**1. Reptiles**

Reptiles are one of the six main animal groups together with amphibians, invertebrates, fish, birds, and mammals. They are tetrapods that diverged from ancestral amphibians approximately 340 million years ago. There are two characteristics that early reptiles had developed when diverging from amphibians: scales and amniotic eggs (eggs with an internal fluid membrane), which are still of great importance for them. Extant reptiles are represented by four orders: Squamata (lizards, snakes and worm-lizards), Crocodilia (alligators and crocodiles), Chelonia (tortoises and turtles), and Rhynchocephalia (tuatara) [1]. Squamates are the most diverse from all of the groups and have exceptional skull mobility. The only exception to this exceptional skull mobility is the almost extinct tuatara, which only lives on a few New Zealand islands. This reptile has a skull which is not joined, the reptiles grow slowly and reproduce at a slow rate and have a prominent parietal eye on top of the head.

Snakes are carnivorous reptiles with highly mobile jaws, which enable them to swallow prey much larger than they are. They are legless (some species retain a pelvic girdle) and have an elongated body, this means that paired organs appear one in front of other and they only have one functional lung. Some species have venom, used primarily to kill prey. Their skin is covered in scales and snakes are not slimy [2]. Lizards are quadrupedal squamates, except some legless, snake-like-bodied species. Often, they are territorial and have many antipredator strategies, such as camouflage, venom, reflex bleeding, and the ability to destroy and then regenerate their tails after destruction. They are covered in overlapping keratin scales, enabling them to live in the driest deserts on the earth [3, 4].

Crocodilians are the largest reptiles, and include the alligators, crocodiles, gharials, and caimans. They have elongated, structurally reinforced skulls, powerful jaw muscles, teeth in sockets, and a complete secondary palate; they are oviparous and, interestingly, adults provide extensive parental care to young.

Turtles are among the most ancient of the reptiles alive today and have changed little since they first appeared 200 million years ago. They have a protective shell that encloses their body and provides protection and camouflage. They have keratinized plates instead of teeth and a shell that consists of a carapace and plastron [5, 6].
