar to birds, but also have two systemic aortas and are therefore capable of bypassing their pulmonary circulation. In turtles, the ventricle is not perfectly divided, so a mix of aerated and nonaerated blood can occur. === Metaboliżmu === Modern non-avian reptiles exhibit some form of cold-bloodedness (i.e. some mix of poikilothermy, ectothermy, and bradymetabolism) so that they have limited physiological means of keeping the body temperature constant and often rely on external sources of heat. Due to a less stable core temperature than birds and mammals, reptilian biochemistry requires enzymes capable of maintaining efficiency over a greater range of temperatures than in the case for warm-blooded animals. The optimum body temperature range varies with species, but is typically below that of warm-blooded animals; for many lizards, it falls in the 24–35 °C (75–95 °F) range, while extreme heat-adapted species, like the American desert iguana ''Dipsosaurus dorsalis'', can have optimal physiological temperatures in the mammalian range, between 35 and 40 °C (95 and 104 °F). While the optimum temperature is often encountered when the animal is active, the low basal metabolism makes body temperature drop rapidly when the animal is inactive. As in all animals, reptilian muscle action produces heat. In large reptiles, like leatherback turtles, the low surface-to-volume ratio allows this metabolically produced heat to keep the animals warmer than their environment even though they do not have a warm-blooded metabolism. This form of homeothermy is called gigantothermy; it has been suggested as having been common in large dinosaurs and other extinct large-bodied reptiles. The benefit of a low resting metabolism is that it requires far less fuel to sustain bodily functions. By using temperature variations in their surroundings, or by remaining cold when they do not need to move, reptiles can save considerable amounts of energy compared to endothermic animals of the same size. A crocodile needs from a tenth to a fifth of the food necessary for a lion of the same weight and can live half a year without eating. Lower food requirements and adaptive metabolisms allow reptiles to dominate the animal life in regions where net calorie availability is too low to sustain large-bodied mammals and birds. It is generally assumed that reptiles are unable to produce the sustained high energy output necessary for long distance chases or flying. Higher energetic capacity might have been responsible for the evolution of warm-bloodedness in birds and mammals. However, investigation of correlations between active capacity and thermophysiology show a weak relationship. Most extant reptiles are carnivores with a sit-and-wait feeding strategy; whether reptiles are cold blooded due to their ecology is not clear. Energetic studies on some reptiles have shown active capacities equal to or greater than similar sized warm-blooded animals. === Sistema respiratorja === [[/wiki/File:X-ray_video_of_a_female_American_alligator_(Alligator_mississippiensis)_while_breathing_-_pone.0004497.s009.ogv|lemin|daqsminuri|Filmati ta' fluworoskopija bir-raġġi X ta' alligatur Amerikan femminili li juru l-kontrazzjoni tal-pulmuni waqt it-teħid tan-nifs.]] All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange. Even with these adaptations, breathing is never fully accomplished without lungs. Lung ventilation is accomplished differently in each main reptile group. In squamates, the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing". This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs. Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the "hepatic piston". The airways form a number of double tubular chambers within each lung. On inhalation and exhalation air moves through the airways in the same direction, thus creating a unidirectional airflow through the lungs. A similar system is found in birds, monitor lizards and iguanas. Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains against damage by struggling prey). Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation. ==== Fkieren tal-ilma u fkieren tal-art ==== How turtles breathe has been the subject of much study. To date, only a few species have been studied thoroughly enough to get an idea of how those turtles breathe. The varied results indicate that turtles have found a variety of solutions to this problem. The difficulty is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles, such as the Indian flapshell (''Lissemys punctata''), have a sheet of muscle that envelops the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. By using a series of special muscles (roughly equivalent to a diaphragm), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction). Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements. This is because they use their abdominal muscles to breathe during locomotion. The last species to have been studied is the red-eared slider, which also breathes during locomotion, but takes smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Box turtles have also been observed to breathe while completely sealed up inside their shells. === Produzzjoni tal-ħsejjes === Compared with frogs, birds, and mammals, reptiles are less vocal. Sound production is usually limited to hissing, which is produced merely by forcing air though a partly closed glottis and is not considered to be a true vocalization. The ability to vocalize exists in crocodilians, some lizards and turtles; and typically involves vibrating fold-like structures in the larynx or glottis. Some geckos and turtles possess true vocal cords, which have elastin-rich connective tissue. ==== Smigħ fis-sriep ==== Hearing in humans relies on 3 parts of the ear; the outer ear that directs sound waves into the ear canal, the middle ear that transmits incoming sound waves to the inner ear, and the inner ear that helps in hearing and keeping their balance. Unlike humans and other mammals, snakes do not possess an outer ear, a middle ear, and a tympanum but have an inner ear structure with cochleas directly connected to their jawbone. They are able to feel the vibrations generated from the sound waves in their jaw as they move on the ground. This is done by the use of mechanoreceptors, sensory nerves that run along the body of snakes directing the vibrations along the spinal nerves to the brain. Snakes have a sensitive auditory perception and can tell which direction sound being made is coming from so that they can sense the presence of prey or predator but it is still unclear how sensitive snakes are to sound waves traveling through the air. === Ġilda === Reptilian skin is covered in a horny epidermis, making it watertight and enabling reptiles to live on dry land, in contrast to amphibians. Compared to mammalian skin, that of reptiles is rather thin and lacks the thick dermal layer that produces leather in mammals. Exposed parts of reptiles are protected by scales or scutes, sometimes with a bony base (osteoderms), forming armor. In lepidosaurs, such as lizards and snakes, the whole skin is covered in overlapping epidermal scales. Such scales were once thought to be typical of the class Reptilia as a whole, but are now known to occur only in lepidosaurs. The scales found in turtles and crocodiles are of dermal, rather than epidermal, origin and are properly termed scutes. In turtles, the body is hidden inside a hard shell composed of fused scutes. Lacking a thick dermis, reptilian leather is not as strong as mammalian leather. It is used in leather-wares for decorative purposes for shoes, belts and handbags, particularly crocodile skin. ==== Bdil tal-qxur ==== Reptiles shed their skin through a process called ecdysis which occurs continuously throughout their lifetime. In particular, younger reptiles tend to shed once every five to six weeks while adults shed three to four times a year. Younger reptiles shed more because of their rapid growth rate. Once full size, the frequency of shedding drastically decreases. The process of ecdysis involves forming a new layer of skin under the old one. Proteolytic enzymes and lymphatic fluid is secreted between the old and new layers of skin. Consequently, this lifts the old skin from the new one allowing shedding to occur. Snakes will shed from the head to the tail while lizards shed in a "patchy pattern". Dysecdysis, a common skin disease in snakes and lizards, will occur when ecdysis, or shedding, fails. There are numerous reasons why shedding fails and can be related to inadequate humidity and temperature, nutritional deficiencies, dehydration and traumatic injuries. Nutritional deficiencies decrease proteolytic enzymes while dehydration reduces lymphatic fluids to separate the skin layers. Traumatic injuries on the other hand, form scars that will not allow new scales to form and disrupt the process of ecdysis. === Eskrezzjoni === Excretion is performed mainly by two small kidneys. In diapsids, uric acid is the main nitrogenous waste product; turtles, like mammals, excrete mainly urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure called a loop of Henle, which is present in the nephrons of birds and mammals. Because of this, many reptiles use the colon to aid in the reabsorption of water. Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt glands in some reptiles. In all reptiles, the urinogenital ducts and the rectum both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards, but is lacking in the monitor lizard, the legless lizards. It is absent in the snakes, alligators, and crocodiles. Many turtles and lizards have proportionally very large bladders. Charles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight. Such adaptations are the result of environments such as remote islands and deserts where water is very scarce. Other desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in osmoregulation. Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity. Their bladder is also usually bilobed with a left and right section. The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi. === Diġestjoni === Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest. Digestion is slower than in mammals, reflecting their lower resting metabolism and their inability to divide and masticate their food. Their poikilotherm metabolism has very low energy requirements, allowing large reptiles like crocodiles and large constrictors to live from a single large meal for months, digesting it slowly. While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: in the Paleozoic, the pareiasaurs; and in the Mesozoic several lines of dinosaurs. Today, turtles are the only predominantly herbivorous reptile group, but several lines of agamas and iguanas have evolved to live wholly or partly on plants. Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles (so called gastroliths) to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter. Fossil gastroliths have been found associated with both ornithopods and sauropods, though whether they actually functioned as a gastric mill in the latter is disputed. Salt water crocodiles also use gastroliths as ballast, stabilizing them in the water or helping them to dive. A dual function as both stabilizing ballast and digestion aid has been suggested for gastroliths found in plesiosaurs. === Nervituri === The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well developed with certain exceptions, most notably the snake's lack of external ears (middle and inner ears are present). There are twelve pairs of cranial nerves. Due to their short cochlea, reptiles use electrical tuning to expand their range of audible frequencies. === Vista === Most reptiles are diurnal animals. The vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals. Reptiles usually have excellent vision, allowing them to detect shapes and motions at long distances. They often have poor vision in low-light conditions. Birds, crocodiles and turtles have three types of photoreceptor: rods, single cones and double cones, which gives them sharp color vision and enables them to see ultraviolet wavelengths. The lepidosaurs appear to have lost the duplex retina and only have a single class of receptor that is cone-like or rod-like depending on whether the species is diurnal or nocturnal. In many burrowing species, such as blind snakes, vision is reduced. Many lepidosaurs have a photosensory organ on the top of their heads called the parietal eye, which are also called third eye, pineal eye or pineal gland. This "eye" does not work the same way as a normal eye does as it has only a rudimentary retina and lens and thus, cannot form images. It is, however, sensitive to changes in light and dark and can detect movement. Some snakes have extra sets of visual organs (in the loosest sense of the word) in the form of pits sensitive to infrared radiation (heat). Such heat-sensitive pits are particularly well developed in the pit vipers, but are also found in boas and pythons. These pits allow the snakes to sense the body heat of birds and mammals, enabling pit vipers to hunt rodents in the dark. Most reptiles, as well as birds, possess a nictitating membrane, a translucent third eyelid which is drawn over the eye from the inner corner. In crocodilians, it protects its eyeball surface while allowing a degree of vision underwater. However, many squamates, geckos and snakes in particular, lack eyelids, which are replaced by a transparent scale. This is called the brille, spectacle, or eyecap. The brille is usually not visible, except for when the snake molts, and it protects the eyes from dust and dirt. === Riproduzzjoni === Reptiles generally reproduce sexually, though some are capable of asexual reproduction. All reproductive activity occurs through the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated. Most reptiles have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis, while squamates, including snakes and lizards, possess a pair of hemipenes, only one of which is typically used in each session. Tuatara, however, lack copulatory organs, and so the male and female simply press their cloacas together as the male discharges sperm. Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion (5), chorion (6), and allantois (8) are present during embryonic life. The eggshell (1) protects the crocodile embryo (11) and keeps it from drying out, but it is flexible to allow gas exchange. The chorion (6) aids in gas exchange between the inside and outside of the egg. It allows carbon dioxide to exit the egg and oxygen gas to enter the egg. The albumin (9) further protects the embryo and serves as a reservoir for water and protein. The allantois (8) is a sac that collects the metabolic waste produced by the embryo. The amniotic sac (10) contains amniotic fluid (12) which protects and cushions the embryo. The amnion (5) aids in osmoregulation and serves as a saltwater reservoir. The yolk sac (2) surrounding the yolk (3) contains protein and fat rich nutrients that are absorbed by the embryo via vessels (4) that allow the embryo to grow and metabolize. The air space (7) provides the embryo with oxygen while it is hatching. This ensures that the embryo will not suffocate while it is hatching. There are no larval stages of development. Viviparity and ovoviviparity have evolved in squamates and many extinct clades of reptiles. Among squamates, many species, including all boas and most vipers, use this mode of reproduction. The degree of viviparity varies; some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, and yet others lack any yolk and provide all nutrients via a structure similar to the mammalian placenta. The earliest documented case of viviparity in reptiles is the Early Permian mesosaurs, although some individuals or taxa in that clade may also have been oviparous because a putative isolated egg has also been found. Several groups of Mesozoic marine reptiles also exhibited viviparity, such as mosasaurs, ichthyosaurs, and Sauropterygia, a group that includes pachypleurosaurs and Plesiosauria. Asexual reproduction has been identified in squamates in six families of lizards and one snake. In some species of squamates, a population of females is able to produce a unisexual diploid clone of the mother. This form of asexual reproduction, called parthenogenesis, occurs in several species of gecko, and is particularly widespread in the teiids (especially ''Aspidocelis'') and lacertids (''Lacerta''). In captivity, Komodo dragons (Varanidae) have reproduced by parthenogenesis. Parthenogenetic species are suspected to occur among chameleons, agamids, xantusiids, and typhlopids. Some reptiles exhibit temperature-dependent sex determination (TDSD), in which the incubation temperature determines whether a particular egg hatches as male or female. TDSD is most common in turtles and crocodiles, but also occurs in lizards and tuatara. To date, there has been no confirmation of whether TDSD occurs in snakes. === Lonġevità === Giant tortoises are among the longest-lived vertebrate animals (over 100 years by some estimates) and have been used as a model for studying longevity. DNA analysis of the genomes of Lonesome George, the iconic last member of ''Chelonoidis abingdonii'', and the Aldabra giant tortoise ''Aldabrachelys gigantea'' led to the detection of lineage-specific variants affecting DNA repair genes that might contribute to our understanding of increased lifespan. == Konjizzjoni == Reptiles were traditionally considered less intelligent on average than mammals and birds, but this is increasingly suspected to be the result of poor methodologies in past research and overreliance on brain size as indicators of intelligence rather than a genuine trait of reptiles. The size of their brain relative to their body is much less than that of mammals, the encephalization quotient being about one tenth of that of mammals, though larger reptiles can show more complex brain development. Larger lizards, like the monitors, are known to exhibit complex behavior, including cooperation and cognitive abilities allowing them to optimize their foraging and territoriality over time. Crocodiles have relatively larger brains and show a fairly complex social structure. The Komodo dragon is even known to engage in play, as are turtles, which are also considered to be social creatures, and sometimes switch between monogamy and promiscuity in their sexual behavior.^{[''citation needed'']} One study found that wood turtles were better than white rats at learning to navigate mazes. Another study found that giant tortoises are capable of learning through operant conditioning, visual discrimination and retained learned behaviors with long-term memory. Sea turtles have been regarded as having simple brains, but their flippers are used for a variety of foraging tasks (holding, bracing, corralling) in common with marine mammals. There is evidence that reptiles are sentient and able to feel emotions including anxiety and pleasure. == Mekkaniżmi ta' difiża == Many small reptiles, such as snakes and lizards, that live on the ground or in the water are vulnerable to being preyed on by all kinds of carnivorous animals. Thus, avoidance is the most common form of defense in reptiles. At the first sign of danger, most snakes and lizards crawl away into the undergrowth, and turtles and crocodiles will plunge into water and sink out of sight. === Mimetizzazzjoni u twissija === Reptiles tend to avoid confrontation through camouflage. Two major groups of reptile predators are birds and other reptiles, both of which have well-developed color vision. Thus the skins of many reptiles have cryptic coloration of plain or mottled gray, green, and brown to allow them to blend into the background of their natural environment. Aided by the reptiles' capacity for remaining motionless for long periods, the camouflage of many snakes is so effective that people or domestic animals are most typically bitten because they accidentally step on them. When camouflage fails to protect them, blue-tongued skinks will try to ward off attackers by displaying their blue tongues, and the frill-necked lizard will display its brightly colored frill. These same displays are used in territorial disputes and during courtship. If danger arises so suddenly that flight is useless, crocodiles, turtles, some lizards, and some snakes hiss loudly when confronted by an enemy. Rattlesnakes rapidly vibrate the tip of the tail, which is composed of a series of nested, hollow beads to ward off approaching danger. In contrast to the normal drab coloration of most reptiles, the lizards of the genus ''Heloderma'' (the Gila monster and the beaded lizard) and many of the coral snakes have high-contrast warning coloration, warning potential predators they are venomous. A number of non-venomous North American snake species have colorful markings similar to those of the coral snake, an oft cited example of Batesian mimicry. === Difiża alternattiva fis-sriep === Camouflage does not always fool a predator. When caught out, snake species adopt different defensive tactics and use a complicated set of behaviors when attacked. Some species, like cobras or hognose snakes, first elevate their head and spread out the skin of their neck in an effort to look large and threatening. Failure of this strategy may lead to other measures practiced particularly by cobras, vipers, and closely related species, which use venom to attack. The venom is modified saliva, delivered through fangs from a venom gland. Some non-venomous snakes, such as American hognose snakes or European grass snake, play dead when in danger; some, including the grass snake, exude a foul-smelling liquid to deter attackers. === Difiża fil-kukkudrilli === When a crocodilian is concerned about its safety, it will gape to expose the teeth and tongue. If this does not work, the crocodilian gets a little more agitated and typically begins to make hissing sounds. After this, the crocodilian will start to change its posture dramatically to make itself look more intimidating. The body is inflated to increase apparent size. If absolutely necessary, it may decide to attack an enemy. Some species try to bite immediately. Some will use their heads as sledgehammers and literally smash an opponent, some will rush or swim toward the threat from a distance, even chasing the opponent onto land or galloping after it. The main weapon in all crocodiles is the bite, which can generate very high bite force. Many species also possess canine-like teeth. These are used primarily for seizing prey, but are also used in fighting and display. === Bdil tal-qxur u riġenerazzjoni tad-denb === Geckos, skinks, and some other lizards that are captured by the tail will shed part of the tail structure through a process called autotomy and thus be able to flee. The detached tail will continue to thrash, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. The detached tails of leopard geckos can wiggle for up to 20 minutes. The tail grows back in most species, but some, like crested geckos, lose their tails for the rest of their lives. In many species the tails are of a separate and dramatically more intense color than the rest of the body so as to encourage potential predators to strike for the tail first. In the shingleback skink and some species of geckos, the tail is short and broad and resembles the head, so that the predators may attack it rather than the more vulnerable front part. Reptiles that are capable of shedding their tails can partially regenerate them over a period of weeks. The new section will however contain cartilage rather than bone, and will never grow to the same length as the original tail. It is often also distinctly discolored compared to the rest of the body and may lack some of the external sculpting features seen in the original tail. == Rabtiet mal-bniedem == === Fil-kulturi u fir-reliġjonijiet === Dinosaurs have been widely depicted in culture since the English palaeontologist Richard Owen coined the name ''dinosaur'' in 1842. As soon as 1854, the Crystal Palace Dinosaurs were on display to the public in south London. One dinosaur appeared in literature even earlier, as Charles Dickens placed a ''Megalosaurus'' in the first chapter of his novel ''Bleak House'' in 1852. The dinosaurs featured in books, films, television programs, artwork, and other media have been used for both education and entertainment. The depictions range from the realistic, as in the television documentaries of the 1990s and first decade of the 21st century, to the fantastic, as in the monster movies of the 1950s and 1960s. The snake or serpent has played a powerful symbolic role in different cultures. In Egyptian history, the Nile cobra adorned the crown of the pharaoh. It was worshipped as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra). In Greek mythology, snakes are associated with deadly antagonists, as a chthonic symbol, roughly translated as ''earthbound''. The nine-headed Lernaean Hydra that Hercules defeated and the three Gorgon sisters are children of Gaia, the earth. Medusa was one of the three Gorgon sisters who Perseus defeated. Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze. After killing her, Perseus gave her head to Athena who fixed it to her shield called the Aegis. The Titans are depicted in art with their legs replaced by bodies of snakes for the same reason: They are children of Gaia, so they are bound to the earth. In Hinduism, snakes are worshipped as gods, with many women pouring milk on snake pits. The cobra is seen on the neck of Shiva, while Vishnu is depicted often as sleeping on a seven-headed snake or within the coils of a serpent. There are temples in India solely for cobras sometimes called ''Nagraj'' (King of Snakes), and it is believed that snakes are symbols of fertility. In the annual Hindu festival of Nag Panchami, snakes are venerated and prayed to. In religious terms, the snake and jaguar are arguably the most important animals in ancient Mesoamerica. "In states of ecstasy, lords dance a serpent dance; great descending snakes adorn and support buildings from Chichen Itza to Tenochtitlan, and the Nahuatl word ''coatl'' meaning serpent or twin, forms part of primary deities such as Mixcoatl, Quetzalcoatl, and Coatlicue." In Christianity and Judaism, a serpent appears in Genesis to tempt Adam and Eve with the forbidden fruit from the Tree of Knowledge of Good and Evil. The turtle has a prominent position as a symbol of steadfastness and tranquility in religion, mythology, and folklore from around the world. A tortoise's longevity is suggested by its long lifespan and its shell, which was thought to protect it from any foe. In the cosmological myths of several cultures a ''World Turtle'' carries the world upon its back or supports the heavens. === Mediċina === Deaths from snakebites are uncommon in many parts of the world, but are still counted in tens of thousands per year in India. Snakebite can be treated with antivenom made from the venom of the snake. To produce antivenom, a mixture of the venoms of different species of snake is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Blood is then extracted; the serum is separated, purified and freeze-dried. The cytotoxic effect of snake venom is being researched as a potential treatment for cancers. '''Gila monsters''' produce compounds that reduce plasma glucose; one of these substances is now used in the anti-diabetes drug exenatide (Byetta), a glucagon-like peptide-1 (GLP-1) receptor agonist like semiglutide (Ozempic). Another toxin from Gila monster saliva has been studied for use as an anti-Alzheimer's drug. Geckos have also been used as '''folk medicine''', especially in China, without any evidence that they have any active compounds. Turtles have been used in Chinese traditional medicine for thousands of years, with every part of the turtle believed to have medical benefits (again, without scientific evidence). Growing demand for '''turtle meat''' has placed pressure on vulnerable wild populations of turtles. === Trobbija kummerċjali === Crocodiles are protected in many parts of the world, and are farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbags; crocodile meat is also considered a delicacy. The most commonly farmed species are the saltwater and Nile crocodiles. Farming has resulted in an increase in the saltwater crocodile population in Australia, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat. Crocodile leather is made into wallets, briefcases, purses, handbags, belts, hats, and shoes. Crocodile oil has been used for various purposes. Snakes are also farmed, primarily in East and Southeast Asia, and their production has become more intensive in the last decade. Snake farming has been troubling for conservation in the past as it can lead to overexploitation of wild snakes and their natural prey to supply the farms. However, farming snakes can limit the hunting of wild snakes, while reducing the slaughter of higher-order vertebrates like cows. The energy efficiency of snakes is higher than expected for carnivores, due to their ectothermy and low metabolism. Waste protein from the poultry and pig industries is used as feed in snake farms. Snake farms produce meat, snake skin, and antivenom. Turtle farming is another known but controversial practice. Turtles have been farmed for a variety of reasons, ranging from food to traditional medicine, the pet trade, and scientific conservation. Demand for turtle meat and medicinal products is one of the main threats to turtle conservation in Asia. Though commercial breeding would seem to insulate wild populations, it can stoke the demand for them and increase wild captures. Even the potentially appealing concept of raising turtles at a farm to release into the wild is questioned by some veterinarians who have had some experience with farm operations. They caution that this may introduce into the wild populations infectious diseases that occur on the farm, but have not (yet) been occurring in the wild. === Rettili fil-magħluq === A herpetarium is a zoological exhibition space for reptiles and amphibians. In the Western world, some snakes (especially relatively docile species such as the ball python and corn snake) are sometimes kept as pets. Numerous species of lizard are kept as pets, including bearded dragons, iguanas, anoles, and geckos (such as the popular leopard gecko and the crested gecko). Turtles and tortoises are increasingly popular pets, but keeping them can be challenging due to their particular requirements, such as temperature control, the need for UV light sources, and a varied diet. The long lifespans of turtles and especially tortoises mean they can potentially outlive their owners. Good hygiene and significant maintenance is necessary when keeping reptiles, due to the risks of ''Salmonella'' and other pathogens. Regular hand-washing after handling is an important measure to prevent infection. == Referenzi == [[Kategorija:Rettili]] [[Kategorija:Klassifikazzjoni xjentifika]] gc9p2lvfio6mbq4w8xvmjsxelfl33h7