Die Sphenodontia (Gr. für Keilzahnige) oder Rhynchocephalia (Gr. für Schnabelköpfe) sind ein Taxon echsenartiger, diapsider Reptilien. Ihre Blüte erlebten sie in der Trias und im Jura. Mit der Brückenechse (Sphenodon punctatus) kommen sie noch heute auf einigen Inseln vor der Küste Neuseelands vor. Der früheste Nachweis eines Sphenodontiers stammt aus der oberen Mitteltrias von Deutschland.
Sphenodontier waren kleine bis mittelgroße Echsen, die Pleurosaurier erreichten Längen von 75 Zentimetern, bei den Brückenechsen ist dies die Maximallänge. Die Wirbel sind amphicoel geformt (an beiden Enden eingebuchtet). Der Bau des Schädels ist konservativ, die Schädelfenster sind besonders groß. Die akrodonte Bezahnung (Zähne sitzen ohne Zahnwurzel auf der Oberkante der Kiefers) zeigen eine mannigfaltige Anpassung an unterschiedliche Nahrungsquellen. Der oberjurassische Sapheosaurus war zahnlos.
Die Rhynchocephalia waren einst ein Sammeltaxon, zu dem viele „primitive“, nicht näher verwandte Taxa, z. B. auch die Rhynchosauria, gezählt wurden. In der aktuell genutzten Systematik werden ihnen nur noch zwei Familien zugerechnet: die aquatischen, ausschließlich fossilen Pleurosauridae und die terrestrischen Sphenodontidae. Um Verwechslungen mit dem alten Konzept der Rhynchocephalia zu vermeiden, nutzen viele Autoren für diese beiden Familien nur mehr den Namen „Sphenodontia“. Die Sphenodontia werden mit ihrer Schwestergruppe, den Schuppenkriechtieren (Squamata), im Taxon Schuppenechsen (Lepidosauria) vereinigt.
Die ältesten bislang (Stand 2015) bekannten Überreste von Sphenodontiern, liegen in Form isolierter Kiefer (cf. Diphydontosaurus sp.) vor und stammen aus dem unteren Keuper (Erfurt-Formation, oberste Mitteltrias) von Vellberg in Baden-Württemberg.[1] Vollständigere Skelette, die denen rezenter Brückenechsen ähneln, sind aus der frühen Obertrias bekannt. Von der Obertrias bis zum Oberjura sind Sphenodontier weltweit verbreitet. Fossilien aus der Kreide sind selten, und aus dem Känozoikum gibt es ebenfalls nur wenige Funde, die alle auf Neuseeland und die Gattung Sphenodon beschränkt sind.[2]
Die Sphenodontia (Gr. für Keilzahnige) oder Rhynchocephalia (Gr. für Schnabelköpfe) sind ein Taxon echsenartiger, diapsider Reptilien. Ihre Blüte erlebten sie in der Trias und im Jura. Mit der Brückenechse (Sphenodon punctatus) kommen sie noch heute auf einigen Inseln vor der Küste Neuseelands vor. Der früheste Nachweis eines Sphenodontiers stammt aus der oberen Mitteltrias von Deutschland.
Mayroong kaugnay na impormasyon sa Wikispecies ang Rhynchocephalia
Ang Rhynchocephalia ay isang order ng tulad ng butiking mga reptilya na kinabibilangan lamang ng isang nabubuhay na henus na tuatara(Sphenodon) at tanging dalawang nabubuhay na espesye. Sa kabila ng kakulangan sa dibersidad, ang Rhynchocephalia sa isang panahong ay kinabibilangan ng isang malaking bilang ng mga henera sa ilang mga pamilya at kumakatawan sa lipi na bumabalik sa era na Mesosoiko. Maraming mga niche na tinitirhan ngayon ng mga butiki ay tinirhan ng mga sphenodontian sa panahong ito. Mayroon isang matagumpay na pangkat ng mga pang-tubig na sphenodontian na kilala bilang mga pleurosauro na mapapansing iba sa mga nabubuhay na tuatara.
Rhynchocephalia (ଇଂରାଜୀ: Sphenodontia) ଡାଇନୋସର ବଂଶର ଜୀବ ଅଟେ ।[୧] ଏହି ଜୀବଟି ବର୍ତ୍ତମାନ ବିଲୁପ୍ତ ।
Ang Rhynchocephalia ay isang order ng tulad ng butiking mga reptilya na kinabibilangan lamang ng isang nabubuhay na henus na tuatara(Sphenodon) at tanging dalawang nabubuhay na espesye. Sa kabila ng kakulangan sa dibersidad, ang Rhynchocephalia sa isang panahong ay kinabibilangan ng isang malaking bilang ng mga henera sa ilang mga pamilya at kumakatawan sa lipi na bumabalik sa era na Mesosoiko. Maraming mga niche na tinitirhan ngayon ng mga butiki ay tinirhan ng mga sphenodontian sa panahong ito. Mayroon isang matagumpay na pangkat ng mga pang-tubig na sphenodontian na kilala bilang mga pleurosauro na mapapansing iba sa mga nabubuhay na tuatara.
Tiqerɣenbubin (Assaɣ ussnan: Rhynchocephalia) d tafesna n temraradin anda llant snat Kan n telmas ttidirent deg tmurt n Nyuzilanda.
Tuatara (Rhynchocepalia) nyaéta kelompok réptil langka nu nempatan pulo-pulo babatuan leupas pantai Selandia Baru.[1] Nepi ka ayeuna, tuatara mangrupa kelompok reptil pangsaeutik jenisna, ngan aya dua spésiés nu hirup.[1] Tuatara baheulana leuwih loba jeung rupa-rupa ti batan ayeuna.[1] Bukti fosil nuduhkeun yén ieu sato sumebar nepi ka Eropa, Afrika, Amérika Kidul jeung Madagaskar.[1] Aya sahenteuna 24 genus nu béda tina tuatara ngan lolobana geus laleungit antara 100 juta taun ka tukang.[1] Hal éta nu ngajadikeun Rhynchocephalia (hulu pamatuk) disebuta ordo primitif, réptil kawas kadal asal trias nu sok disebut fosil hirup.[2]
Tuatara mangrupa réptil semi nokturnal nu nempatan leuweung pantai di mana maranéhna néangan dahareun sakurilingeun sayangna jeung ngadahar endog manuk, hayam, invertebrata, amfibi, jeung réptil leutik.[1] Ku sabab ieu sato mangrupa sato getih tiis nu hirup di habitat nu alus, tuatara miboga tingkat métabolisme nu handap.[1] Maranéhna tumuwuh laun jeung miboga umur nu panjang.[1]
Tuatara (Rhynchocepalia) nyaéta kelompok réptil langka nu nempatan pulo-pulo babatuan leupas pantai Selandia Baru. Nepi ka ayeuna, tuatara mangrupa kelompok reptil pangsaeutik jenisna, ngan aya dua spésiés nu hirup. Tuatara baheulana leuwih loba jeung rupa-rupa ti batan ayeuna. Bukti fosil nuduhkeun yén ieu sato sumebar nepi ka Eropa, Afrika, Amérika Kidul jeung Madagaskar. Aya sahenteuna 24 genus nu béda tina tuatara ngan lolobana geus laleungit antara 100 juta taun ka tukang. Hal éta nu ngajadikeun Rhynchocephalia (hulu pamatuk) disebuta ordo primitif, réptil kawas kadal asal trias nu sok disebut fosil hirup.
Rhynchocephalia (/ˌrɪŋkoʊsɪˈfeɪliə/; lit. 'beak-heads') is an order of lizard-like reptiles that includes only one living species, the tuatara (Sphenodon punctatus) of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse group including a wide array of ecologies. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved a worldwide distribution by the Early Jurassic.[1] Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.
Many of the niches occupied by lizards today were held by sphenodontians during the Triassic and Jurassic, although lizard diversity began to overtake sphenodontian diversity in the Cretaceous, and they had disappeared almost entirely by the beginning of the Cenozoic. While the modern tuatara is primarily carnivorous, there were also sphenodontians with omnivorous (Opisthias), herbivorous (Eilenodontinae), and durophagous (Oenosaurus) lifestyles. There were even several successful groups of aquatic sphenodontians, such as pleurosaurs and Ankylosphenodon.[2]
Tuatara were originally classified as agamid lizards when they were first described by John Edward Gray in 1831. They remained misclassified until 1867, when Albert Günther of the British Museum noted features similar to birds, turtles, and crocodiles. He proposed the order Rhynchocephalia (meaning "beak head") for the tuatara and its fossil relatives.[3] In 1925 Samuel Wendell Williston proposed the Sphenodontia to include only tuatara and their closest fossil relatives.[4] Sphenodon is derived from Greek σφήν sphen 'wedge' and ὀδούς odous 'tooth'.[5][6][7] Many disparately related species were subsequently added to the Rhynchocephalia, resulting in what taxonomists call a "wastebasket taxon". These include the superficially similar (both in shape and name) but unrelated rhynchosaurs, which lived in the Triassic.[4] These were resolved after use of computer based cladistics, which showed the core sphenodontian grouping to be monophyletic.[8]
Sphenodonts, and their sister group Squamata (which includes lizards, snakes and amphisbaenians), belong to the superorder Lepidosauria, the only surviving taxon within Lepidosauromorpha.
Squamates and sphenodontians have a number of shared traits (synapomorphies), including fracture planes within the tail vertebrae allowing caudal autotomy (loss of the tail-tip when threatened), transverse cloacal slits, an opening in the pelvis known as the thyroid fenestra, the presence of extra ossification centres in the limb bone epiphyses, a knee joint where a lateral recess on the femur allows the articulation of the fibula, the development of a sexual segment of the kidney, and a number of traits of the feet bones, including a fused astralago-calcaneun and enlarged fourth distal tarsal, which creates a new joint, along with a hooked fifth metatarsal.[9]
Like some squamates, the tuatara retains a parietal eye, which has been lost in the other groups of extant reptiles, the turtles and archosaurs.[10] Rhynchocephalians are distinguished from squamates by a number of traits, including the retention of gastralia (rib-like bones present in the belly of the body, ancestrally present in tetrapods and also present in living crocodilians).[11] The complete lower temporal bar (caused by the fusion of the jugal and quadtrate/quadratojugal bones) of the tuatara, often considered a primitive feature, is actually a derived feature among sphenodontians, with the most primitive lepidosauromorphs and rhynchocephalians having an open lower temporal fenestra.[12][13] Unlike squamates, but similar to the majority of birds, the tuatara lacks a penis. This is a secondary loss, as a penis or squamate-like hemipenes were probably present in the last common ancestor of rhynchocephalians and squamates.[14]
The dentition of most rhynchocephalians is described as acrodont (the condition where the teeth are attached to the crest of the jaw bone, and lack roots), similar to those of acrodontan lizards like agamids. The term "acrodont" has also been used in reference to the absence of tooth replacement or the extent of bone growth around the teeth, causing terminological confusion. The teeth of living tuatara have no roots and are not replaced, and are extensively fused to the jaw bone. The teeth of Gephyrosaurus are pleurodont (teeth are weakly attached to the inner part of the mandible with no sockets, and replaced throughout life), like those of most squamates, and this is thought to be the ancestral condition of Lepidosauria. The most primitive sphenodontians have a combination of both pleurodont and acrodont teeth. Some rhyncocephalians differ from these conditions, with Ankylosphenodon having teeth that continue deeply into the jaw bone, and are fused to the bone at the base of the socket (ankylothecodont).[15]
Rhynchocephalians possess palatal dentition (teeth present on the bones of the roof of the mouth). In most rhynchocephalians, the teeth present on the pterygoid bone are lost, but the lateral tooth row present on the palatine bones are enlarged, and orientated parallel to the teeth of the maxilla. During biting, the teeth of the dentary in the lower jaw slot between the maxillary and palatine tooth rows. This arrangement, which is unique among amniotes, permits three point bending of food items,[16] and in combination with propalinal movement (back and forward motion of the lower jaw) allows for a shearing bite.[17][18]
While the grouping of Rhynchocephalia is well supported, the relationships of many taxa to each other are uncertain, varying substantially between studies.[19] In modern cladistics, the clade Sphenodontia includes all rhynchocephalians other than Gephyrosaurus (as well as some other related genera) which has been found to be more closely related to squamates in some analyses.[8] In 2018, two major clades within Sphenodontia were defined, the infraorder Eusphenodontia which is defined by the least inclusive clade containing Polysphenodon, Clevosaurus hudsoni and Sphenodon, which is supported by the presence of three synapomorphies, including the presence of clearly visible wear facets on the teeth of the dentary or maxilla, the premaxillary teeth are merged into a chisel like structure, and the palatine teeth are reduced to a single tooth row, with the presence of an additional isolated tooth. The unranked clade Neosphenodontia (previously informally referred to as the "eupropalinals", in reference to the back and forward motion in the mouth during mastication), is defined as the most inclusive clade containing Sphenodon but not Clevosaurus hudsoni, which is supported by the presence of six synapomorphies, including the increased relative length of the antorbital region of the skull (the part of the skull forward of the eye socket), reaching 1/4 to 1/3 of the total skull length, the posterior (hind) edge of the parietal bone is only slightly curved inward, the parietal foramen is found at the same level or forward of the anterior border of the supratemporal fenestra (an opening of the skull), the palatine teeth are further reduced from the condition in eusphenodontians to a single lateral tooth row, the number of pterygoid tooth rows are reduced to one or none, and the posterior border of the ischium is characterised by a distinctive process.[20] In 2021 the clade Acrosphenodontia was defined, which is less inclusive than Sphenodontia and more inclusive than Eusphenodontia, and includes all sphenodontians with fully acrodont dentition, excluding basal partially acrodont sphenodontians.[21] In 2022 the extinct clade Leptorhynchia was defined, including a variety of aquatically adapted neosphenodontians, characteristed by the elongation of the fourth metacarpal, the presence of a posterior process on the ischium, and the antorbital region of the skulls is between a third and a quarter of the total skull length.[22]
The family Sphenodontidae has been used to include the tuatara and its closest relatives within Rhynchocephalia. However the grouping has lacked a formal definition, with the included taxa varying substantially between analyses.[8] The closest relatives of the tuatara are placed in the clade Sphenodontinae, which are characterised by a completely closed temporal bar.[13]
Rhynchocephalians were once considered to be a morphologically conservative group with little diversity. However, discoveries in recent decades have disputed this, finding a wide array of diversity within the clade.[3][16] Early rhynchocephalians possess small ovoid teeth designed for piercing, and were probably insectivores.[23] Amongst the most distinct rhynchocephalians are the pleurosaurs, known from the Jurassic of Europe, which were adapted for marine life, with elongated snake-like bodies with reduced limbs, with the specialised Late Jurassic genus Pleurosaurus having an elongated triangular skull highly modified from those of other rhynchocephalians.[24] Several other lineages of rhyncocephalians have been suggested to have had semi-aquatic habits.[25] Eilenodontines are thought to have been herbivorous, with batteries of wide teeth with thick enamel used to process plant material.[26] The sapheosaurids, such as Oenosaurus and Sapheosaurus from the Late Jurassic of Europe possess broad tooth plates unique amongst tetrapods, and are thought to have been durophagous, with the tooth plates being used to crush hard shelled organisms.[27][8]
Rhynchocephalia is estimated to have diverged from Squamata between the Middle Permian and earliest Triassic, between 270 and 252 million years ago.[8] The oldest known remains of rhynchocephalians are indeterminate jaw fragments from the Erfurt Formation near Vellberg in Southern Germany, dating to the Ladinian stage of the Middle Triassic, around 238-240 million years old.[1] Rhynchocephalians reached a worldwide distribution across Pangaea by the end of the Triassic, with the Late Triassic-Early Jurassic genus Clevosaurus having 10 species across Asia, Africa, Europe, North and South America.[28] The earliest rhynchocephalians were small animals, but by the Late Triassic the group had evolved a wide range of body sizes.[29] During the Jurassic rhynchocephalians reached their apex of morphological diversity, including specialised herbivorous and aquatic forms.[3] The only record of Rhynchocephalians from Asia are indeterminate remains of Clevosaurus from the Early Jurassic (Sinemurian) aged Lufeng Formation of Yunnan, China. Rhynchocephalians are noticeably absent from younger localities in the region, despite the presence of favourable preservation conditions.[30]
Rhynchocephalians disappeared from North America and Europe after the Early Cretaceous,[31] and were absent from North Africa[32] and northern South America[33] by the early Late Cretaceous. The cause of the decline of Rhynchocephalia remains unclear, but has often been suggested to be due to competition with advanced lizards and mammals.[34] They appear to have remained diverse in high-latitude southern South America during the Late Cretaceous, where lizards remained rare, with their remains outnumbering terrestrial lizards by a factor of 200.[32] An indeterminate rhynchocephalian is known from the latest Cretaceous of Insular India.[35] The youngest known remains of rhynchocephalians outside of New Zealand are those of Kawasphenodon peligrensis from the early Paleocene (Danian) of Patagonia, shortly after the Cretaceous–Paleogene extinction event.[36] Indeterminate sphenodontine jaw fragments bearing teeth are known from the early Miocene (19-16 million years ago) St Bathans fauna, New Zealand, that are indistinguishable from those of the living tuatara. It is unlikely that the ancestors of the tuatara arrived in New Zealand via oceanic dispersal, and it is thought that they were already present in New Zealand when it separated from Antarctica between 80 and 66 million years ago.[34]
Skull reconstruction of Gephyrosaurus a possible basal rhyncocephalian
Reconstruction of the skull of Diphydontosaurus a basal member of Sphenodontia
Reconstruction of the skulls of Clevosaurus hudsoni (A) and Clevosaurus cambrica (B)
Skulls of Priosphenodon, a herbivorous member of Eilenodontinae
Reconstruction of the skull of Priosphenodon in lateral view
Reconstruction of the skull of Navajosphenodon, an early member of Sphenodontinae
Skull of the tuatara in various views
The following is a cladogram of Rhynchocephalia after Rauhut et al., 2012.[27]
Rhynchocephalia Sphenodontia †Pleurosauridae SphenodontidaeSphenodon (Tuatara)
†Opisthodontia †EilenodontinaeRhynchocephalia (/ˌrɪŋkoʊsɪˈfeɪliə/; lit. 'beak-heads') is an order of lizard-like reptiles that includes only one living species, the tuatara (Sphenodon punctatus) of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse group including a wide array of ecologies. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved a worldwide distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.
Many of the niches occupied by lizards today were held by sphenodontians during the Triassic and Jurassic, although lizard diversity began to overtake sphenodontian diversity in the Cretaceous, and they had disappeared almost entirely by the beginning of the Cenozoic. While the modern tuatara is primarily carnivorous, there were also sphenodontians with omnivorous (Opisthias), herbivorous (Eilenodontinae), and durophagous (Oenosaurus) lifestyles. There were even several successful groups of aquatic sphenodontians, such as pleurosaurs and Ankylosphenodon.
Los esfenodontos (Sphenodontia) o rincocéfalos (Rhynchocephalia) son un orden de saurópsidos (reptiles) lepidosaurios que incluye un solo género actual, Sphenodon, con tres especies, conocidas con el nombre común de tuátaras, limitadas a Nueva Zelanda.
A pesar de ello, se conocen numerosos géneros extintos, ya que se trata de un linaje que se remonta al Mesozoico.
La clasificación según Wu (1994), Evans et al. (2001), y Apesteguia & Novas (2003).[1]
En 2012 se ha descrito Sphenocondor, un nuevo esfenodonte basal del Jurásico medio de Patagonia.[3]
Los estudios genéticos revelan las siguientes relaciones filogenéticas para los tuátaras con respecto a otros reptiles y tetrápodos vivos (incluido las secuencias proteicas obtenidas de Tyrannosaurus rex y Brachylophosaurus canadensis). Junto con el orden Squamata constituye el clado Lepidosauria.[4][5][6][7]
Tetrapoda Amniota Sauropsida LepidosauriaSphenodontia
Tyrannosauroidea (Tyrannosaurus) 
Ornithischia (Brachylophosaurus) 
Datos: Q15099738
Especies: Rhynchocephalia
Los esfenodontos (Sphenodontia) o rincocéfalos (Rhynchocephalia) son un orden de saurópsidos (reptiles) lepidosaurios que incluye un solo género actual, Sphenodon, con tres especies, conocidas con el nombre común de tuátaras, limitadas a Nueva Zelanda.
A pesar de ello, se conocen numerosos géneros extintos, ya que se trata de un linaje que se remonta al Mesozoico.
Errinkozefalioak (Rhynchocephalia) Triasikoan sortutako narrasti lepidosaurioen ordena da, gaur egun ordezkari bakarra duena, hots, Zeelanda Berriko tuatara, zeina bi hezur-arku kranial edukitzeagatik ezaugarritzen den.[1]
Mesozoo garaian bizi izan ziren eta musker itxurako gorputza zuten narrastiak dira. Arrek ez zuten sexu organorik. Buru-handiak eta mokodunak ziren. Bizkarrean zehar gandor arantzadun bat zuten.[2]
Hona hemen Wu-k (1994),[3] Evans et al.-ek (2001),[4] eta Apesteguia & Novas-ek (2003).[5][6] proposaturiko kladograma:
RhynchocephaliaSphenodon (Tuatara)
{{Expansion depth limit exceeded|1=Priosphenodon
2=Eilenodon }}Errinkozefalioak (Rhynchocephalia) Triasikoan sortutako narrasti lepidosaurioen ordena da, gaur egun ordezkari bakarra duena, hots, Zeelanda Berriko tuatara, zeina bi hezur-arku kranial edukitzeagatik ezaugarritzen den.
Mesozoo garaian bizi izan ziren eta musker itxurako gorputza zuten narrastiak dira. Arrek ez zuten sexu organorik. Buru-handiak eta mokodunak ziren. Bizkarrean zehar gandor arantzadun bat zuten.
Alkuliskot eli tuatarat (Rhynchocephalia) on yksi matelijoiden neljästä elossa olevasta lahkosta. Lahkosta on tähän päivään selvinnyt hengiissä vain yksi laji, Uudessa Seelannissa elävä tuatara. Nimestään huolimatta alkuliskot eivät ole läheistä sukua liskoille tai käärmeille vaikka ne ovatkin niiden lähimmät sukulaiset nykyään elossa olevista lajeista.
Alkuliskot on hyvin vanha matelijoiden ryhmä. Vanhin alkuliskon fossiili on löydetty Saksasta ja se on ajoitettu keskiselle triaskaudelle noin 240 miljoonaa vuotta sitten.[1] Tuatarat ovat "elävä fossiili", mikä näkyy monessa niiden piirteissä. Tuataran aivot ovat suunnilleen yhtä kehittyneet kuin sammakkoeläimillä ja sen sydän on primitiivisempi kuin millään muulla elävällä matelijalla.
Aiemmin nykyiset tuatarat jaoteltiin kahdeksi eri lajiksi niiden esiintymisalueen mukaan, mutta vuonna 2009 tehty tarkempi DNA-analyysi paljasti, että kyse on pikemminkin yhdestä ja samasta lajista.[2]
Aikaisemmassa luokittelussa Sphenodontia oli Rhynchocephalian synonyymi ja lahkoon luokiteltiin kolme heimoa, Sphenodontidae sekä sukupuuttoon kuolleet Gephyrosauridae ja Pleurosauridae.
Aiempi luokitteluNykyään Sphenodontia on alkuliskojen alalahko joka sulkee pois Gephyrosauruksen, mutta sisältää kaikki muut lajit.
Kladogrammi Rauhut et al., 2012 mukaan:
Sphenodon (Tuatarat)
Alkuliskot eli tuatarat (Rhynchocephalia) on yksi matelijoiden neljästä elossa olevasta lahkosta. Lahkosta on tähän päivään selvinnyt hengiissä vain yksi laji, Uudessa Seelannissa elävä tuatara. Nimestään huolimatta alkuliskot eivät ole läheistä sukua liskoille tai käärmeille vaikka ne ovatkin niiden lähimmät sukulaiset nykyään elossa olevista lajeista.
Les rhynchocéphales (Rhynchocephalia parfois Sphenodontia) sont un des deux ordres de lepidosauriens.
Ce groupe dont les plus anciens fossiles connus remontent au Trias ne comprend plus qu’une espèce actuelle, les sphénodons endémiques de Nouvelle-Zélande.
Le nom de Rhynchocéphale vient du grec ρυγχος / rynkos qui signifie bec et κεφαλε / kefale tête, en référence à la forme caractéristique du crâne « en bec ». Le nom de sphénodonte vient du grec σφήν / sphenos qui signifie coin, et ὀδούς / odont, désignant la dent. Les dents sur le prémaxillaire à l'avant du maxillaire, agissant avec leur bord tranchant comme un couteau, ont fusionné pour former une structure ressemblant à un bec[1].
Au sein des lépidosauriens ce groupe présente des caractères propres en particulier pour ce qui concerne la denture :
Selon Wu, 1994[3] Evans, Prasad & Manhas 2001[4] et Apesteguia & Novas, 2003[5] dans Mikko's Phylogeny Archive[6]
RhynchocephaliaLes rhynchocéphales (Rhynchocephalia parfois Sphenodontia) sont un des deux ordres de lepidosauriens.
Ce groupe dont les plus anciens fossiles connus remontent au Trias ne comprend plus qu’une espèce actuelle, les sphénodons endémiques de Nouvelle-Zélande.
Rhynchocephalia adalah ordo reptil mirip kadal yang mencakup hanya satu spesies hidup, tuatara (Sphenodon punctatus), yang hanya mendiami bagian dari Selandia Baru.[1] Meskipun kurangnya saat ini keragaman, Rhynchocephalia pada satu waktu termasuk beragam genera di beberapa famili, dan merupakan keturunan yang membentang ke Era Mesozoikum. Banyak dari relung ditempati oleh kadal saat ini dipegang oleh sphenodontia. Bahkan ada sekelompok sukses sphenodontia air yang dikenal sebagai pleurosaurus.
Rhynchocephalia adalah ordo reptil mirip kadal yang mencakup hanya satu spesies hidup, tuatara (Sphenodon punctatus), yang hanya mendiami bagian dari Selandia Baru. Meskipun kurangnya saat ini keragaman, Rhynchocephalia pada satu waktu termasuk beragam genera di beberapa famili, dan merupakan keturunan yang membentang ke Era Mesozoikum. Banyak dari relung ditempati oleh kadal saat ini dipegang oleh sphenodontia. Bahkan ada sekelompok sukses sphenodontia air yang dikenal sebagai pleurosaurus.
I rincocefali (Rhynchocephalia, che in greco significa testa a becco) sono un ordine di rettili considerati fossili viventi per le loro caratteristiche arcaiche. L'unico rappresentante vivente di quest'ordine è il tuatara (Sphenodon punctatus)[1].
Rappresentanti fossili di quest'ordine sono conosciuti fin dal Triassico, oltre 200 milioni di anni fa, al tempo in cui ha avuto inizio la stirpe dei dinosauri. L'ordine, con l'eccezione del tuatara, si è però definitivamente estinto circa 60 milioni di anni fa. I rincocefali viventi, come molti di quelli estinti, hanno aspetto simile a lucertole.
I primi rincocefali noti erano piccoli animali non più lunghi di una ventina di centimetri, i cui resti fossili sono stati ritrovati principalmente in Gran Bretagna. Tra le forme più note, da ricordare Planocephalosaurus e Clevosaurus. Vi furono molte altre specie durante il Triassico e il Giurassico, distinte principalmente per caratteristiche del cranio (ad es. Homeosaurus e Sapheosaurus, privo di denti). In generale, la corporatura era quella di lucertole tozze.
Alcune forme, però, si discostavano notevolmente da questo piano corporeo: in particolare sono notevoli le specie della famiglia Pleurosauridae, dotate di corpi allungatissimi adatti al nuoto, e alcuni rincocefali rinvenuti in Messico (Pamizinsaurus, Ankylosphenodon). Nel Cretaceo gli sfenodonti iniziarono a declinare, per poi scomparire dalla documentazione fossile per tutto il Cenozoico. Tra gli ultimi rincocefali del Cretaceo, da ricordare il grande Priosphenodon, mentre in Italia è noto Derasmosaurus. Gli unici "relitti" di questa fauna un tempo diffusa sono i tuatara della Nuova Zelanda.
Questa classificazione si basa sugli studi di Wu (1994),[2] Evans et al. (2001),[3] Apesteguia & Novas (2003)[4][5] e Evans & Borsuk−Białynicka (2009).[6]
I rincocefali (Rhynchocephalia, che in greco significa testa a becco) sono un ordine di rettili considerati fossili viventi per le loro caratteristiche arcaiche. L'unico rappresentante vivente di quest'ordine è il tuatara (Sphenodon punctatus).
Rhynchocephalia (também chamada de Sphenodontida ou Sphenodontia) é uma ordem de répteis que foram numerosos durante a Era Mesozóica, mas que hoje incluem apenas um gênero vivo: Sphenodon, conhecido popularmente como tuatara, que vive na Nova Zelândia.[1]
Os animais dessa ordem não são lagartos, mas sim parentes próximos destes. A ordem Rhynchocephalia forma, juntamente à ordem Squamata (lagartos), a superordem Lepidosauria.
Os esfenodontes e seu grupo irmão, Squamata (que inclui lagartos, cobras e anfisbenas), pertencem à superordem Lepidossauria, o único táxon sobrevivente dentro de Lepidosauromorpha. Squamates e sphenodonts mostram autotomia caudal (perda da ponta da cauda quando ameaçada) e têm fendas de cloaca transversais. [4] A origem dos esfenodontes provavelmente está perto da divisão entre os Lepidosauromorpha e os Archosauromorpha. Embora se assemelhem a lagartos, a semelhança é superficial, porque o grupo possui várias características únicas entre os répteis. A forma típica de lagarto é muito comum nos primeiros amniotas; o mais antigo fóssil conhecido de um réptil, Hylonomus, assemelha-se a um lagarto moderno. R.L. Ditmars, Litt.D, diz; "Os Tuatara se assemelham a lagartos modernos de corpo robusto, que poderíamos chamar de iguanas; essa semelhança é ainda mais intensificada por uma fileira de espinhos nas costas. É azeitona escura, os lados polvilhados com pontos pálidos. O olho tem um Os grandes espécimes têm dois metros e meio de comprimento, enquanto a semelhança superficial pode agrupar esse réptil com lagartos, seu esqueleto e anatomia mostram que ele pertence a uma parte diferente de uma classificação técnica.
Selon Wu, 1994[2] Evans, Prasad & Manhas 2001[3] e Apesteguia & Novas, 2003[4] em Mikko's Phylogeny Archive[5]
Rhynchocephalia unnamedUma característica única do tuatara é um "terceiro olho" no topo da cabeça. O "olho" tem retina, lente e terminações nervosas, mas não é usado para ver. É visível abaixo de pele de tuatara juvenil depois de alguns meses fica coberto de escamas e pigmento. O único olho é sensível à luz e acredita-se que ele ajude o juiz a julgar a hora do dia ou a estação do ano. Além disso, ele possui duas fileiras paralelas de dentes na mandíbula superior, e a folga entre essas fileiras é onde os dentes da mandíbula inferior se encaixam para executar um movimento especial de moagem / corte para esmagar a presa. Além disso, o tuatara tem um crânio diapside, mas falta uma barra temporal inferior completa, que o separa de outras espécies, bem como a dentição acrodonte e o par de dentes incisivos. A forma do dente foi originalmente projetada para uma dieta estritamente insetívora com dentes perfurantes. Mais tarde, os dentes se tornaram mais diversificados para vários ancestrais dos tuatara, que incluíam herbívoros, carnívoros e onívoros. Os dentes eram complexos o suficiente para esmagar cascas de caranguejo, enquanto outros mantinham crescimento contínuo na mandíbula inferior para a quebra do material vegetal. Sua estrutura dental atual é especializada para triturar as presas após a captura. O registro fóssil mostra a linhagem tuatara separando-se dos escamas há aproximadamente 240 milhões de anos.
Os Tuatara foram originalmente classificados como lagartos em 1831, quando a espécie foi descoberta por John Edward Gray e o British Museum recebeu uma caveira. Os registros fósseis mostram que eles existem desde o Triássico Médio, aproximadamente 240 milhões de anos atrás. O tuatara é freqüentemente considerado um fóssil vivo, que está sendo desafiado por pessoas que os consideram um modelo de adaptação evolucionária que estão bem adaptados às suas condições atuais e não são um grupo imutável. O nome tuatara foi dado ao vertebrado pelo povo maori, o povo indígena polinésio da Nova Zelândia. A palavra tuatara significa "picos nas costas" ou "costas espinhosas", por sua óbvia crista dorsal de escamas pontiagudas descendo pela cabeça, costas e cauda. O gênero permaneceu classificado erroneamente até 1867, quando Albert Günther, do British Museum, notou características semelhantes a pássaros, tartarugas e crocodilos. [9] Muitas espécies diferentes relacionadas foram adicionadas subsequentemente à Rhynchocephalia, resultando no que os taxonomistas chamam de "taxon de cesta de lixo". Williston propôs a Sphenodontia para incluir apenas tuatara e seus parentes fósseis mais próximos em 1925. [10] Sphenodon é derivado do grego para "cunha" (σφήν / sphen) e "dente" (ὀδούς / odous). No entanto, hoje Rhynchocephalia é usado para incluir Gephyrosaurus e Sphenodontia, enquanto Sphenodontia exclui o primeiro.
Rhynchocephalia (também chamada de Sphenodontida ou Sphenodontia) é uma ordem de répteis que foram numerosos durante a Era Mesozóica, mas que hoje incluem apenas um gênero vivo: Sphenodon, conhecido popularmente como tuatara, que vive na Nova Zelândia.
Os animais dessa ordem não são lagartos, mas sim parentes próximos destes. A ordem Rhynchocephalia forma, juntamente à ordem Squamata (lagartos), a superordem Lepidosauria.
Rhynchocephalia Günther, 1867[1]
Ареал
Клювоголо́вые, или хоботноголовые[2][3] (лат. Rhynchocephalia), — один из четырёх современных отрядов пресмыкающихся. Представители отряда обладают рядом архаичных признаков, в частности, развитым теменным глазом. Современные представители — гаттерии, населяющие острова Новой Зеландии. До недавнего времени выделяли два вида ныне живущих гаттерий (Sphenodon punctatus и Sphenodon guntheri), однако в последние годы их самостоятельность поставлена под сомнение[4].
В настоящее время в отряд включают 43 ископаемых и 2 современных вида, которые объединяют три семейства[5]. Большинство видов описаны в составе монотипипических родов[5]:
Отдельные представители
Это заготовка статьи по герпетологии. Вы можете помочь проекту, дополнив её. Клювоголо́вые, или хоботноголовые (лат. Rhynchocephalia), — один из четырёх современных отрядов пресмыкающихся. Представители отряда обладают рядом архаичных признаков, в частности, развитым теменным глазом. Современные представители — гаттерии, населяющие острова Новой Зеландии. До недавнего времени выделяли два вида ныне живущих гаттерий (Sphenodon punctatus и Sphenodon guntheri), однако в последние годы их самостоятельность поставлена под сомнение.
喙頭目（學名：Rhynchocephalia），也稱喙頭蜥目，是形似蜥蜴的蜥形綱動物的一個目。今僅存楔齒蜥科下楔齒蜥屬2種。
1831年，喙頭蜥的頭骨被送至大英博物館，因被當成一種蜥蜴，而使整個屬被錯誤分類。[失效連結][2]
1867年，大英博物館的阿爾伯特·甘瑟（Albert Günther）注意到喙頭蜥與鳥、龜和鱷的相似點，建立了喙頭目以包含喙頭蜥與相關的化石種。[失效連結][3] 然而許多無關的種隨後都被添加到喙頭目下。[4]
1925年， 塞繆爾·溫德爾·威利斯頓（Samuel Wendell Williston）提出新的楔齒蜥類（Sphenodontia），僅包含現今生存的楔齒蜥與相關的化石種，以區別於混雜的喙頭目。[4]
如今喙头目的用法包含 Gephyrosaurus（英语：Gephyrosaurus） 與楔齒蜥類。[5][6]
以下是 Rauhut 等人於2012年提出的喙頭目的演化樹。[7]
喙頭目Gephyrosaurus
楔齒蜥類Diphydontosaurus
Planocephalosaurus
Homoeosaurus
Brachyrhinodon
Clevosaurus
PleurosauridaePalaeopleurosaurus
Pleurosaurus
Kallimodon
Sapheosaurus
楔齒蜥科Oenosaurus
Cynosphenodon
Zapatadon
OpisthodontiaOpisthias
EilenodontiniToxolophosaurus
Priosphenodon
Eilenodon
훼두목(喙頭目, Rhynchocephalia) 또는 옛도마뱀목(Sphenodontia)은 인룡의 일종이다. 과거에는 광범위한 과와 속, 종들이 딸려 있었으나, 그 중 현대에 생존하고 있는 것은 투아타라(Sphenodon punctatus)를 포함하여 2종뿐이다.
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