# Rhynchocephalia

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Order of reptiles

Not to be confused with [Rhynchosaur](/source/Rhynchosaur).

Rhynchocephalians Temporal range: Middle Triassic-Holocene ~244–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N The tuatara (Sphenodon punctatus), the only living rhynchocephalian Fossil of Vadasaurus, a rhynchocephalian from the Late Jurassic of Germany Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Superorder: Lepidosauria Order: Rhynchocephalia Günther 1867 Type species Sphenodon punctatus Gray, 1842 Subgroups See text

**Rhynchocephalia** ([/ˌrɪŋkoʊsɪˈfeɪliə/](https://en.wikipedia.org/wiki/Help:IPA/English); lit. 'beak-heads') is an [order](/source/Order_(biology)) of lizard-like [reptiles](/source/Reptile) that includes only one living species, the [tuatara](/source/Tuatara) (*Sphenodon punctatus*) of [New Zealand](/source/New_Zealand). Despite its current lack of diversity, during the [Mesozoic](/source/Mesozoic) rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the [Middle Triassic](/source/Middle_Triassic) around 244 million years ago,[1] and they had achieved global distribution by the [Early Jurassic](/source/Early_Jurassic).[2] Most rhynchocephalians belong to the [suborder](/source/Order_(biology)) **Sphenodontia** ('wedge-teeth'). Their closest living relatives are [lizards](/source/Lizard) and [snakes](/source/Snake) in the order [Squamata](/source/Squamata), with the two orders being grouped together in the superorder [Lepidosauria](/source/Lepidosauria).

Rhynchocephalians are distinguished from squamates by a number of traits, including the retention of rib-like [gastralia](/source/Gastralia) bones in the belly, and a [proatlas](/source/Proatlas) bone in the neck as well as most rhynchocephalians having [acrodont](/source/Acrodont) teeth that are fused to the crests of the jaws (the latter also found among a small number of modern lizard groups like [agamids](/source/Agamidae)).

Once representing the world's dominant group of small reptiles, many of the niches occupied by lizards today were held by rhynchocephalians during the [Triassic](/source/Triassic%E2%80%93Jurassic_extinction_event) and [Jurassic](/source/Jurassic). Rhynchocephalians underwent a great decline during the [Cretaceous](/source/Cretaceous), and they had disappeared almost entirely by the beginning of the [Cenozoic](/source/Cenozoic). While the modern tuatara is primarily [insectivorous](/source/Insectivorous) and [carnivorous](/source/Carnivore), the diversity of the group also included the [herbivorous](/source/Herbivore) [eilenodontines](/source/Eilenodontinae), and there were other rhynchocephalians with specialised ecologies like the [durophagous](/source/Durophagous) [sapheosaurs](/source/Sapheosaurs). There were even successful groups of aquatic sphenodontians, such as the elongate-bodied [pleurosaurs](/source/Pleurosauridae).[3]

## Research history

[Tuatara](/source/Tuatara) were originally classified as [agamid](/source/Agamidae) [lizards](/source/Lizard) when they were first described by [John Edward Gray](/source/John_Edward_Gray) in 1831. They remained misclassified until 1867, when [Albert Günther](/source/Albert_C._L._G._G%C3%BCnther) of the British Museum noted features similar to birds, turtles, and crocodiles. He proposed the order Rhynchocephalia (from [Ancient Greek](/source/Ancient_Greek) ῥύγχος (**rhúnkhos**) 'beak' and κεφαλή (**kephalḗ**) 'head', meaning "beak head") for the tuatara and its fossil relatives.[4] In 1925, [Samuel Wendell Williston](/source/Samuel_Wendell_Williston) proposed the Sphenodontia to include only tuatara and their closest fossil relatives.[5] *Sphenodon* is derived from Ancient Greek σφήν (**sphḗn**) 'wedge' and ὀδούς (**odoús**) 'tooth'.[6][7][8] Many disparately related species were subsequently added to the Rhynchocephalia, resulting in what taxonomists call a "[wastebasket taxon](/source/Wastebasket_taxon)". These include the superficially similar (both in shape and name) but unrelated [rhynchosaurs](/source/Rhynchosaur), which lived in the [Triassic](/source/Triassic).[5] Studies in the 1970s and 1980s demonstrated that many rhynchosaurs were unrelated, with computer-based [cladistic](/source/Cladistic) analysis conducted in the 1980s providing a robust diagnosis for the definition of the group.[9]

## Anatomy

Skeleton of the tuatara (*Sphenodon punctatus*)

Rhynchocephalia and their sister group [Squamata](/source/Squamata) (which includes lizards, [snakes](/source/Snake) and [amphisbaenians](/source/Amphisbaenia)) belong to the superorder [Lepidosauria](/source/Lepidosauria), the only surviving taxon within [Lepidosauromorpha](/source/Lepidosauromorpha).

Squamates and rhynchocephalians have a number of shared traits ([synapomorphies](/source/Apomorphy_and_synapomorphy)), including fracture planes within the tail vertebrae allowing [caudal autotomy](/source/Autotomy#Reptiles_and_amphibians) (loss of the tail when threatened), transverse [cloacal](/source/Cloaca) slits, an opening in the pelvis known as the thyroid fenestra, the presence of extra [ossification centres](/source/Ossification_center) in the limb bone [epiphyses](/source/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](/source/Talus_bone)-[calcaneun](/source/Calcaneus) and enlarged fourth distal [tarsal](/source/Tarsus_(skeleton)), which creates a new joint, along with a hooked fifth [metatarsal](/source/Metatarsal_bones).[10]

Like some lizards, the tuatara possesses a [parietal eye](/source/Parietal_eye) (also called a pineal eye or a third eye) covered by scales at the top of the head formed by the parapineal organ, with an accompanying hole in the skull roof enclosed by the [parietal bones](/source/Parietal_bones), dubbed the "pineal foramen", which is also present in fossil rhynchocephalians. The parietal eye detects light (though it is probably not capable of detecting movement or forming images), monitoring the day-night and seasonal cycles, helping to regulate the [circadian rhythm](/source/Circadian_rhythm), among other functions.[11][12][13][14][15] While parietal eyes were widespread among early vertebrates, including early reptiles, they have been lost among most living groups.[13]

Rhynchocephalians are distinguished from squamates by a number of traits, including the retention of [gastralia](/source/Gastralium) (rib-like bones present in the belly of the body, ancestrally present in [tetrapods](/source/Tetrapod) and also present in living [crocodilians](/source/Crocodilia)).[16] 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](/source/Hemipenes) were probably present in the last common ancestor of rhynchocephalians and squamates.[17]

Skull of the basal rhynchocephalian *[Planocephalosaurus](/source/Planocephalosaurus)*, which has an open lower temporal fenestra

The complete lower temporal bar (caused by the fusion of the [jugal](/source/Jugal_bone) and [quadtrate](/source/Quadrate_bone)/[quadratojugal](/source/Quadratojugal_bone) bones of the skull) of the tuatara, often historically asserted to be a [primitive](/source/Primitive_(phylogenetics)) feature retained from earlier reptiles, is actually a [derived](/source/Derived_(phylogenetics)) feature among sphenodontians, with primitive lepidosauromorphs and many rhynchocephalians including the most primitive ones having an open lower [temporal fenestra](/source/Temporal_fenestra) without a temporal bar.[18][19] While often lacking a complete temporal bar, the vast majority of rhynchocephalians have a posteriorly directed [process](/source/Process_(anatomy)) (extension) of the jugal bone. All known rhynchocephalians lack the [splenial](/source/Splenial) bone present in the lower jaw of more primitive reptiles,[20] with the skulls of all members of Sphenodontia lacking [lacrimal bones](/source/Lacrimal_bones).[21] The majority of rhynchocephalians also have fused [frontal bones](/source/Frontal_bones) of the skull.[22][20] While early rhynchocephalians possessed a [tympanic membrane](/source/Tympanic_membrane) in the ear and a corresponding quadrate conch, similar to those found in lizards, these have been lost in the tuatara and likely other derived rhynchocephalians. This loss may be connected to the development of back and forth motion of the lower jaw.[23]

Skull of the tuatara in oblique view

The dentition of most rhynchocephalians, including the tuatara, is described as [acrodont](/source/Acrodont), which is associated with the condition of the teeth being attached to the crest of the jaw bone, lacking tooth replacement and having extensive bone growth fusing the teeth to the jaws resulting in the boundary between the teeth and bone being difficult to discern. This differs from the condition found in most lizards (except [acrodontans](/source/Acrodonta_(lizard))), which have [pleurodont](/source/Pleurodont) teeth which are attached to the shelf on the inward-facing side of the jaw, and are replaced throughout life. The teeth of the tuatara have no roots, though the teeth of some other rhynchocephalians possess roots (in addition, the precise technical meaning of term "acrodont" is somewhat ambiguous and the term is used with inconsistent meanings by different researchers).[24] The acrodont dentition appears to be a derived character of rhynchocephalians not found in more primitive lepidosauromorphs.[22] The most primitive rhynchocephalians have either pleurodont teeth or a combination of both pleurodont front and acrodont posterior teeth.[24][20] Some rhynchocephalians differ from these conditions, with *[Ankylosphenodon](/source/Ankylosphenodon)* having superficially acrodont teeth that continue deeply into the jaw bone, and are fused to the bone at the base of the socket (ankylothecodont).[24] In many derived sphenodontians, the [premaxillary](/source/Premaxillary) teeth at the front of the upper jaw are merged into a large chisel-like structure.[25]

Rhynchocephalians possess [palatal dentition](/source/Palatal_dentition) (teeth present on the bones of the roof of the mouth). Palatal teeth are ancestrally present in tetrapods, but have been lost in many groups. The earliest rhynchocephalians had teeth present on the [palatine](/source/Palatine_bone), [vomer](/source/Vomer_bone) and [pterygoid](/source/Pterygoid_bone) bones, though the vomer and/or the pterygoid teeth are lost in some groups, including the living tuatara, which only has palatine teeth.[26] A distinctive character found in all rhynchocephalians is the enlargement of the tooth row present on the palatine bones. While in other rhynchocephalians the palatine tooth row is oblique to the teeth of the [maxilla](/source/Maxilla), in members of Sphenodontinae (including the tuatara) and Eilenodontinae it is orientated parallel to the maxilla. In these groups, during biting, the teeth of the [dentary](/source/Mandible) in the lower jaw slot between the maxillary and palatine tooth rows. This arrangement, which is unique among amniotes, permits [three point bending](/source/Three-point_flexural_test) of food items,[27] and in combination with propalinal movement (back and forward motion of the lower jaw) allows for a shearing bite.[26][28]

Skeleton of the herbivorous [eilenodontine](/source/Eilenodontinae) *[Priosphenodon avelasi](/source/Priosphenodon)*, one of the largest known sphenodontians

The body size of rhynchocephalians is highly variable. The tuatara has an average total length of 34.8 and 42.7 centimetres (13.7 and 16.8 in) for females and males respectively.[29] *[Clevosaurus](/source/Clevosaurus) sectumsemper* has an estimated total length of 12 centimetres (4.7 in),[30] while large individuals of the largest known terrestrial sphenodontian, *[Priosphenodon avelasi](/source/Priosphenodon)* reached total lengths of just over 100 centimetres (39 in).[31] The aquatic [pleurosaurs](/source/Pleurosauridae) reached lengths of up to 150 centimetres (59 in).[32]

Most derived rhynchocephalians have the number of presacral vertebrae (the number of vertebrae forward of the [sacrum](/source/Sacrum)) typically around 23-25, though the number is much greater in pleurosaurs, where it reaches up to 57 in some individuals. Seven [cervical vertebrae](/source/Cervical_vertebrae) in the neck may be typical for rhynchocephalians as it is for the tuatara.[33] The tuatara has paired [proatlas](/source/Proatlas) bones between the [atlas](/source/Atlas_(anatomy)) (the first neck vertebra) and the skull, which is widely assumed to be an ancestral feature among reptiles, but which has been lost in squamates.[34] Proatlas bones have not been definitely identified in fossil rhynchocephalians, which may reflect the difficulty in recognising them in fossils rather than genuine absence. Rhynchocephalians typically have amphicoelous [vertebral centra](/source/Vertebral_centra) (both faces are concave) on their presacral vertebrae.[33]

The tuatara has among the highest known ages of sexual maturity among reptiles,[35] at around 9 to 13 years of age,[36] and has a high longevity in comparison to lizards of similar size,[35] with wild individuals likely reaching 70 years, and possibly over 100 years in age.[37] Such a late onset of sexual maturity and longevity may have or not have been typical of extinct rhynchocephalians.[32][38]

## Classification

*[Homeosaurus maximiliani](/source/Homoeosaurus)* from the Late Jurassic of Germany

While the grouping of Rhynchocephalia is well supported, the relationships of many taxa to each other are uncertain, varying substantially between studies.[39] In modern cladistics, the clade Sphenodontia includes all rhynchocephalians other than *[Wirtembergia](/source/Wirtembergia),* as well as *[Gephyrosaurus](/source/Gephyrosaurus)* and other [gephyrosaurids](/source/Gephyrosauridae). Gephyrosaurids have been found as more closely related to squamates in some analyses.[40][20] In 2018, two major clades within Sphenodontia were defined, the [infraorder](/source/Infraorder) **Eusphenodontia** which is defined by the least inclusive [clade](/source/Clade) containing *[Polysphenodon](/source/Polysphenodon), [Clevosaurus hudsoni](/source/Clevosaurus)* and *Sphenodon*, which is supported by the presence of three [synapomorphies](/source/Synapomorphy_and_apomorphy), including the presence of clearly visible wear facets on the teeth of the dentary or maxilla, the [premaxillary](/source/Premaxilla) 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** 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](/source/Posterior_(anatomy)) (hind) edge of the [parietal bone](/source/Parietal_bone) is only slightly curved inward, the [parietal foramen](/source/Pineal_foramen) is found at the same level or forward of the [anterior](/source/Anterior) border of the [supratemporal fenestra](/source/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](/source/Pterygoid_bone) tooth rows are reduced to one or none, and the posterior border of the [ischium](/source/Ischium) is characterised by a distinctive process.[25] 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.[41] In 2022 the extinct clade **Leptorhynchia** was defined, including a variety of neosphenodontians, at least some of which were aquatically adapted, characterised 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.[21] The clade [Opisthodontia](/source/Opisthodontia_(reptile)) has been used for the grouping of all sphenodontians more closely related to *[Priosphenodon](/source/Priosphenodon)* (a member of [Eilenodontinae](/source/Eilenodontinae)) than to *Sphenodon.*[42] Not all studies use this clade, as some studies have found the scope of the clade to be identical to Eilenodontinae.[21]

The family [Sphenodontidae](/source/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.[40] The closest relatives of the tuatara are placed in the clade [Sphenodontinae](/source/Sphenodontinae), which are characterised by a completely closed temporal bar.[19]

The following is a [cladogram](/source/Cladogram) of Rhynchocephalia after DeMar et al. 2022 (based on [maximum parsimony](/source/Maximum_parsimony_(phylogenetics)), note that cladogram collapses into a [polytomy](/source/Polytomy) under [Bayesian analysis](/source/Bayesian_analysis)):[21]

Rhynchocephalia Gephyrosaurus bridensis Sphenodontia Diphydontosaurus avonis Acrosphenodontia Planocephalosaurus robinsonae Rebbanasaurus jaini Godavarisaurus lateefi Theretairus antiquus Eusphenodontia Polysphenodon mulleri Opisthiamimus gregori Clevosauridae Clevosaurus convallis Clevosaurus brasiliensis Clevosaurus hadroprodon Clevosaurus bairdi Clevosaurus hudsoni Clevosaurus cambrica Neosphenodontia Brachyrhinodon taylori Colobops noviportensis Sphenodontidae Sphenodon punctatus (tuatara) Cynosphenodon huizachalensis Sphenovipera jimmysjoyi Kawasphenodon expectatus Kawasphenodon peligrensis Pelecymala robustus Eilenodontinae Fraserosphenodon latidens Opisthias rarus Eilenodon robustus Sphenotitan leyesi Toxolophosaurus cloudi Priosphenodon avelasi Leptorhynchia Homoeosaurus maximiliani Kallimodon pulchellus Sigmala sigmala Vadasaurus herzogi Pleurosauridae Palaeopleurosaurus posidonae Pleurosaurus goldfussi Pleurosaurus ginsburgi Kallimodon cerinensis Sapheosauridae Sapheosaurus thiollierei Ankylosphenodon pachyostosus Oenosaurus muehlheimensis

Cladogram after Simoes et al. 2022 (based on [Bayesian inference](/source/Bayesian_inference) analysis), with better resolved relations of Sphenodontidae and particularly Sphenodontinae:[19]

Sphenodontia †Diphydontosaurus Eusphenodontia †Planocephalosaurus †Clevosaurus Neosphenodontia †Homoeosaurus Pleurosauridae †Palaeopleurosaurus †Derasmosaurus †Pleurosaurus †Leptosaurus †Kallimodon Sapheosauridae †Piocormus †Oenosaurus †Sapheosaurus Sphenodontidae Eilenodontinae †Sphenotitan †Eilenodon †Toxolophosaurus †Priosphenodon Sphenodontinae †Navajosphenodon †Cynosphenodon †Sphenofontis †Kawasphenodon Sphenodon (tuatara)

### Clades and genera

- †*[Wirtembergia](/source/Wirtembergia)*

- †[Gephyrosauridae](/source/Gephyrosauridae)? - †*[Deltadectes](/source/Deltadectes)* - †*[Gephyrosaurus](/source/Gephyrosaurus)* - †*[Penegephyrosaurus](/source/Penegephyrosaurus)*

- †*[Bharatagama](/source/Bharatagama)*?

- **Sphenodontia** Williston 1925 - †*[Agriodontosaurus](/source/Agriodontosaurus)* - †*[Diphydontosaurus](/source/Diphydontosaurus)* - †*[Micromenodon](/source/Micromenodon)* - †*[Paleollanosaurus](/source/Paleollanosaurus)*? - †*[Parvosaurus](/source/Parvosaurus)* - †*[Pelecymala](/source/Pelecymala)* - †*[Whitakersaurus](/source/Whitakersaurus)* - **Acrosphenodontia** Chambi-Trowell et al., 2021 - †*[Godavarisaurus](/source/Godavarisaurus)* - †*[Planocephalosaurus](/source/Planocephalosaurus)* - †*[Rebbanasaurus](/source/Rebbanasaurus)* - †*[Theretairus](/source/Theretairus)* - †*[Sphenocondor](/source/Sphenocondor)* - **Eusphenodontia** Herrera-Flores et al. 2018 - †*[Brachyrhinodon](/source/Brachyrhinodon)* - †*[Colobops](/source/Colobops)*? - †*[Lanceirosphenodon](/source/Lanceirosphenodon)* - †*[Opisthiamimus](/source/Opisthiamimus)* - †*[Polysphenodon](/source/Polysphenodon)* - †[Clevosauridae](/source/Clevosauridae) - †*[Brachyrhinodon](/source/Brachyrhinodon)*? - †*[Clevosaurus](/source/Clevosaurus)* - †*[Polysphenodon](/source/Polysphenodon)*? - †*[Microsphenodon](/source/Microsphenodon)* - †*[Sigmala](/source/Sigmala)* - †*[Trullidens](/source/Trullidens)* - **Neosphenodontia** Herrera-Flores et al. 2018 - †*[Derasmosaurus](/source/Derasmosaurus)* - †*[Lamarquesaurus](/source/Lamarquesaurus)* - †*[Pamizinsaurus](/source/Pamizinsaurus)* - †*[Tingitana](https://en.wikipedia.org/w/index.php?title=Tingitana_anoualae&action=edit&redlink=1)* - †[Opisthodontia](/source/Opisthodontia_(reptiles)) - †*[Alamitosphenos](https://en.wikipedia.org/w/index.php?title=Alamitosphenos&action=edit&redlink=1)* - †[Eilenodontinae](/source/Eilenodontinae) - [Sphenodontidae](/source/Sphenodontidae) - †[Eilenodontinae](/source/Eilenodontinae)? - †*[Eilenodon](/source/Eilenodon)* - †*[Kaikaifilusaurus](/source/Kaikaifilusaurus)* - †*[Patagosphenos](/source/Patagosphenos)* - †*[Priosphenodon](/source/Priosphenodon)* - †*[Sphenotitan](/source/Sphenotitan)* - †*[Toxolophosaurus](/source/Toxolophosaurus)* - †*[Opisthias](/source/Opisthias)*? - †*[Fraserosphenodon](/source/Fraserosphenodon)*? - [Sphenodontinae](/source/Sphenodontinae) - †*[Cynosphenodon](/source/Cynosphenodon)* - †*[Tika](/source/Tika_giacchinoi)* - †*[Sphenofontis](/source/Sphenofontis)* - †*[Navajosphenodon](/source/Navajosphenodon)* - †*[Kawasphenodon](/source/Kawasphenodon)* - †*[Notosphenos](https://en.wikipedia.org/w/index.php?title=Notosphenos&action=edit&redlink=1)* - *[Sphenodon](/source/Sphenodon)* - †**Leptorhynchia** DeMar, Jones & Carrano, 2022 - †*[Homoeosaurus](/source/Homoeosaurus)* - †*[Kallimodon](/source/Kallimodon)* - †*[Leptosaurus](/source/Leptosaurus)* - †*[Vadasaurus](/source/Vadasaurus)* - †*[Ankylosphenodon](/source/Ankylosphenodon)* - †*[Sphenodraco](/source/Sphenodraco)* - †[Sapheosauridae](/source/Sapheosaur) - †*[Oenosaurus](/source/Oenosaurus)* - †*[Piocormus](https://en.wikipedia.org/w/index.php?title=Piocormus&action=edit&redlink=1)* - †*[Sapheosaurus](/source/Sapheosaurus)* - †[Pleurosauridae](/source/Pleurosauridae) - †*[Palaeopleurosaurus](/source/Palaeopleurosaurus)* - †*[Pleurosaurus](/source/Pleurosaurus)* - †?*[Derasmosaurus](/source/Derasmosaurus)* - †?*[Vadasaurus](/source/Vadasaurus)* - †?*[Ankylosphenodon](/source/Ankylosphenodon)*

Gallery of rhynchocephalian skull diversity

		- Skull reconstruction of *[Gephyrosaurus](/source/Gephyrosaurus)* a likely basal rhynchocephalian

		- Reconstruction of the skull of *[Diphydontosaurus](/source/Diphydontosaurus)* a basal member of Sphenodontia

		- Reconstruction of the skulls of *Clevosaurus hudsoni* (A) and *Clevosaurus cambrica* (B)

		- Skull of the basal eusphenodontian *[Opisthiamimus](/source/Opisthiamimus)*

		- Skull of *[Sphenotitan](/source/Sphenotitan)*, an early member of [Eilenodontinae](/source/Eilenodontinae)

		- Reconstruction of the skull of *[Navajosphenodon](/source/Navajosphenodon)*, an early member of [Sphenodontinae](/source/Sphenodontinae)

		- Reconstruction of the skull of the [eilenodontine](/source/Eilenodontinae) *[Priosphenodon](/source/Priosphenodon)*

		- Skull of the neosphenodontian *[Vadasaurus](/source/Vadasaurus)*

		- Skull of *[Pleurosaurus](/source/Pleurosaurus)*

		- Skull diagram of the modern tuatara (*Sphenodon punctatus*)

## Ecology

Skeleton of *[Pleurosaurus](/source/Pleurosaurus),* an aquatically adapted sphenodontian from the Late Jurassic of Germany

The fossil record of rhynchocephalians demonstrates that they were a diverse group that exploited a wide array of ecological niches.[4][27] Early rhynchocephalians possess small ovoid teeth designed for piercing, and were probably [insectivores](/source/Insectivore).[43] Like modern tuatara, extinct members of Sphenodontinae were likely generalists with a carnivorous/insectivorous diet.[44] Amongst the most distinct rhynchocephalians are the [pleurosaurs](/source/Pleurosauridae), 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](/source/Pleurosaurus)* having an elongated triangular skull highly modified from those of other rhynchocephalians. Pleurosaurs are thought to have been [piscivores](/source/Piscivore) (consuming fish).[32] Several other lineages of rhynchocephalians, such as *[Kallimodon](/source/Kallimodon)* and *[Leptosaurus](/source/Leptosaurus)* have been suggested to have had semi-aquatic habits,[45] with fish found as gut contents in one *Kallimodon* specimen.[46]

Skeleton of *[Sphenodraco](/source/Sphenodraco)*, an [arboreal](/source/Arboreal_locomotion), tree-climbing rhynchocephalian from the Late Jurassic of Germany

[Eilenodontines](/source/Eilenodontinae) are thought to have been herbivorous, with batteries of wide teeth with thick [enamel](/source/Tooth_enamel) used to process plant material.[47] The [sapheosaurids](/source/Sapheosauridae), such as *[Oenosaurus](/source/Oenosaurus)* and *[Sapheosaurus](/source/Sapheosaurus)* from the Late Jurassic of Europe possess broad tooth plates unique amongst tetrapods, and are thought to have been [durophagous](/source/Durophagy), with the tooth plates being used to crush hard shelled organisms.[48][40] *[Sphenovipera](/source/Sphenovipera)* from the Jurassic of Mexico has been suggested to have been [venomous](/source/Venomous), based on presence of grooves on two enlarged teeth at the front of the lower jaw[49] though this interpretation has been questioned by other authors.[49] The body of *[Pamizinsaurus](/source/Pamizinsaurus)* from the Early Cretaceous of Mexico was covered in [osteoscutes](/source/Osteoderm), similar to those of [helodermatid](/source/Helodermatidae) lizards like the [Gila monster](/source/Gila_monster), which is unique among known sphenodontians, which probably served to protect it against predators.[50] The limb bone proportions and shape of the hand and foot bones of *[Sphenodraco](/source/Sphenodraco)* from the Late Jurassic of Germany indicate that it was a primarily [arboreal](/source/Arboreal_locomotion) tree climbing animal, unlike the largely terrestrial tuatara. Other extinct rhynchocephalians with relatively long limbs such as *[Navajosphenodon](/source/Navajosphenodon)* and *[Homoeosaurus](/source/Homoeosaurus)* may also have exhibited climbing capabilities.[46]

## Evolutionary history

Skulls of *[Clevosaurus hudsoni](/source/Clevosaurus)* (left) and *[Clevosaurus cambrica](/source/Clevosaurus)* (right)

The timing of when Rhynchocephalia is estimated to have [diverged](/source/Speciation) from Squamata is disputed. Older estimates place the divergence between the [Middle Permian](/source/Guadalupian) and earliest Triassic, around 270 to 252 million years ago,[40] while other authors posit a younger date of around 242 million years ago.[2] The oldest known definitive rhynchocephalian is *[Agriodontosaurus](/source/Agriodontosaurus)* from the [Helsby Sandstone Formation](/source/Helsby_Sandstone_Formation) of [Devon](/source/Devon), UK dating to the upper [Anisian](/source/Anisian) stage of the [Middle Triassic](/source/Middle_Triassic), approximately [244 to 241.5](https://geoltime.github.io/?Ma=244–241.5) million years ago.[1] The next earliest rhynchocephalian is *[Wirtembergia](/source/Wirtembergia)* which is known from the [Erfurt Formation](/source/Erfurt_Formation) near [Vellberg](/source/Vellberg) in Southern Germany, dating to the [Ladinian](/source/Ladinian) stage of the [Middle Triassic](/source/Middle_Triassic), around 238-240 million years old.[20] Rhynchocephalians underwent considerable diversification during the Late Triassic,[4] and reached a worldwide distribution across [Pangaea](/source/Pangaea) by the end of the Triassic, with the [Late Triassic](/source/Late_Triassic)-[Early Jurassic](/source/Early_Jurassic) genus *[Clevosaurus](/source/Clevosaurus)* having 10 species across Asia, Africa, Europe, North and South America.[51] The earliest rhynchocephalians were small animals, but by the Late Triassic the group had evolved a wide range of body sizes.[52] During the Jurassic, rhynchocephalians were the dominant group of small reptiles globally,[53] reaching their apex of morphological diversity during this period, including specialised herbivorous and aquatic forms.[4] The only record of Rhynchocephalians from Asia (excluding the [Indian subcontinent](/source/Indian_subcontinent), which was not part of Asia during the Mesozoic) are indeterminate remains of *Clevosaurus* from the Early Jurassic ([Sinemurian](/source/Sinemurian)) aged [Lufeng Formation](/source/Lufeng_Formation) of [Yunnan](/source/Yunnan), China. Rhynchocephalians are noticeably absent from younger localities in the region, despite the presence of favourable preservation conditions.[54] Rhynchocephalians remained diverse into the Late Jurassic,[55] and were more abundant than lizards during the Late Jurassic in North America.[53]

Rhynchocephalian diversity declined during the [Early Cretaceous](/source/Early_Cretaceous), disappearing from North America and Europe after the end of the epoch,[56] and were absent from North Africa[57] and northern South America[58] by the early [Late Cretaceous](/source/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.[59] They appear to have remained prevalent in southern South America during the Late Cretaceous, where lizards remained rare, with their remains outnumbering terrestrial lizards in this region by a factor of 200.[57] Late Cretaceous South American sphenodontians are represented by both Eilenodontinae and Sphenodontidae (including Sphenodontinae).[60] An indeterminate rhynchocephalian is known from a partial lower jaw of a hatchling from the latest Cretaceous or possibly earliest [Paleocene](/source/Paleocene) [Intertrappean Beds](/source/Intertrappean_Beds), in what was then the isolated landmass of [Insular India](/source/Insular_India), which appears to be an acrosphenodontian, possibly related to *[Godavarisaurus](/source/Godavarisaurus)* from the Jurassic of India.[55] The youngest undoubted remains of rhynchocephalians outside of New Zealand are those of the sphenodontid [*Kawasphenodon peligrensis*](/source/Kawasphenodon) from the early Paleocene ([Danian](/source/Danian)) of [Patagonia](/source/Patagonia) approximately 64-63 million years ago, shortly after the [Cretaceous–Paleogene extinction event](/source/Cretaceous%E2%80%93Paleogene_extinction_event).[61] Indeterminate sphenodontine jaw fragments bearing teeth are known from the early [Miocene](/source/Miocene) (19–16 million years ago) [St Bathans fauna](/source/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](/source/Oceanic_dispersal), and it is thought that they were already present in New Zealand when it separated from [Antarctica](/source/Antarctica) between 80 and 66 million years ago.[59]

## References

1. ^ [***a***](#cite_ref-Markeetal2025_1-0) [***b***](#cite_ref-Markeetal2025_1-1) Marke D, Whiteside DI, Sethapanichsakul T, Coram RA, Fernandez V, Liptak A, et al. (2025-09-10). ["The oldest known lepidosaur and origins of lepidosaur feeding adaptations"](https://www.nature.com/articles/s41586-025-09496-9). *Nature*: 1–10. [doi](/source/Doi_(identifier)):[10.1038/s41586-025-09496-9](https://doi.org/10.1038%2Fs41586-025-09496-9). [ISSN](/source/ISSN_(identifier)) [1476-4687](https://search.worldcat.org/issn/1476-4687). [PMC](/source/PMC_(identifier)) [12629995](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12629995).

1. ^ [***a***](#cite_ref-triassic_origin_2-0) [***b***](#cite_ref-triassic_origin_2-1) Jones ME, Anderson CL, Hipsley CA, Müller J, Evans SE, Schoch RR (September 2013). ["Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara)"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4016551). *[BMC Evolutionary Biology](/source/BMC_Evolutionary_Biology)*. **13** (1): 208. [Bibcode](/source/Bibcode_(identifier)):[2013BMCEE..13..208J](https://ui.adsabs.harvard.edu/abs/2013BMCEE..13..208J). [doi](/source/Doi_(identifier)):[10.1186/1471-2148-13-208](https://doi.org/10.1186%2F1471-2148-13-208). [PMC](/source/PMC_(identifier)) [4016551](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4016551). [PMID](/source/PMID_(identifier)) [24063680](https://pubmed.ncbi.nlm.nih.gov/24063680).

1. **[^](#cite_ref-3)** Reynoso VH (2000). "An unusual aquatic sphenodontian (Reptilia: Diapsida) from the Tlayua Formation (Albian), central Mexico". *[Journal of Paleontology](/source/Journal_of_Paleontology)*. **74** (1): 133–148. [Bibcode](/source/Bibcode_(identifier)):[2000JPal...74..133R](https://ui.adsabs.harvard.edu/abs/2000JPal...74..133R). [doi](/source/Doi_(identifier)):[10.1017/s0022336000031310](https://doi.org/10.1017%2Fs0022336000031310). [S2CID](/source/S2CID_(identifier)) [232346834](https://api.semanticscholar.org/CorpusID:232346834).

1. ^ [***a***](#cite_ref-:6_4-0) [***b***](#cite_ref-:6_4-1) [***c***](#cite_ref-:6_4-2) [***d***](#cite_ref-:6_4-3) Herrera-Flores JA, Stubbs TL, Benton MJ (2017). ["Macroevolutionary patterns in Rhynchocephalia: is the tuatara (Sphenodon punctatus) a living fossil?"](https://doi.org/10.1111%2Fpala.12284). *[Palaeontology](/source/Palaeontology_(journal))*. **60** (3): 319–328. [Bibcode](/source/Bibcode_(identifier)):[2017Palgy..60..319H](https://ui.adsabs.harvard.edu/abs/2017Palgy..60..319H). [doi](/source/Doi_(identifier)):[10.1111/pala.12284](https://doi.org/10.1111%2Fpala.12284). [hdl](/source/Hdl_(identifier)):[1983/940fdc51-30db-47c0-9ac6-97fda3c2ea01](https://hdl.handle.net/1983%2F940fdc51-30db-47c0-9ac6-97fda3c2ea01). [ISSN](/source/ISSN_(identifier)) [1475-4983](https://search.worldcat.org/issn/1475-4983).

1. ^ [***a***](#cite_ref-fraser_5-0) [***b***](#cite_ref-fraser_5-1) Fraser N, Sues HD, eds. (1994). *"Phylogeny" In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods*. [Cambridge University Press](/source/Cambridge_University_Press). p. 25. [ISBN](/source/ISBN_(identifier)) [0-521-45242-2](https://en.wikipedia.org/wiki/Special:BookSources/0-521-45242-2).

1. **[^](#cite_ref-Evansetal01_6-0)** [Evans SE](/source/Susan_E._Evans), Prasad GV, Manhas BK (November 2001). ["Rhynchocephalians (Diapsida: Lepidosauria) from the Jurassic Kota Formation of India"](https://doi.org/10.1111%2Fj.1096-3642.2001.tb00629.x). *[Zoological Journal of the Linnean Society](/source/Zoological_Journal_of_the_Linnean_Society)*. **133** (3): 309–34. [doi](/source/Doi_(identifier)):[10.1111/j.1096-3642.2001.tb00629.x](https://doi.org/10.1111%2Fj.1096-3642.2001.tb00629.x).

1. **[^](#cite_ref-7)** ["Sphenodon"](http://dictionary.reference.com/browse/sphenodon). *Dictionary.com Unabridged (v 1.1)*. [Random House](/source/Random_House), Inc. Retrieved 8 January 2007.

1. **[^](#cite_ref-Sophineta_8-0)** Evans SE, Borsuk-Białynicka M (2009). ["A small lepidosauromorph reptile from the Early Triassic of Poland"](http://palaeontologia.pan.pl/PP65/PP65_179-202.pdf) (PDF). *Paleontologica Polonica*. **65**: 179–202.

1. **[^](#cite_ref-9)** Gauthier, J., Estes, R. & De Queiroz, K. (1988). [A phylogenetic analysis of Lepidosauromorpha.](https://repository.si.edu/bitstream/handle/10088/6458/Gauthier_1988.pdf) In *Phylogenetic Relationships of the Lizard Families* (eds R. Estes and G. Pregill), pp. 15–98. Stanford University Press, Stanford.

1. **[^](#cite_ref-10)** ["Rhynchocephalians"](https://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/rhynchocephalians.html). *[University College London](/source/University_College_London)*. Retrieved 2022-08-09.

1. **[^](#cite_ref-11)** Dendy A (1911). ["VI. On the structure, development and morphological interpretation of the pineal organs and adjacent parts of the brain in the tuatara ( sphenodon punctatus )"](https://doi.org/10.1098%2Frstb.1911.0006). *[Philosophical Transactions of the Royal Society B](/source/Philosophical_Transactions_of_the_Royal_Society_B)*. **201** (274–281): 227–331. [doi](/source/Doi_(identifier)):[10.1098/rstb.1911.0006](https://doi.org/10.1098%2Frstb.1911.0006). [ISSN](/source/ISSN_(identifier)) [0264-3960](https://search.worldcat.org/issn/0264-3960).

1. **[^](#cite_ref-12)** Smith KT, Bhullar BA, Köhler G, Habersetzer J (2 April 2018). ["The only known jawed vertebrate with four eyes and the bauplan of the pineal complex"](https://doi.org/10.1016%2Fj.cub.2018.02.021). *[Current Biology](/source/Current_Biology)*. **28** (7): 1101–1107.e2. [Bibcode](/source/Bibcode_(identifier)):[2018CBio...28E1101S](https://ui.adsabs.harvard.edu/abs/2018CBio...28E1101S). [doi](/source/Doi_(identifier)):[10.1016/j.cub.2018.02.021](https://doi.org/10.1016%2Fj.cub.2018.02.021). [ISSN](/source/ISSN_(identifier)) [0960-9822](https://search.worldcat.org/issn/0960-9822). [PMID](/source/PMID_(identifier)) [29614279](https://pubmed.ncbi.nlm.nih.gov/29614279).

1. ^ [***a***](#cite_ref-:17_13-0) [***b***](#cite_ref-:17_13-1) Benoit J, Abdala F, Manger P, Rubidge B (2016). ["The sixth sense in mammalians forerunners: variability of the parietal foramen and the evolution of the pineal eye in South African Permo-Triassic eutheriodont therapsids"](http://www.app.pan.pl/article/item/app002192015.html). *Acta Palaeontologica Polonica*. [doi](/source/Doi_(identifier)):[10.4202/app.00219.2015](https://doi.org/10.4202%2Fapp.00219.2015).

1. **[^](#cite_ref-14)** Paulina-Carabajal A, Jiménez-Huidobro P, Triviño LN, Stanley EL, Zaher H, Daza JD (2023), Dozo MT, Paulina-Carabajal A, Macrini TE, Walsh S (eds.), ["A Look in to the Neurocranium of Living and Extinct Lepidosauria"](https://link.springer.com/10.1007/978-3-031-13983-3_5), *Paleoneurology of Amniotes*, Cham: Springer International Publishing, pp. 123–177, [doi](/source/Doi_(identifier)):[10.1007/978-3-031-13983-3_5](https://doi.org/10.1007%2F978-3-031-13983-3_5), [ISBN](/source/ISBN_(identifier)) [978-3-031-13982-6](https://en.wikipedia.org/wiki/Special:BookSources/978-3-031-13982-6), retrieved 2023-12-08{{[citation](https://en.wikipedia.org/wiki/Template:Citation)}}: CS1 maint: work parameter with ISBN ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_work_parameter_with_ISBN))

1. **[^](#cite_ref-15)** Jones ME, Cree A (December 2012). ["Tuatara"](https://linkinghub.elsevier.com/retrieve/pii/S0960982212013036). *Current Biology*. **22** (23): R986–R987. [doi](/source/Doi_(identifier)):[10.1016/j.cub.2012.10.049](https://doi.org/10.1016%2Fj.cub.2012.10.049).

1. **[^](#cite_ref-:2_16-0)** Vitt LJ, Caldwell JP (2014). "Chapter 20: Rhynchocephalians (Sphenodontids)". *Herpetology*. Elsevier. pp. 553–554. [doi](/source/Doi_(identifier)):[10.1016/b978-0-12-386919-7.00020-4](https://doi.org/10.1016%2Fb978-0-12-386919-7.00020-4). [ISBN](/source/ISBN_(identifier)) [978-0-12-386919-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-386919-7).

1. **[^](#cite_ref-17)** Sanger TJ, Gredler ML, Cohn MJ (October 2015). ["Resurrecting embryos of the tuatara, Sphenodon punctatus, to resolve vertebrate phallus evolution"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4650183). *[Biology Letters](/source/Biology_Letters)*. **11** (10) 20150694. [doi](/source/Doi_(identifier)):[10.1098/rsbl.2015.0694](https://doi.org/10.1098%2Frsbl.2015.0694). [PMC](/source/PMC_(identifier)) [4650183](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4650183). [PMID](/source/PMID_(identifier)) [26510679](https://pubmed.ncbi.nlm.nih.gov/26510679).

1. **[^](#cite_ref-18)** Evans SE, Jones ME (2010). "The Origin, Early History and Diversification of Lepidosauromorph Reptiles". *New Aspects of Mesozoic Biodiversity*. Lecture Notes in Earth Sciences. Vol. 132. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 27–44. [Bibcode](/source/Bibcode_(identifier)):[2010LNES..132...27E](https://ui.adsabs.harvard.edu/abs/2010LNES..132...27E). [doi](/source/Doi_(identifier)):[10.1007/978-3-642-10311-7_2](https://doi.org/10.1007%2F978-3-642-10311-7_2). [ISBN](/source/ISBN_(identifier)) [978-3-642-10310-0](https://en.wikipedia.org/wiki/Special:BookSources/978-3-642-10310-0).

1. ^ [***a***](#cite_ref-:8_19-0) [***b***](#cite_ref-:8_19-1) [***c***](#cite_ref-:8_19-2) Simões TR, Kinney-Broderick G, Pierce SE (March 2022). ["An exceptionally preserved Sphenodon-like sphenodontian reveals deep time conservation of the tuatara skeleton and ontogeny"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8894340). *[Communications Biology](/source/Communications_Biology)*. **5** (1): 195. [doi](/source/Doi_(identifier)):[10.1038/s42003-022-03144-y](https://doi.org/10.1038%2Fs42003-022-03144-y). [PMC](/source/PMC_(identifier)) [8894340](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8894340). [PMID](/source/PMID_(identifier)) [35241764](https://pubmed.ncbi.nlm.nih.gov/35241764).

1. ^ [***a***](#cite_ref-:9_20-0) [***b***](#cite_ref-:9_20-1) [***c***](#cite_ref-:9_20-2) [***d***](#cite_ref-:9_20-3) [***e***](#cite_ref-:9_20-4) Sues HD, Schoch RR (2023-11-07). ["The oldest known rhynchocephalian reptile from the Middle Triassic (Ladinian) of Germany and its phylogenetic position among Lepidosauromorpha"](https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25339). *The Anatomical Record*. **307** (4): 776–790. [doi](/source/Doi_(identifier)):[10.1002/ar.25339](https://doi.org/10.1002%2Far.25339). [ISSN](/source/ISSN_(identifier)) [1932-8486](https://search.worldcat.org/issn/1932-8486). [PMID](/source/PMID_(identifier)) [37937325](https://pubmed.ncbi.nlm.nih.gov/37937325).

1. ^ [***a***](#cite_ref-:14_21-0) [***b***](#cite_ref-:14_21-1) [***c***](#cite_ref-:14_21-2) [***d***](#cite_ref-:14_21-3) DeMar DG, Jones ME, Carrano MT (2022-12-31). ["A nearly complete skeleton of a new eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the evolution and diversity of Rhynchocephalia (Reptilia: Lepidosauria)"](https://www.tandfonline.com/doi/full/10.1080/14772019.2022.2093139). *Journal of Systematic Palaeontology*. **20** (1): 1–64. [doi](/source/Doi_(identifier)):[10.1080/14772019.2022.2093139](https://doi.org/10.1080%2F14772019.2022.2093139). [hdl](/source/Hdl_(identifier)):[2440/136608](https://hdl.handle.net/2440%2F136608). [ISSN](/source/ISSN_(identifier)) [1477-2019](https://search.worldcat.org/issn/1477-2019). [S2CID](/source/S2CID_(identifier)) [252325953](https://api.semanticscholar.org/CorpusID:252325953).

1. ^ [***a***](#cite_ref-:18_22-0) [***b***](#cite_ref-:18_22-1) Ford DP, Evans SE, Choiniere JN, Fernandez V, Benson RB (2021-08-25). ["A reassessment of the enigmatic diapsid Paliguana whitei and the early history of Lepidosauromorpha"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8385343). *Proceedings of the Royal Society B: Biological Sciences*. **288** (1957) 20211084. [doi](/source/Doi_(identifier)):[10.1098/rspb.2021.1084](https://doi.org/10.1098%2Frspb.2021.1084). [ISSN](/source/ISSN_(identifier)) [0962-8452](https://search.worldcat.org/issn/0962-8452). [PMC](/source/PMC_(identifier)) [8385343](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8385343). [PMID](/source/PMID_(identifier)) [34428965](https://pubmed.ncbi.nlm.nih.gov/34428965).

1. **[^](#cite_ref-23)** Evans SE (2016), Clack JA, Fay RR, Popper AN (eds.), ["The Lepidosaurian Ear: Variations on a Theme"](http://link.springer.com/10.1007/978-3-319-46661-3_9), *Evolution of the Vertebrate Ear*, Springer Handbook of Auditory Research, vol. 59, Cham: Springer International Publishing, pp. 245–284, [doi](/source/Doi_(identifier)):[10.1007/978-3-319-46661-3_9](https://doi.org/10.1007%2F978-3-319-46661-3_9), [ISBN](/source/ISBN_(identifier)) [978-3-319-46659-0](https://en.wikipedia.org/wiki/Special:BookSources/978-3-319-46659-0), retrieved 2024-01-08{{[citation](https://en.wikipedia.org/wiki/Template:Citation)}}: CS1 maint: work parameter with ISBN ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_work_parameter_with_ISBN))

1. ^ [***a***](#cite_ref-:15_24-0) [***b***](#cite_ref-:15_24-1) [***c***](#cite_ref-:15_24-2) Jenkins KM, Jones ME, Zikmund T, Boyde A, Daza JD (September 2017). ["A Review of Tooth Implantation Among Rhynchocephalians (Lepidosauria)"](https://www.researchgate.net/publication/318718114_A_Review_of_Tooth_Implantation_Among_Rhynchocephalians_Lepidosauria). *[Journal of Herpetology](/source/Journal_of_Herpetology)*. **51** (3): 300–306. [doi](/source/Doi_(identifier)):[10.1670/16-146](https://doi.org/10.1670%2F16-146). [ISSN](/source/ISSN_(identifier)) [0022-1511](https://search.worldcat.org/issn/0022-1511). [S2CID](/source/S2CID_(identifier)) [90519352](https://api.semanticscholar.org/CorpusID:90519352).

1. ^ [***a***](#cite_ref-:16_25-0) [***b***](#cite_ref-:16_25-1) Herrera-Flores JA, Stubbs TL, Elsler A, Benton MJ (2018-04-06). ["Taxonomic reassessment of Clevosaurus latidens Fraser, 1993 (Lepidosauria, Rhynchocephalia) and rhynchocephalian phylogeny based on parsimony and Bayesian inference"](https://doi.org/10.1017%2Fjpa.2017.136). *[Journal of Paleontology](/source/Journal_of_Paleontology)*. **92** (4): 734–742. [Bibcode](/source/Bibcode_(identifier)):[2018JPal...92..734H](https://ui.adsabs.harvard.edu/abs/2018JPal...92..734H). [doi](/source/Doi_(identifier)):[10.1017/jpa.2017.136](https://doi.org/10.1017%2Fjpa.2017.136). [hdl](/source/Hdl_(identifier)):[1983/59126b60-16d8-46d2-b657-954693a39d4e](https://hdl.handle.net/1983%2F59126b60-16d8-46d2-b657-954693a39d4e).

1. ^ [***a***](#cite_ref-:13_26-0) [***b***](#cite_ref-:13_26-1) Matsumoto R, Evans SE (January 2017). ["The palatal dentition of tetrapods and its functional significance"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5192890). *[Journal of Anatomy](/source/Journal_of_Anatomy)*. **230** (1): 47–65. [doi](/source/Doi_(identifier)):[10.1111/joa.12534](https://doi.org/10.1111%2Fjoa.12534). [PMC](/source/PMC_(identifier)) [5192890](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5192890). [PMID](/source/PMID_(identifier)) [27542892](https://pubmed.ncbi.nlm.nih.gov/27542892).

1. ^ [***a***](#cite_ref-:7_27-0) [***b***](#cite_ref-:7_27-1) Jones ME (August 2008). ["Skull shape and feeding strategy in Sphenodon and other Rhynchocephalia (Diapsida: Lepidosauria)"](https://doi.org/10.1002%2Fjmor.10634). *Journal of Morphology*. **269** (8): 945–966. [doi](/source/Doi_(identifier)):[10.1002/jmor.10634](https://doi.org/10.1002%2Fjmor.10634). [PMID](/source/PMID_(identifier)) [18512698](https://pubmed.ncbi.nlm.nih.gov/18512698).

1. **[^](#cite_ref-28)** Jones ME, O'higgins P, Fagan MJ, Evans SE, Curtis N (July 2012). ["Shearing mechanics and the influence of a flexible symphysis during oral food processing in Sphenodon (Lepidosauria: Rhynchocephalia)"](https://doi.org/10.1002%2Far.22487). *Anatomical Record*. **295** (7): 1075–1091. [doi](/source/Doi_(identifier)):[10.1002/ar.22487](https://doi.org/10.1002%2Far.22487). [PMID](/source/PMID_(identifier)) [22644955](https://pubmed.ncbi.nlm.nih.gov/22644955).

1. **[^](#cite_ref-29)** Herrel A, Moore JA, Bredeweg EM, Nelson NJ (2010-05-19). ["Sexual dimorphism, body size, bite force and male mating success in tuatara: SEXUAL DIMORPHISM IN TUATARA"](https://doi.org/10.1111%2Fj.1095-8312.2010.01433.x). *Biological Journal of the Linnean Society*. **100** (2): 287–292. [doi](/source/Doi_(identifier)):[10.1111/j.1095-8312.2010.01433.x](https://doi.org/10.1111%2Fj.1095-8312.2010.01433.x).

1. **[^](#cite_ref-30)** Keeble E, Whiteside DI, Benton MJ (April 2018). ["The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures, South Wales, UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)"](https://linkinghub.elsevier.com/retrieve/pii/S0016787817301529). *Proceedings of the Geologists' Association*. **129** (2): 99–119. [Bibcode](/source/Bibcode_(identifier)):[2018PrGA..129...99K](https://ui.adsabs.harvard.edu/abs/2018PrGA..129...99K). [doi](/source/Doi_(identifier)):[10.1016/j.pgeola.2017.11.001](https://doi.org/10.1016%2Fj.pgeola.2017.11.001). [hdl](/source/Hdl_(identifier)):[1983/5afdc677-3ea0-4519-813d-6052ef8370ec](https://hdl.handle.net/1983%2F5afdc677-3ea0-4519-813d-6052ef8370ec).

1. **[^](#cite_ref-Apesteguia_and_Novas_2003_31-0)** Apesteguía S, Novas FE (9 October 2003). "Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana". *Nature*. **425** (6958): 609–612. [Bibcode](/source/Bibcode_(identifier)):[2003Natur.425..609A](https://ui.adsabs.harvard.edu/abs/2003Natur.425..609A). [doi](/source/Doi_(identifier)):[10.1038/nature01995](https://doi.org/10.1038%2Fnature01995). [PMID](/source/PMID_(identifier)) [14534584](https://pubmed.ncbi.nlm.nih.gov/14534584). [S2CID](/source/S2CID_(identifier)) [4425130](https://api.semanticscholar.org/CorpusID:4425130).

1. ^ [***a***](#cite_ref-:11_32-0) [***b***](#cite_ref-:11_32-1) [***c***](#cite_ref-:11_32-2) Klein N, Scheyer TM (February 2017). "Microanatomy and life history in Palaeopleurosaurus (Rhynchocephalia: Pleurosauridae) from the Early Jurassic of Germany". *Die Naturwissenschaften*. **104** (1–2): 4. [Bibcode](/source/Bibcode_(identifier)):[2017SciNa.104....4K](https://ui.adsabs.harvard.edu/abs/2017SciNa.104....4K). [doi](/source/Doi_(identifier)):[10.1007/s00114-016-1427-3](https://doi.org/10.1007%2Fs00114-016-1427-3). [PMID](/source/PMID_(identifier)) [28005148](https://pubmed.ncbi.nlm.nih.gov/28005148). [S2CID](/source/S2CID_(identifier)) [27133670](https://api.semanticscholar.org/CorpusID:27133670).

1. ^ [***a***](#cite_ref-:22_33-0) [***b***](#cite_ref-:22_33-1) Beccari V, Jones ME, Villa A, Martino R, Regnault S, Glaw F, et al. (2026-04-01). ["The axial skeleton of the tuatara (Rhynchocephalia: Sphenodon ): insights on intraspecific variability, ontogeny, sexual dimorphism, and remarks on fossil taxa"](https://academic.oup.com/zoolinnean/article/doi/10.1093/zoolinnean/zlaf135/8570147). *Zoological Journal of the Linnean Society*. **206** (4). [doi](/source/Doi_(identifier)):[10.1093/zoolinnean/zlaf135](https://doi.org/10.1093%2Fzoolinnean%2Fzlaf135). [ISSN](/source/ISSN_(identifier)) [0024-4082](https://search.worldcat.org/issn/0024-4082).

1. **[^](#cite_ref-Korneisel2025_34-0)** Korneisel DE, Maddin HC (2025-07-22). ["Review of the tetrapod skull–neck boundary: implications for the evolution of the atlas–axis complex"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12586291). *Biological Reviews*. [doi](/source/Doi_(identifier)):[10.1111/brv.70053](https://doi.org/10.1111%2Fbrv.70053). [PMC](/source/PMC_(identifier)) [12586291](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12586291).

1. ^ [***a***](#cite_ref-:19_35-0) [***b***](#cite_ref-:19_35-1) Hallmann K, Griebeler EM (June 2018). ["An exploration of differences in the scaling of life history traits with body mass within reptiles and between amniotes"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010814). *Ecology and Evolution*. **8** (11): 5480–5494. [Bibcode](/source/Bibcode_(identifier)):[2018EcoEv...8.5480H](https://ui.adsabs.harvard.edu/abs/2018EcoEv...8.5480H). [doi](/source/Doi_(identifier)):[10.1002/ece3.4069](https://doi.org/10.1002%2Fece3.4069). [ISSN](/source/ISSN_(identifier)) [2045-7758](https://search.worldcat.org/issn/2045-7758). [PMC](/source/PMC_(identifier)) [6010814](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010814). [PMID](/source/PMID_(identifier)) [29938067](https://pubmed.ncbi.nlm.nih.gov/29938067).

1. **[^](#cite_ref-36)** Newman DG (July 1988). "Evidence of predation on a young tuatara, *Sphenodon punctatus*, by kiore, *Rattus exulans*, on Lady Alice Island". *New Zealand Journal of Zoology*. **15** (3): 443–446. [doi](/source/Doi_(identifier)):[10.1080/03014223.1988.10422973](https://doi.org/10.1080%2F03014223.1988.10422973). [ISSN](/source/ISSN_(identifier)) [0301-4223](https://search.worldcat.org/issn/0301-4223).

1. **[^](#cite_ref-37)** Nelson NJ, Keall SN, Pledger S, Daugherty CH (May 2002). ["Male-biased sex ratio in a small tuatara population"](https://onlinelibrary.wiley.com/doi/10.1046/j.1365-2699.2002.00712.x). *Journal of Biogeography*. **29** (5–6): 633–640. [Bibcode](/source/Bibcode_(identifier)):[2002JBiog..29..633N](https://ui.adsabs.harvard.edu/abs/2002JBiog..29..633N). [doi](/source/Doi_(identifier)):[10.1046/j.1365-2699.2002.00712.x](https://doi.org/10.1046%2Fj.1365-2699.2002.00712.x). [ISSN](/source/ISSN_(identifier)) [0305-0270](https://search.worldcat.org/issn/0305-0270).

1. **[^](#cite_ref-38)** Cavasín S, Cerda I, Apesteguia S (2024). ["Bone microstructure of Priosphenodon avelasi (Rhynchocephalia: Sphenodontia): paleobiological implications"](https://www.app.pan.pl/article/item/app010712023.html). *Acta Palaeontologica Polonica*. **69**. [doi](/source/Doi_(identifier)):[10.4202/app.01071.2023](https://doi.org/10.4202%2Fapp.01071.2023).

1. **[^](#cite_ref-39)** Romo de Vivar PR, Martinelli AG, Schmaltz Hsiou A, Soares MB (2020-07-02). "A New Rhynchocephalian from the Late Triassic of Southern Brazil Enhances Eusphenodontian Diversity". *[Journal of Systematic Palaeontology](/source/Journal_of_Systematic_Palaeontology)*. **18** (13): 1103–1126. [Bibcode](/source/Bibcode_(identifier)):[2020JSPal..18.1103R](https://ui.adsabs.harvard.edu/abs/2020JSPal..18.1103R). [doi](/source/Doi_(identifier)):[10.1080/14772019.2020.1732488](https://doi.org/10.1080%2F14772019.2020.1732488). [ISSN](/source/ISSN_(identifier)) [1477-2019](https://search.worldcat.org/issn/1477-2019). [S2CID](/source/S2CID_(identifier)) [216226211](https://api.semanticscholar.org/CorpusID:216226211).

1. ^ [***a***](#cite_ref-:3_40-0) [***b***](#cite_ref-:3_40-1) [***c***](#cite_ref-:3_40-2) [***d***](#cite_ref-:3_40-3) Simões TR, Caldwell MW, Pierce SE (December 2020). ["Sphenodontian phylogeny and the impact of model choice in Bayesian morphological clock estimates of divergence times and evolutionary rates"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720557). *[BMC Biology](/source/BMC_Biology)*. **18** (1): 191. [doi](/source/Doi_(identifier)):[10.1186/s12915-020-00901-5](https://doi.org/10.1186%2Fs12915-020-00901-5). [PMC](/source/PMC_(identifier)) [7720557](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720557). [PMID](/source/PMID_(identifier)) [33287835](https://pubmed.ncbi.nlm.nih.gov/33287835).

1. **[^](#cite_ref-41)** Chambi-Trowell SA, Martinelli AG, Whiteside DI, Vivar PR, Soares MB, Schultz CL, et al. (2021-06-03). ["The diversity of Triassic South American sphenodontians: a new basal form, clevosaurs, and a revision of rhynchocephalian phylogeny"](https://www.tandfonline.com/doi/full/10.1080/14772019.2021.1976292). *[Journal of Systematic Palaeontology](/source/Journal_of_Systematic_Palaeontology)*. **19** (11): 787–820. [Bibcode](/source/Bibcode_(identifier)):[2021JSPal..19..787C](https://ui.adsabs.harvard.edu/abs/2021JSPal..19..787C). [doi](/source/Doi_(identifier)):[10.1080/14772019.2021.1976292](https://doi.org/10.1080%2F14772019.2021.1976292). [hdl](/source/Hdl_(identifier)):[1983/af14affc-a26e-426b-83ca-e1833e355882](https://hdl.handle.net/1983%2Faf14affc-a26e-426b-83ca-e1833e355882). [ISSN](/source/ISSN_(identifier)) [1477-2019](https://search.worldcat.org/issn/1477-2019). [S2CID](/source/S2CID_(identifier)) [240487298](https://api.semanticscholar.org/CorpusID:240487298).

1. **[^](#cite_ref-42)** Apesteguía S, Novas FE (2003-10-09). ["Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana"](https://www.nature.com/articles/nature01995). *Nature*. **425** (6958): 609–612. [Bibcode](/source/Bibcode_(identifier)):[2003Natur.425..609A](https://ui.adsabs.harvard.edu/abs/2003Natur.425..609A). [doi](/source/Doi_(identifier)):[10.1038/nature01995](https://doi.org/10.1038%2Fnature01995). [ISSN](/source/ISSN_(identifier)) [0028-0836](https://search.worldcat.org/issn/0028-0836). [PMID](/source/PMID_(identifier)) [14534584](https://pubmed.ncbi.nlm.nih.gov/14534584).

1. **[^](#cite_ref-43)** Jones ME (2009). Koppe T, Meyer G, Alt KW, Brook A (eds.). "Dentary Tooth Shape in Sphenodon and Its Fossil Relatives (Diapsida: Lepidosauria: Rhynchocephalia)". *[Frontiers of Oral Biology](/source/Frontiers_of_Oral_Biology)*. **13**. Basel: Karger: 9–15. [doi](/source/Doi_(identifier)):[10.1159/000242382](https://doi.org/10.1159%2F000242382). [ISBN](/source/ISBN_(identifier)) [978-3-8055-9229-1](https://en.wikipedia.org/wiki/Special:BookSources/978-3-8055-9229-1). [PMID](/source/PMID_(identifier)) [19828962](https://pubmed.ncbi.nlm.nih.gov/19828962).

1. **[^](#cite_ref-44)** Villa A, Montie R, Röper M, Rothgaenger M, Rauhut OW (2021-05-03). ["Sphenofontis velserae gen. et sp. nov., a new rhynchocephalian from the Late Jurassic of Brunn (Solnhofen Archipelago, southern Germany)"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8101455). *PeerJ*. **9** e11363. [doi](/source/Doi_(identifier)):[10.7717/peerj.11363](https://doi.org/10.7717%2Fpeerj.11363). [ISSN](/source/ISSN_(identifier)) [2167-8359](https://search.worldcat.org/issn/2167-8359). [PMC](/source/PMC_(identifier)) [8101455](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8101455). [PMID](/source/PMID_(identifier)) [33987027](https://pubmed.ncbi.nlm.nih.gov/33987027).

1. **[^](#cite_ref-:10_45-0)** Bever GS, Norell MA (November 2017). ["A new rhynchocephalian (Reptilia: Lepidosauria) from the Late Jurassic of Solnhofen (Germany) and the origin of the marine Pleurosauridae"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717629). *Royal Society Open Science*. **4** (11) 170570. [doi](/source/Doi_(identifier)):[10.1098/rsos.170570](https://doi.org/10.1098%2Frsos.170570). [PMC](/source/PMC_(identifier)) [5717629](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717629). [PMID](/source/PMID_(identifier)) [29291055](https://pubmed.ncbi.nlm.nih.gov/29291055).

1. ^ [***a***](#cite_ref-Sphenodraco_46-0) [***b***](#cite_ref-Sphenodraco_46-1) Beccari V, Guillaume AR, Jones ME, Villa A, Cooper N, Regnault S, et al. (2025-07-01). ["An arboreal rhynchocephalian from the Late Jurassic of Germany, and the importance of the appendicular skeleton for ecomorphology in lepidosaurs"](https://doi.org/10.1093%2Fzoolinnean%2Fzlaf073). *[Zoological Journal of the Linnean Society](/source/Zoological_Journal_of_the_Linnean_Society)*. **204** (3) zlaf073. [doi](/source/Doi_(identifier)):[10.1093/zoolinnean/zlaf073](https://doi.org/10.1093%2Fzoolinnean%2Fzlaf073). [hdl](/source/Hdl_(identifier)):[10362/186782](https://hdl.handle.net/10362%2F186782). [ISSN](/source/ISSN_(identifier)) [0024-4082](https://search.worldcat.org/issn/0024-4082).

1. **[^](#cite_ref-47)** Jones ME, Lucas PW, Tucker AS, Watson AP, Sertich JJ, Foster JR, et al. (June 2018). ["Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6030635). *Journal of the Royal Society, Interface*. **15** (143) 20180039. [doi](/source/Doi_(identifier)):[10.1098/rsif.2018.0039](https://doi.org/10.1098%2Frsif.2018.0039). [PMC](/source/PMC_(identifier)) [6030635](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6030635). [PMID](/source/PMID_(identifier)) [29899156](https://pubmed.ncbi.nlm.nih.gov/29899156).

1. **[^](#cite_ref-Rauhut2012_48-0)** Rauhut OW, Heyng AM, López-Arbarello A, Hecker A (2012). Farke AA (ed.). ["A new rhynchocephalian from the late jurassic of Germany with a dentition that is unique amongst tetrapods"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485277). *[PLOS ONE](/source/PLOS_ONE)*. **7** (10) e46839. [Bibcode](/source/Bibcode_(identifier)):[2012PLoSO...746839R](https://ui.adsabs.harvard.edu/abs/2012PLoSO...746839R). [doi](/source/Doi_(identifier)):[10.1371/journal.pone.0046839](https://doi.org/10.1371%2Fjournal.pone.0046839). [PMC](/source/PMC_(identifier)) [3485277](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485277). [PMID](/source/PMID_(identifier)) [23118861](https://pubmed.ncbi.nlm.nih.gov/23118861).

1. ^ [***a***](#cite_ref-Folinsbee_547–551_49-0) [***b***](#cite_ref-Folinsbee_547–551_49-1) Folinsbee KE, Müller J, Reisz RR (2007-06-12). ["Canine grooves: morphology, function, and relevance to venom"](http://www.tandfonline.com/doi/abs/10.1671/0272-4634%282007%2927%5B547%3ACGMFAR%5D2.0.CO%3B2). *Journal of Vertebrate Paleontology*. **27** (2): 547–551. [doi](/source/Doi_(identifier)):[10.1671/0272-4634(2007)27\[547:CGMFAR\]2.0.CO;2](https://doi.org/10.1671%2F0272-4634%282007%2927%5B547%3ACGMFAR%5D2.0.CO%3B2). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634).

1. **[^](#cite_ref-:02_50-0)** Reynoso VH (1997-04-16). ["A "beaded" sphenodontian (Diapsida: Lepidosauria) from the Early Cretaceous of central Mexico"](https://www.researchgate.net/publication/254313967). *Journal of Vertebrate Paleontology*. **17** (1): 52–59. [Bibcode](/source/Bibcode_(identifier)):[1997JVPal..17...52R](https://ui.adsabs.harvard.edu/abs/1997JVPal..17...52R). [doi](/source/Doi_(identifier)):[10.1080/02724634.1997.10010953](https://doi.org/10.1080%2F02724634.1997.10010953). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634).

1. **[^](#cite_ref-51)** Chambi-Trowell SA, Whiteside DI, Benton MJ, Rayfield EJ (November 2020). Lautenschlager S (ed.). "Biomechanical properties of the jaws of two species of Clevosaurus and a reanalysis of rhynchocephalian dentary morphospace". *[Palaeontology](/source/Palaeontology_(journal))*. **63** (6): 919–939. [Bibcode](/source/Bibcode_(identifier)):[2020Palgy..63..919C](https://ui.adsabs.harvard.edu/abs/2020Palgy..63..919C). [doi](/source/Doi_(identifier)):[10.1111/pala.12493](https://doi.org/10.1111%2Fpala.12493). [S2CID](/source/S2CID_(identifier)) [220902843](https://api.semanticscholar.org/CorpusID:220902843).

1. **[^](#cite_ref-52)** Herrera-Flores JA, Elsler A, Stubbs TL, Benton MJ (2021). ["Slow and fast evolutionary rates in the history of lepidosaurs"](https://doi.org/10.1111%2Fpala.12579). *[Palaeontology](/source/Palaeontology_(journal))*. **65**. [doi](/source/Doi_(identifier)):[10.1111/pala.12579](https://doi.org/10.1111%2Fpala.12579). [ISSN](/source/ISSN_(identifier)) [1475-4983](https://search.worldcat.org/issn/1475-4983). [S2CID](/source/S2CID_(identifier)) [244019684](https://api.semanticscholar.org/CorpusID:244019684).

1. ^ [***a***](#cite_ref-:20_53-0) [***b***](#cite_ref-:20_53-1) Brownstein CD, Meyer DL, Fabbri M, Bhullar BA, Gauthier JA (2022-11-29). ["Evolutionary origins of the prolonged extant squamate radiation"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9708687). *Nature Communications*. **13** (1): 7087. [Bibcode](/source/Bibcode_(identifier)):[2022NatCo..13.7087B](https://ui.adsabs.harvard.edu/abs/2022NatCo..13.7087B). [doi](/source/Doi_(identifier)):[10.1038/s41467-022-34217-5](https://doi.org/10.1038%2Fs41467-022-34217-5). [ISSN](/source/ISSN_(identifier)) [2041-1723](https://search.worldcat.org/issn/2041-1723). [PMC](/source/PMC_(identifier)) [9708687](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9708687). [PMID](/source/PMID_(identifier)) [36446761](https://pubmed.ncbi.nlm.nih.gov/36446761).

1. **[^](#cite_ref-:12_54-0)** Jones ME (2006). ["The Early Jurassic clevosaurs from China (Diapsida: Lepidosauria)"](https://www.researchgate.net/publication/230865919). *New Mexico Museum of Natural History and Science Bulletin*. **37**: 548–562.

1. ^ [***a***](#cite_ref-:21_55-0) [***b***](#cite_ref-:21_55-1) Anantharaman S, DeMar DG, Sivakumar R, Dassarma DC, Wilson Mantilla GP, Wilson Mantilla JA (2022-06-30). ["First rhynchocephalian (Reptilia, Lepidosauria) from the Cretaceous–Paleogene of India"](https://doi.org/10.1080%2F02724634.2022.2118059). *Journal of Vertebrate Paleontology*. **42** (1) e2118059. [Bibcode](/source/Bibcode_(identifier)):[2022JVPal..42E8059A](https://ui.adsabs.harvard.edu/abs/2022JVPal..42E8059A). [doi](/source/Doi_(identifier)):[10.1080/02724634.2022.2118059](https://doi.org/10.1080%2F02724634.2022.2118059). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634). [S2CID](/source/S2CID_(identifier)) [252558728](https://api.semanticscholar.org/CorpusID:252558728).

1. **[^](#cite_ref-:0_56-0)** Cleary TJ, Benson RB, Evans SE, Barrett PM (March 2018). ["Lepidosaurian diversity in the Mesozoic-Palaeogene: the potential roles of sampling biases and environmental drivers"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882712). *Royal Society Open Science*. **5** (3) 171830. [Bibcode](/source/Bibcode_(identifier)):[2018RSOS....571830C](https://ui.adsabs.harvard.edu/abs/2018RSOS....571830C). [doi](/source/Doi_(identifier)):[10.1098/rsos.171830](https://doi.org/10.1098%2Frsos.171830). [PMC](/source/PMC_(identifier)) [5882712](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882712). [PMID](/source/PMID_(identifier)) [29657788](https://pubmed.ncbi.nlm.nih.gov/29657788).

1. ^ [***a***](#cite_ref-:5_57-0) [***b***](#cite_ref-:5_57-1) Apesteguía S, Daza JD, Simões TR, Rage JC (September 2016). ["The first iguanian lizard from the Mesozoic of Africa"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5043327). *Royal Society Open Science*. **3** (9) 160462. [Bibcode](/source/Bibcode_(identifier)):[2016RSOS....360462A](https://ui.adsabs.harvard.edu/abs/2016RSOS....360462A). [doi](/source/Doi_(identifier)):[10.1098/rsos.160462](https://doi.org/10.1098%2Frsos.160462). [PMC](/source/PMC_(identifier)) [5043327](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5043327). [PMID](/source/PMID_(identifier)) [27703708](https://pubmed.ncbi.nlm.nih.gov/27703708).

1. **[^](#cite_ref-58)** Simões TR, Wilner E, Caldwell MW, Weinschütz LC, Kellner AW (August 2015). ["A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4560825). *[Nature Communications](/source/Nature_Communications)*. **6** (1): 8149. [Bibcode](/source/Bibcode_(identifier)):[2015NatCo...6.8149S](https://ui.adsabs.harvard.edu/abs/2015NatCo...6.8149S). [doi](/source/Doi_(identifier)):[10.1038/ncomms9149](https://doi.org/10.1038%2Fncomms9149). [PMC](/source/PMC_(identifier)) [4560825](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4560825). [PMID](/source/PMID_(identifier)) [26306778](https://pubmed.ncbi.nlm.nih.gov/26306778).

1. ^ [***a***](#cite_ref-:4_59-0) [***b***](#cite_ref-:4_59-1) Jones ME, Tennyson AJ, Worthy JP, Evans SE, Worthy TH (April 2009). ["A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon)"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660973). *Proceedings of the Royal Society B: Biological Sciences*. **276** (1660): 1385–90. [doi](/source/Doi_(identifier)):[10.1098/rspb.2008.1785](https://doi.org/10.1098%2Frspb.2008.1785). [PMC](/source/PMC_(identifier)) [2660973](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660973). [PMID](/source/PMID_(identifier)) [19203920](https://pubmed.ncbi.nlm.nih.gov/19203920).

1. **[^](#cite_ref-60)** Agnolín FL, Aranciaga Rolando AM, Chimento NR, Novas FE (October 2023). ["New small reptile remains from the Late Cretaceous of Patagonia increase morphological diversity of sphenodontids (Lepidosauria)"](https://linkinghub.elsevier.com/retrieve/pii/S0016787823000809). *Proceedings of the Geologists' Association*. **135**: 36–44. [doi](/source/Doi_(identifier)):[10.1016/j.pgeola.2023.09.007](https://doi.org/10.1016%2Fj.pgeola.2023.09.007).

1. **[^](#cite_ref-:1_61-0)** Apesteguía S, Gómez RO, Rougier GW (October 2014). ["The youngest South American rhynchocephalian, a survivor of the K/Pg extinction"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4150314). *Proceedings of the Royal Society B: Biological Sciences*. **281** (1792) 20140811. [doi](/source/Doi_(identifier)):[10.1098/rspb.2014.0811](https://doi.org/10.1098%2Frspb.2014.0811). [PMC](/source/PMC_(identifier)) [4150314](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4150314). [PMID](/source/PMID_(identifier)) [25143041](https://pubmed.ncbi.nlm.nih.gov/25143041).

## Further reading

- Apesteguia S, Rougier GW (2007). ["A Late Campanian Sphenodontid Maxilla from Northern Patagonia"](http://digitallibrary.amnh.org/bitstream/handle/2246/5874//v3/dspace/updateIngest/pdfs/N3581.pdf?sequence=1&isAllowed=y) (PDF). *[American Museum Novitates](/source/American_Museum_Novitates)* (3581): 1–12. [doi](/source/Doi_(identifier)):[10.1206/0003-0082(2007)3581\[1:ALCSMF\]2.0.CO;2](https://doi.org/10.1206%2F0003-0082%282007%293581%5B1%3AALCSMF%5D2.0.CO%3B2). Retrieved 2019-03-30.

- Daugherty CH, Cree A, Hay JM, Thompson MB (1990). "Neglected taxonomy and continuing extinctions of tuatara (*Sphenodon*)". *[Nature](/source/Nature_(journal))*. **347** (6289): 177–179. [Bibcode](/source/Bibcode_(identifier)):[1990Natur.347..177D](https://ui.adsabs.harvard.edu/abs/1990Natur.347..177D). [doi](/source/Doi_(identifier)):[10.1038/347177a0](https://doi.org/10.1038%2F347177a0). [S2CID](/source/S2CID_(identifier)) [4342765](https://api.semanticscholar.org/CorpusID:4342765).

- Evans SE (November 2003). ["At the feet of the dinosaurs: the early history and radiation of lizards"](http://doc.rero.ch/record/16165/files/PAL_E3367.pdf) (PDF). *Biological Reviews of the Cambridge Philosophical Society*. **78** (4): 513–51. [doi](/source/Doi_(identifier)):[10.1017/S1464793103006134](https://doi.org/10.1017%2FS1464793103006134). [PMID](/source/PMID_(identifier)) [14700390](https://pubmed.ncbi.nlm.nih.gov/14700390). [S2CID](/source/S2CID_(identifier)) [4845536](https://api.semanticscholar.org/CorpusID:4845536).

- Gemmell NJ, Rutherford K, Prost S, Tollis M, Winter D, Macey JR, et al. (August 2020). ["The tuatara genome reveals ancient features of amniote evolution"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116210). *[Nature](/source/Nature_(journal))*. **584** (7821): 403–409. [doi](/source/Doi_(identifier)):[10.1038/s41586-020-2561-9](https://doi.org/10.1038%2Fs41586-020-2561-9). [PMC](/source/PMC_(identifier)) [7116210](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116210). [PMID](/source/PMID_(identifier)) [32760000](https://pubmed.ncbi.nlm.nih.gov/32760000).

## External links

- Media related to [Sphenodontia](https://commons.wikimedia.org/wiki/Category:Sphenodontia) at Wikimedia Commons

- Data related to [Rhynchocephalia](https://species.wikimedia.org/wiki/Rhynchocephalia) at Wikispecies

v t e Rhynchocephalia Kingdom: Animalia Phylum: Chordata Class: Reptilia Superorder: Lepidosauria Sauropsida see Sauropsida Lepidosauromorpha see Lepidosauromorpha Rhynchocephalia see below↓ Rhynchocephalia Rhynchocephalia †Wirtembergia †Gephyrosauridae? Gephyrosaurus Penegephyrosaurus Deltadectes Sphenodontia †Diphydontosaurus †Godavarisaurus †Micromenodon †Parvosaurus †Pelecymala †Rebbanasaurus †Sphenocondor Incertae sedis †Paleollanosaurus †Whitakersaurus Acrosphenodontia †Planocephalosaurus †Godavarisaurus? Eusphenodontia †Lanceirosphenodon †Microsphenodon †Opisthiamimus †Polysphenodon †Clevosauridae Brachyrhinodon Clevosaurus Polysphenodon? Neosphenodontia †Colobops? †Homoeosaurus †Lanceirosphenodon? †Pamizinsaurus †Rebbanasaurus? †Sphenocondor? †Sphenodraco †Theretairus †Zapatadon †Kallimodon †Leptosaurus †Sapheosauridae Piocormus Sapheosaurus Oenosaurus "Eupropalinal sphenodonts" †Lamarquesaurus †Sigmala †Tingitana †Vadasaurus †Pleurosauridae? Palaeopleurosaurus Pleurosaurus Tingitana? Vadasaurus? Sphenodontidae †Ankylosphenodon †Cynosphenodon †Derasmosaurus †Kawasphenodon? †Navajosphenodon †Notosphenos †Pamizinsaurus? Sphenodon †Sphenofontis †Sphenovipera? †Theretairus? †Tika †Zapatadon? †Opisthodontia Alamitosphenos Fraserosphenodon Kawasphenodon? Opisthias Pelecymala? Trullidens Pleurosauridae? Sapheosauridae? Eilenodontinae Eilenodon Kaikaifilusaurus Patagosphenos Priosphenodon Sphenotitan? Toxolophosaurus

v t e Major extant reptile clades Lepidosauria Rhynchocephalia (tuataras) Squamata (snakes and lizards) Archelosauria Testudines (turtles) Archosauria Aves (birds) Crocodilia (crocodiles, alligators, caimans, and relatives) Outline of reptiles Reptiles portal Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata

v t e Extant chordate classes Kingdom Animalia Clade Bilateria Superphylum Deuterostomia Cephalochordata Leptocardii (lancelets) Olfactores Tunicata (Urochordata) Appendicularia (larvaceans) Acopa Stolidobranchia¹ Thaliacea (pyrosomes, salps, doliolids) Enterogona Phlebobranchia¹ Aplousobranchia¹ Vertebrata Cyclostomata Myxini (hagfish) Hyperoartia (lampreys) Gnathostomata (jawed vertebrates) Chondrichthyes (cartilaginous fish: sharks, rays, chimaeras) Euteleostomi (bony vertebrates) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths)² Rhipidistia Dipnoi (lungfish)² Tetrapoda Lissamphibia (modern amphibians: frogs, salamanders, caecilians) Amniota Mammalia (mammals) Sauria Lepidosauria Rhynchocephalia (tuatara)³ Squamata (scaled reptiles: snakes, lizards, worm lizards)³ Archelosauria Testudines (turtles)³ Archosauria Crocodilia (crocodilians)³ Aves (birds) ¹orders of class Ascidiacea (sea squirts) ²classes of clade Sarcopterygii (lobe-finned fish and descendants) ³orders of traditional class Reptilia (reptiles) italics denote paraphyletic groups

Taxon identifiers Rhynchocephalia Wikidata: Q15099738 Wikispecies: Rhynchocephalia ADW: Rhynchocephalia BOLD: 757339 EoL: 1736 GBIF: 703 iNaturalist: 26162 IRMNG: 12254 ITIS: 173860 NZOR: 6e3ccfba-0389-4235-ad8e-558e96c6d70a Open Tree of Life: 35876 Paleobiology Database: 54194

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Adapted from the Wikipedia article [Rhynchocephalia](https://en.wikipedia.org/wiki/Rhynchocephalia) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rhynchocephalia?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.