Reptile Classification

Reptiles are cold-blooded and rely on their environment to keep them warm. They have dry, rough skin and a well-developed nervous system with 12 pairs of cranial nerves. They have a three-chambered heart, and most are uricotelic (excrete nitrogen as urea).


Reptilia includes turtles and their relatives (Testudines), snakes and lizards (Lepidosauria), crocodiles and alligators (Crocodilia), and birds (Aves). They are amniotes, which means that they have a membrane protecting their eggs from environmental problems such as desiccation.


Reptiles are cold-blooded vertebrates that have scales and a bony skeleton. They are the dominant terrestrial vertebrates with 11,500 living species in nearly every habitat on earth, including forests, swamps, deserts, and oceans. The earliest known reptile is Hylonomus lyelli, a small lizard-like animal that lived during the Late Carboniferous period. The class Reptilia includes all amniotes that are not birds or mammals.

The modern reptiles are split into three major orders: Testudines (turtles, terrapins and tortoises), Squamata (lizards and snakes) and Crocodilia (crocodiles, caimans and alligators). These groups are further broken down into families and then subgroups.

Class Reptilia

The most common type of reptile is the lizard, a long and slender animal that can quickly move in search of food or to escape danger. The lizard’s body is covered with scales, and it lays eggs that are attached in a string or clumped together. Most modern lizards are venomous, which they use to kill their prey.

All reptiles have a thickened layer of fat under their skin to help them conserve heat. They have a low metabolism and are therefore cold-blooded. Unlike warm-blooded animals that can generate their own body heat, reptiles rely on the sun or shade to regulate their internal temperature. They can also change their internal temperature by moving warmed or cooler blood to different parts of the body.


The first step in reptile classification is to determine what features set them apart from other vertebrates. This will reveal their phylogenetic relationship to other reptiles and other animals.

There are many different methods for analyzing and classifying reptiles, but most are based on the characteristics that were identified by Linnaeus in 1758. These include the fact that they lay eggs connected in a chain and have flat naked ears; the fact that snakes do not have feet, but rather a pair of hemiduplicated appendages called hemipenes, and the fact that they are cold-blooded and have a dry, scaly skin.

These characteristics were important to Linnaeus because he was attempting to create a system of classification that would allow him to compare the fossils of different animals to their living descendants, and thus predict the evolution of new species. His system has been modified over time by advances in science and technology.

Classification of reptiles is a continuing process that takes into account a wide range of information, including genetics, anatomy and morphology. This will be especially important in the future as more fossils are discovered and analyzed.

Reptiles have a unique place in the history of vertebrates, as they are one of the only vertebrates that have evolved to adapt to both aquatic and terrestrial environments, making them a keystone group in most ecosystems.

A reptile’s physiology is also an important factor in its ability to survive in the wild. These adaptations include the ability to metabolize efficiently, the ability to shed old skin and grow new, and the capacity for both asexual and sexual reproduction. The reptiles of the modern world are a diverse and fascinating group that can be found in nearly every environment on the planet.