Reptiles, the class of reptiles, are an evolutionary grade of animals. The reptile family consists of an order and a large family of class one species that have all evolved from each other. These 3 groups are Crocodilian, Squamata and Testudines. Reptiles have existed for millions of years. The earliest known reptiles originated 340-335 million years ago during the Carboniferous Period, having evolved from advanced reptile-like amphibians that increasingly adapted to life on land. Although there are some reptiles that live on land, on water, or on land and in water, reptiles come in different shapes, sizes, and colors. There are many different groups of reptiles that have become extinct due to massive extinction events. Reptiles are tetrapod vertebrates, meaning they have four limbs, or like snakes they descend from limbed ancestors. Most reptiles are oviparous, meaning they have egg layers, although there are some reptiles that are viviparous, meaning they carry a fetus in their stomach. The crocodile has 25 species, the squamata have over 9,600 species, and the testudines have approximately 400 species. The crocodile is an order of large predatory semiaquatic reptiles that have existed for millions of years. About 83.5 million years ago is when the crocodile first appeared, the crocodile family consists of alligators, caimans and the gharial family. Crocodiles are a solid and massive lizard like reptile, they have a long, flattened snout and a compressed tail. Crocodiles are elite swimmers and can also move on land in a "high or low walk"; some smaller species can even gallop. These reptiles have a four-chambered heart that is somewhat similar to birds and have a one-way loop system... center of the card... fascinating groups about the world's species. Some of these species can live for decades, be it turtle lizards, snakes, and these animals date back to the Jurassic Park era. Reptiles come in all shapes and sizes, some have scales and others have a shell, but they are all cold-blooded animals. All reptiles fall into an order, some being higher in the order than others. The classification of reptiles is difficult to distinguish unlike other animals because the main evolutionary period occurred during the Mesozoic period. Scientists are still studying these amazing creatures, learning more and more about the era from which they originated. It's amazing to think that some of these creatures' ancestors once hung out with dinosaurs. The reptile family consists of an order and a large family of class one species that have all evolved from each other