Lepidosauromorpha (in PhyloCode known as ''Pan-Lepidosauria'') is a group of

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s comprising all diapsids closer to

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s than to

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

s (which include

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

s and birds). The only living sub-group is the Lepidosauria, which contains two subdivisions, Squamata, which contains

lizards Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia althou ...

and

snakes Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joi ...

, and

Rhynchocephalia Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse g ...

, the only extant species of which is the tuatara. Lepidosauromorphs are distinguishable from

archosauromorphs Archosauromorpha ( Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, lizard ...

(reptiles closer to archosaurs) by their primitive sprawling gait (allowing for the same sinusoidal trunk and tail movement seen in fish), the sliding "joint" between the coracoids and the sternum (for a longer stride), and their pleurodont dentition. In contrast, Archosauromorphs possess a

parasagittal The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divid ...

gait, a reduction in their dermal girdle, a reduction and/or loss of the sternum, and a more thecodont dentition. Living lepidosauromorphs have retained an ectothermic (" cold blooded") metabolism, unlike the ancestral condition in archosauromorphs. While some putative stem-lepidosauromorphs like ''

Palaeagama ''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 potenti ...

'' are known from the Late Permian, the oldest definitive lepidosauromorphs, ''

Sophineta ''Sophineta'' is an extinct genus of basal lepidosauromorph reptile known from the Early Triassic (late Olenekian age) of Małopolska Province, southern Poland. It contains a single species, ''Sophineta cracoviensis''. Discovery ''Sophineta'' ...

'' and '' Paliguana'', are known from the Early Triassic. ''

Taytalura ''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 late Carnian Ischigualasto Formation. Alt ...

'' from the early Late Triassic of Argentina is the most complete fossil of an early lepidosauromorph and is one of the few fossils robustly inferred as an early evolving lepidosauromorph. The Kuehneosauridae, a family of reptiles with elongated ribs which allowed them to glide akin to living gliding lizards have been historically typically considered early lepidosauromorphs. However, several recent studies have been found them in other positions within Sauria, including Archosauromorpha. Almost all non-lepidosaurian lepidosauromorphs became extinct by the end of the Triassic, the with the latest non lepidosaur-lepidosauromorphs being '' Marmoretta'' from the Middle Jurassic of Britain and an indeterminate form from the Middle Jurassic

Moskvoretskaya Formation The Moskvoretskaya Formation is a Middle Jurassic (Bathonian stage) geologic formation in the European part of Russia. It consists of continental claystones, siltstones and sandstones deposited in karstified segments of underlying Middle Carboni ...

of Russia, which appear to be closely related to ''

Fraxinisaura ''Fraxinisaura'' is an extinct genus of basal (phylogenetics), 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 ...

'' from the Middle Triassic of Germany. Other studies have recovered ''Marmoretta'' as a stem-squamate.

References

Tetrapod unranked clades Early Triassic reptiles Extant Early Triassic first appearances Olenekian first appearances {{Reptile-stub

See also

References