Reptile Classification

Reptiles are animals that rely on the environment to heat and cool them, making them ectothermic. They are also covered in scales or a bony external plate called scutes.


The class Reptilia contains the following major groups: Testudines (turtles, terrapins and tortoises), Squamata (lizards and snakes) and Crocodilia (crocodiles, gavials, caimans, alligators and tuatara). This classification uses skull morphology and other anatomical characteristics to distinguish reptiles from birds and mammals.


Reptiles are cold-blooded vertebrates that evolved from amphibians about 320 million years ago. They are classified in the phylum Chordata, and include snakes, lizards, turtles and alligators. They are the first animals to adapt to living on land, and have many adaptations including camouflage, biting and hissing.

They are characterized by a skull with a solid roof, no temporal openings, and limbs that may be clawed or paddle-like. Their body is encased in a shell (carapace or plastron) of dermal bone plates. They are the most diverse group of reptiles, and include all types of lizards and snakes, as well as crocodiles, alligators, caimans and gila monsters. 레오파드게코

Classification of Reptiles is based on their Skull Structure and Temporal Openings. Reptiles are divided into four subclasses: Euryapsida, Lepidosauria, Squamata and Testudines. Euryapsida consists of primitive Reptiles, which have a single skull opening on either side bounded above by the postorbital and squamosal bones. It is further divided into two super orders: Archosauria and Lepidosauria.


In a strict cladistic sense, “reptile” refers to all anapsid and diapsid animals (that is, lizards, snakes, crocodiles, turtles, and endothermic birds). However, because of the unique characteristics that they possess, most paleontologists c 레오파드게코 onsider birds as distinct from traditional reptiles.

Diapsids are distinguished from more primitive reptiles by the presence of two holes, called temporal fenestrae, in their skulls. These allow the attachment of muscles used for jaw movement. These skull openings were first developed about 300 million years ago during the Carboniferous period. The living diapsids are extremely diverse and include lizards, snakes, tuatara, and all crocodiles.

The earliest known diapsids are lepidosauromorphs, a clade that includes modern lizards and snakes and extinct dinosaurs. Another clade, the archosauromorphs, first appeared in the late Permian and contains extinct and modern crocodiles, alligators, and pterosaurs. Birds are now considered to be part of the archosauromorph clade, although many scientists believe that they belong to an outlying clade, which would include terrestrial sphenodontidans such as Gephyrosaurus. These sphenodontidans shared a similar body form with the tuatara, but had triangular teeth that gave them a shearing bite.


The chelonians (formerly Chelonia) are the turtles, tortoises, and terrapins of the reptilian order Testudines. These animals have large dome-shaped shells, short legs, and are found in warm wetlands and oceans around the world. They are omnivores and eat fruits, veggies, and meat. They also tend to sleep a lot! According to Ocala veterinarians, a sleeping reptile is characterized by periods of immobility, eyes closed, lowered respiratory and cardiac activity, and lower behavioral responsiveness to stimuli.

The chelonians are divisible into two groups: the Euereta and the Trionychoidea. The Euereta is composed of two genuses, Gymnopus and Cryptopus, that live in fresh waters. The genus Chelonia contains the green sea turtle (Chelonia mydas) and four coastal species. The genus Trionychoidea contains land tortoises. The latter have horn-rimmed jaws and front legs that assist in the tearing of food. Phylogenetic analyses place them close to pareiasaurs but further away from the Archosaurornophidae, which includes snakes and lizards. They do not have temporal openings in the skull and use anaerobic respiration. Their bones are covered with a horny layer over a bony carapace and plastron, which makes them slow-moving and heavy.


Crocodiles are in the sub-super group of Archosauriformes (dinosaurs and their descendants). Their skulls have flattened sides, and the internal nostrils are lowered into depressions on the anterior part of the pterygoids. Their skin, which is shed like a coat, is covered with non-overlapping scales that contain the protein keratin (the same substance that forms hooves, feathers, claws, and hair in other tetrapods). Crocodylians also have a secondary bony palate that separates the nasal passage from the mouth opening to the choanae, allowing them to eat and breathe simultaneously.

Small prey is deftly manipulated with the jaws for immediate swallowing; larger prey is dismembered by holding it firmly and spinning its body axis several times to tear it apart. They are able to detect and track the movements of their prey by special sense organs embedded in their head, body, legs, and tail.

There are four living genera of crocodilians: Crocodylus, Alligatoridae, Gavialidae, and Tomistoma. Crocodylidae species are found across Africa, Asia, and South America. Gavialidae includes the single species gharial and is restricted to India and surrounding countries. Tomistoma is a monotypic genus that was discovered in the Philippines.


The tuatara (Sphenodon punctatus) is the sole survivor of an ancient reptile order that thrived during most of the Triassic period 250 million years ago. It is a keystone species of New Zealand and an iconic and treasured taonga, or gift, for Maori.

These enigmatic terrestrial vertebrates are capable of consuming large prey items and can grow to more than 80 cm from head to tail, with a spiny crest running along their backs. They have a distinctive tooth arrangement with a single row of teeth in the lower jaw fitting between two rows in the upper jaw. Tuataras also have a third eye on the top of their heads, which is not used for vision and is thought to function as an organ of hearing in low-intensity light.

Although tuataras are classified as lizards, they have features more common with birds, turtles and crocodiles and should be included in the taxonomic order Rhynchocephalia rather than in the reptile order Sphenodontia. Molecular analyses have shown that tuataras are closer to squamates, the most closely related living reptiles, than they are to modern snakes. They have a number of aspects of biology that are unique within, or atypical of, reptiles, including temperature-dependent sex determination, low basal metabolic rates and longevity2.