The Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes lizards and snakes. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.
Squamata is the largest order of reptiles, comprising lizards and snakes. With over 11,500 species, it is also the second-largest order of extant (living) vertebrates, after the perciform fish. Squamates are distinguished by their skins, which bear horny scales or shields, and must periodically engage in molting. They also possess movable quadrate bones, making possible movement of the upper jaw relative to the neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamates are the most variably sized living reptiles, ranging from the 16 mm (0.63 in) dwarf gecko to the 6.5 m (21 ft) reticulated python. The now-extinct mosasaurs reached lengths over 14 m (46 ft).
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.
Lepidosauromorpha is a group of reptiles comprising all diapsids closer to lizards than to archosaurs. The only living sub-group is the Lepidosauria, which contains two subdivisions, Squamata, which contains lizards and snakes, and Rhynchocephalia, the only extant species of which is the tuatara.
Eolacertilia is an extinct clade of lepidosauriform diapsid reptiles known from the Late Permian to the Late Triassic. It is uncertain as to whether they are a natural group and it has been suggested that they form a "waste basket" taxon. Currently, the only members of the group are Paliguana and Kuehneosauridae. Other genera were transferred to basal groups within Diapsida, Archosauromorpha.
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.
Eileanchelys is an extinct genus of primitive turtle from the Middle Jurassic (Bathonian) period some 164 million years ago of Britain. Only one species is recorded, Eileanchelys waldmani. It is the best-represented turtle from the Middle Jurassic, because of the amount of specimens that can be assigned to it. The turtle is also one of the oldest turtles ever found to be aquatic, and might represent a milestone in turtle evolution.
Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America.
Gephyrosaurus is an extinct genus of lepidosaurian reptile known from the Late Triassic to Early Jurassic of the United Kingdom. It is generally considered to be one of the most primitive members of the clade Rhynchocephalia.
Godavarisaurus is an extinct genus of sphenodontian reptile from the Early-Middle Jurassic Kota Formation of Andhra Pradesh, India. It is known from jaw fragments. It was a small sphenodontian, with the skull estimated to be less than 2 centimetres (0.79 in) long. It is generally considered to be a relatively basal sphenodontian that lies outside Eusphenodontia.
Sophineta is an extinct genus of basal lepidosauromorph reptile known from the Early Triassic of Małopolska Province, southern Poland. It contains a single species, Sophineta cracoviensis.
Susan Elizabeth Evans is a British palaeontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters.
Megachirella is an extinct genus of lepidosaur, possibly a stem-squamate that lived about 240 million years ago during the Middle Triassic and contains only one known species, Megachirella wachtleri. It is known from a partial skeleton discovered in the Dolomites of Northern Italy and was described in 2003.
The Kilmaluag Formation is a Middle Jurassic geologic formation in Scotland. It was formerly known as the Ostracod Limestone for preserving an abundance of fossil freshwater/low salinity ostracods. Gastropods, bivalves, trace fossil burrows, and vertebrate fossil remains have also been recorded from the formation. Vertebrate fossils include fish, crocodylomorphs, mammals, small reptiles, amphibians, theropod and sauropod dinosaurs and pterosaurs.
Rebbanasaurus is an extinct sphenodontian reptile known from remains found in the Early-Middle Jurassic Kota Formation of India. The type specimen is a partial jawbone which has acrodont teeth, with other known remains including fragments of the premaxilla, maxilla, and palatine. It was relatively small, with a skull estimated at 1.5–2.5 centimetres (0.59–0.98 in) long. It is generally considered to be a relatively basal sphenodontian that lies outside Eusphenodontia.
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.
Taytalura is an extinct genus of lepidosauromorph reptile from the Late Triassic of Argentina. It contains a single species, Taytalura alcoberi, which is based on a well-preserved skull from the fossiliferous Ischigualasto Formation. As a lepidosauromorph, Taytalura is a distant relative of modern lepidosaurs such as sphenodontians and squamates. Taytalura did not belong to any group of modern lepidosaurs, since it bears unique features, such as unfused bones in the skull roof and teeth which all sit loosely in a deep groove without sockets. Regardless, Micro-CT scanning reveals features of the skull previously only seen in rhynchocephalians. This suggests that the ancestral condition of the skull in lepidosaurs was more similar to sphenodonts than to squamates.
Palaeagama is an extinct genus of neodiapsid reptile from the Late Permian or Early Triassic of South Africa. It is based on an articulated skeleton which was probably found in the Early Triassic Lystrosaurus Assemblage Zone, or potentially the Late Permian Daptocephalus Assemblage Zone. Despite the completeness of the specimen, Palaeagama is considered as a "wildcard" taxon of uncertain affinities due to poor preservation. It was originally considered an "eosuchian", and later reinterpreted as a lizard ancestor closely related to Paliguana and Saurosternon. Modern studies generally consider it an indeterminate neodiapsid, though a few phylogenetic analyses tentatively support a position at the base of Lepidosauromorpha.
Michael Waldman is a British palaeontologist known for his work on fossil fish, mammals, and reptiles. He also discovered the globally important fossil site of Cladach a'Ghlinne, near Elgol on the Isle of Skye, Scotland. This site exposes the Kilmaluag Formation and provides a valuable record of Middle Jurassic ecosystems. During the 1970s he visited the site several times with fellow palaeontologist Robert Savage. The fossil turtle Eileanchelys waldmani was named after Michael in recognition of his notable contribution to palaeontology.
Saurosternon is an extinct genus of neodiapsid reptile from the Late Permian of South Africa. It is based on a partial skeleton split between two slabs of sandstone from the Daptocephalus Assemblage Zone. Saurosternon was one of the earliest small lizard-like reptiles to be discovered in Permian deposits of the Karoo Supergroup, preceding later discoveries such as Paliguana, Youngina, Palaeagama, and Lacertulus. The skeleton is mostly complete, though missing the head. Most of the original bone had decayed away by the time the fossil was discovered, leaving perfect molds in the sandstone slabs. What little bone remained was removed with acid by museum preparators, and the specimen was cast with latex to reconstruct the original bone shape.
