Reptile Classification


Reptile classification is a way of grouping different types of reptiles. It identifies how they are related to each other and their evolutionary history. These animals are ectothermic, have scales, a closed cloaca for excretion and reproduction, paired limbs with five toes, and lungs rather than gills for respiration.


The genus Reptile is used for all living or extinct vertebrates that belong to the subclass Sauropsida, which includes all modern and most extinct lizards, snakes, turtles, and crocodiles.

Class Reptilia

Class Reptilia contains all the living species of lizards, snakes, turtles and crocodiles. They are tetrapod vertebrates with scaled skin and are classified as amniotes (animals whose embryos are aided and protected by multiple membranes, either carried inside or laid outside).

Most reptiles are oviparous, laying eggs that must be kept cool to prevent water loss. However, a number of squamate reptiles can give live birth and are known as viviparous or ovoviviparous. Most viviparous reptiles use a forked tongue to sense smell, and the tongue is believed to have high sensory capabilities. In some viviparous species, males may use scent to locate females and complete fertilization internally.

Historically, the term reptile has been used to refer to all the members of the class Sauropsida, including lizards and birds. In recent times, phylogenetic studies have challenged this arrangement and led to a number of changes in the classification of reptiles. Some lizards have been moved to the class Theropsida, while others have been assigned to the class Mammalida.

Class Reptilia is now divided into four orders, with each order being further subdivided into families and genera. These include the Squamata, which includes lizards and snakes; Testudines, which includes turtles; and Crocodylia, which includes alligators and crocodiles. Currently, the tuatara, a primitive reptile, is classified as a viviparous squamate.

Sub-class Sauropsida

A broad group of modern and 파충류샵 extinct lizards, snakes, turtles, and crocodiles, as well as mammals and their extinct relatives. Originally defined at the turn of the twentieth century by Edwin Stephen Goodrich, who used a number of features (especially the anatomy of the heart and blood vessels) to distinguish these two major evolutionary lineages, Sauropsida (“Lizard Faces”) and Theropsida (“Beast Faces”).

This subclassification was based on the positioning of temporal fenestrae — holes in the skull behind the eyes that allow reptiles to reduce stress on their head bones while biting. The first branch to split from this clade was the Anapsida, whose members did not develop the temporal fenestrae. The other branch was the Diapsida, which did develop these holes in their skulls. This group branched further to produce the Lepidosaurs (modern snakes, lizards and tuataras) and the Archosaurs (birds under Reptiles, but also crocodiles and non-bird dinosaurs).

The last branch to split from this clade was Synapsida, containing the modern mammals and their extinct relatives. This group branched further to produce both the short neck pliosaurs, such as Kronosaurus qeenslandicus from the Early Cretaceous of Queensland, and the long neck pliosaurs, like Hypuronector from the Late Permian of Argentina. Due to the difficulty of assigning these groups to their correct phylogenetic positions, this subdivision has been less popular since the advent of phylogenetic classifications.

Sub-class Synapsida

During the Permian period, four-limbed vertebrates that could not swim or fly evolved into a group known as the synapsids. A synapsid is distinguished by the presence of a hole, called the temporal fenestra, in the skull behind each eye. A synapsid’s skull was also more massive than that of a reptile, and it evolved to support the weight of the head. These changes enabled synapsids to move faster and breathe more efficiently than reptiles. During the late Permian, a synapsid genus called Dimetrodon emerged with some of the features that characterize mammals today. These characteristics included an erect gait, allowing the limbs to articulate at the shoulders and hips, a smaller brain, and specialized teeth. These synapsids are sometimes referred to as mammal-like reptiles or mammal precursors, but cladistic classifications do not consider them to be reptiles at all.

In modern cladistic classifications, the traditional Linnean classification has been replaced by a newer phylogenetic tree. The class Reptilia now consists of all amniotes sharing more recent common ancestry with the clade Sauropsida than with the clade Synapsida or Mammalia. In addition, the formerly separate subclass Euryapsida has been replaced by the more general class Tetrapoda. The tetrapods include the synapsids and sauropsids, as well as the extinct mammal-like reptiles and birds. The synapsids and the tetrapods that are more closely related to each other belong to the clade Synapsida, while all remaining amniotes form the clade Euryapsida.

Sub-class Anapsida

In the sub-class Anapsida are a wide range of reptiles including snakes, lizards, and crocodiles. These reptiles have a skull with one temporal fossa located high on the skull. They are a diverse group and include Protosaurs, Nothosaurs, Placodonts, and Ichthyosaurs. They also include modern chelonians, such as turtles, tortoises, and terrapins. Skulls of this type have a large posterodorsal excavation in the skull roof and may be termed’suprafossal’, or’supracavus’ (from Latin, supra = above, fossa = cavity). This morphological feature is also seen in Cryptodira and some Gymnophiona.

It has been argued that the temporal fenestrae in early diapsids served as areas of maximum resistance against forces applied by jaw adductor muscles during feeding, thus making them an evolutionary adaptation. This idea has been argued by Versluys (1919), Carroll (1982), and Boettger (1952).

The class Anapsida is traditionally used to describe a paraphyletic assemblage of non-synapsid amniotes, which excludes the class Avisarum. However, some recent molecular phylogenies suggest that turtles are a monophyletic group within Synapsida, and should be included in this class instead of Anapsida.

In addition to the Anapsida, some researchers use a second classification scheme, based on temporal morphology. The ‘Metapsida’ and ‘Katapsida’ are two groups of amniotes that differ in their temporal fenestrae. These groups were named by Osborn (1903), and have been interpreted to be either synapsid or diapsid, depending on their skull morphology.