Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. 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.
Planocephalosaurus is an extinct genus of basal rhynchocephalian. Fossils of the genus are primarily known from fissure fill deposits from the Late Triassic of southwest Britain, with fragmentary remains possibly belonging to the genus also known from the Late Triassic of Texas.
Clevosaurus is an extinct genus of rhynchocephalian reptile from the Late Triassic and the Early Jurassic periods. Species of Clevosaurus were widespread across Pangaea, and have been found on all continents except Australia and Antarctica. Five species of Clevosaurus have been found in ancient fissure fill deposits in south-west England and Wales, alongside other sphenodontians, early mammals and dinosaurs. In regards to its Pangaean distribution, C. hadroprodon is the oldest record of a sphenodontian from Gondwana, though its affinity to Clevosaurus has been questioned.
Scleroglossa is a group of lizards that includes geckos, autarchoglossans, and amphisbaenians. Scleroglossa is supported by phylogenetic analyses that use morphological features. According to most morphological analyses, Scleroglossa is the sister group of the clade Iguania, which includes iguanas, chameleons, agamids, and New World lizards. Together, Scleroglossa and Iguania make up the crown group Squamata, the smallest evolutionary grouping to include all living lizards and snakes.
Theretairus is a Late Jurassic genus of sphenodont reptile from the Morrison Formation of western North America, present in stratigraphic zones 5 and 6.
Diphydontosaurus is an extinct genus of small rhynchocephalian reptile from the Late Triassic of Europe. It is the most primitive known member of Sphenodontia.
Gephyrosaurus is a genus of early rhynchocephalian first described and named in 1980 by Susan E. Evans. They are distantly related to the extant Sphenodon with which they shared a number of skeletal features including a large tooth row along the side of the palatine bone and posterior process of the dentary bone. The type species, G. bridensis, lived during Early Jurassic in Wales, UK. Whiteside & Duffin (2017) described the second species, G. evansae, known from a partial maxilla recovered from Late Triassic (Rhaetian) fissure fills in Carboniferous Limestone in Somerset. Gephyrosaurus, other potential gephyrosaurids and Wirtembergia are the only rhynchocephalians to lie outside Sphenodontia in modern definitions of the group, and have been found to be more closely related to squamates in some phylogenetic analyses.
Manidens is an extinct genus of heterodontosaurid dinosaur from the Early Jurassic of Patagonia. It is a sister taxon of the closely related Pegomastax from South Africa. Fossils have been found in the Cañadón Asfalto Formation in Chubut Province, Argentina, dating to the Toarcian.
Pegomastax is a genus of heterodontosaurid dinosaur that lived during the Early Jurassic of South Africa. The only known specimen was discovered in a 1966-1967 expedition in Transkei District of Cape Province, but wasn't described until 2012 when Paul Sereno named it as the new taxon Pegomastax africana. The genus name is derived from the Greek for "strong jaw", and the species name describes the provenance of Africa; it was originally spelled africanus, was corrected to africana to align with the gender of the genus name.
Barbaturex is an extinct genus of giant herbivorous iguanian lizards from Pondaung Formation, the Eocene of Myanmar. It is represented by a single species, Barbaturex morrisoni, which is known from several partial dentaries and a fused pair of frontals, two bones that form part of the top of the skull. Based on the size of these bones, Barbaturex morrisoni is estimated to have been about 1 metre (3.3 ft) from snout to vent, and possibly up to 6 feet (1.8 m) including the tail. Barbaturex morrisoni was named after The Doors frontman Jim Morrison, a play on his epithet "The Lizard King". The genus's name is a portmanteau of the Latin words Barbatus and rex, meaning "bearded king", in reference to ridges along the mandible and the lizard's large size.
Uquiasaurus is an extinct genus of iguanian lizards represented by the type species Uquiasaurus heptanodonta from the Late Pliocene of Argentina. Uquiasaurus was first described in 2012 on the basis of isolated snout and jaw bones within the Uquía Formation, the namesake of the genus. These bones were preserved in a midden of predatory bird pellets and are part of a microvertebrate assemblage that includes the bones of rodents, marsupials, frogs, birds, and other lizards, one of the few to document the mixing of North and South American faunas during the Great American Interchange. Phylogenetic analysis indicates that Uquiasaurus is part of a clade of iguanians that includes the living families Liolaemidae, Leiocephalidae, and Tropiduridae. The status of U. heptanodonta as a valid taxon was contested by Scanferla & Díaz-Fernández (2023), who reinterpreted the type series of this species as a fossil bone assemblage composed by more than one species of Liolaemus. Below is a cladogram from Daza et al. (2012) showing its phylogenetic relationships:
Heterodontagama is an extinct genus of iguanian lizard from the Early Eocene of India. It belongs to the extinct family Priscagamidae, which is otherwise only known from the Late Cretaceous of Mongolia. The type species Heterodontagama borsukae was named in 2013 from several isolated upper and lower jaws found in an exposure of the Cambay Shale in an open-pit coal mine in Gujarat.
Pleurodontagama is an extinct genus of iguanian lizard from the Late Cretaceous of Mongolia. The type species, Pleurodontagama aenigmatodes, was named in 1984 on the basis of a mostly complete skull and isolated lower jaw from a fossil locality called Khermeen Tsav. It has a wide skull with a flat snout, large eye sockets, and small bumps on the surfaces of the bones. Pleurodontagama was initially classified in the family Priscagamidae, which is usually grouped in a large clade of iguanians called Acrodonta, members of which are characterized by an "acrodont" dentition in which the teeth grow from the margins of the jaws. However, Pleurodontagama is unusual in that it has a sub-pleurodont dentition, meaning that some of its teeth grow from the inner surfaces of the jaw. There is also evidence to suggest that its teeth may have been continuously replaced throughout life, as opposed to the permanent teeth of acrodontans. Pleurodontagama may have been a transitional form between the derived acrodont type and the pleurodont type inferred for the ancestors of Acrodonta.
Phrynosomimus is an extinct genus of iguanian lizard from the Late Cretaceous of Mongolia belonging to the extinct family Priscagamidae. The type species Phrynosomimus asper was named in 1996. Fossils have been found in the Barun Goyot and Djadochta formations and include several complete skulls. Phrynosomimus has a short, triangular skull with bony spikes projecting from the back, stemming from the squamosal and parietal bones. These spikes give it a similar appearance to the modern horned lizard Phrynosoma and inspire its name, which means "Phrynosoma mimic." Like other priscagamids it has an acrodont dentition, meaning that its teeth grow from the margins of the jaws rather than their inner surfaces, as is the case for the pleurodont dentitions of most lizards.
Gueragama is an extinct genus of iguanian lizard from the Cretaceous of Brazil. It belongs to a group of iguanians called Acrodonta, whose living members include chameleons and agamids and are currently restricted to the Old World. Gueragama is the only acrodont known from South America, providing evidence that the group once ranged across much of Gondwana and only became restricted to the Old World after the supercontinent broke apart. The type species, Gueragama sulamericana, was named in 2015 on the basis of an isolated lower jaw from Goio-Erê Formation in the Bauru Basin, which was deposited in a desert environment. Although description shows age of Formation at Turonian to Campanian, later study proposes age around Aptian to Albian instead. Unlike modern acrodontans, whose teeth implant on the margins of the jaws, Gueragama has teeth that implant along the inner surface of the lower jaw, a feature common in most non-acrodontan lizards and characteristic of the second major group of iguanians, Pleurodonta. The non-acrodont dentition of Gueragama is evidence of its basal position within Acrodonta, and is shared with the taxon of Late Cretaceous acrodontan relatives, the family Priscagamidae.
Acrodonta are a subclade of iguanian squamates consisting almost entirely of Old World taxa. Extant representation include the families Chamaeleonidae (chameleons) and Agamidae, with at least over 500 species described. A fossil genus, Gueragama, was found in Brazil, making it the only known American representative of the group.
Whitakersaurus is a genus of sphenodontid rhynchocephalian reptile dated to be late Triassic in age and is from the Ghost Ranch fossil quarry in New Mexico, USA. It is named after the discoverer of the Ghost Ranch quarry, George O. Whitaker. The fossil was described in 2007.
Magnuviator is a genus of extinct iguanomorph lizard from the Late Cretaceous of Montana, US. It contains one species, M. ovimonsensis, described in 2017 by DeMar et al. from two specimens that were discovered in the Egg Mountain nesting site. Magnuviator is closest related to the Asian Saichangurvel and Temujinia, which form the group Temujiniidae. Unlike other members of the Iguanomorpha, however, Magnuviator bears a distinct articulating notch on its tibia for the ankle bones, which has traditionally been considered a characteristic of non-iguanomorph lizards. The morphology of its teeth suggests that its diet would have mainly consisted of wasps, like the modern phyrnosomatid iguanians Callisaurus and Urosaurus, although it also shows some adaptations to herbivory.
Opisthodontia is a proposed clade of sphenodontian reptiles, uniting Opisthias from the Late Jurassic-earliest Cretaceous of Europe and North America with the Eilenodontinae, a group of herbivorous sphenodontians known from the Late Triassic to Late Cretaceous.
Fraxinisaura is an extinct genus of basal lepidosauromorph reptile known from the Middle Triassic of Germany. The only known species is Fraxinisaura rozynekae. It possessed an elongated snout, unique features of the teeth, and an ilium which was intermediate in orientation between sphenodontians and squamates. Based on characteristics of the maxilla, it is considered a close relative of Marmoretta from the Middle Jurassic of the United Kingdom, resolving a ghost lineage between that genus and other Triassic basal lepidosauromorphs.
