Reptiles (Reptilia) are a class of vertebrate amniotic animals provided with epidermal keratin scales. They were very abundant in the Mesozoic, at which time dinosaurs, pterosaurs, ichthyosaurs, plesiosaurs and mosasaurs arose. According to traditional taxonomy, reptiles are considered a class, but according to cladistic systematics, they are a paraphilic group (which does not include all their descendants), therefore without taxonomic value. Birds and mammals are traditionally considered independent classes, while their ancestors of flaky skin and without feathers or hairs are usually classified within reptiles. Instead, the use of the Sauropsida clade (modern reptiles + birds) has been preferred because it is monophyletic.
Most reptiles have adapted to terrestrial life, but it has finally been discovered that some live in water. A resistant and flaky skin is one of its adaptations. Other adaptations that have contributed to the success of reptiles on the mainland are that they include well-developed lungs, a dual-circuit circulatory system, an excretory system that conserves water, strong limbs, internal fertilization, and eggs with shell eggs. In addition, reptiles can control their body temperature by changing places.
Reptiles are vertebrate animals that are characterized by their special way of walking, since they are dragging the belly along the ground. Their skin is covered with scales or they have a shell (turtles). His breathing is pulmonary. They have double and incomplete circulation because there is no total separation between arterial and venous blood. They are carnivores and hunters. They have teeth that cut but do not chew and in some cases are poisonous. Body temperature is very variable. They are oviparous. All have four legs except snakes. They are turtles, lizards, crocodiles and snakes.
With reptiles the process of animal colonization of the terrestrial environment is completed because, in addition to moving, they also reproduce. The Reptiles reached their peak during the Secondary Era, where a large number of species were found, some of them of gigantic size such as Dinosaurs, Diplodocus, Iguanodontes, Plesiosaurus, Ictiosaurs, etc., known for their remains fossils