chelonian

A chelonian is a reptile belonging to the order Testudines, which is characterized by a bony or cartilaginous shell. This shell is a defining feature, providing protection to the animal's body. Chelonians include turtles, tortoises, and terrapins. While these terms are often used interchangeably, they generally refer to different habitats. Turtles are typically aquatic or semi-aquatic, tortoises are primarily terrestrial, and terrapins are often found in brackish water environments.

The shell of a chelonian is composed of two main parts: the carapace, which is the dorsal (upper) section, and the plastron, which is the ventral (lower) section. These are fused together along the sides. The shell grows with the animal and is covered in scutes, which are made of keratin, the same material as fingernails. Chelonians are ectothermic, meaning they rely on external sources of heat to regulate their body temperature. They are found in a wide variety of habitats across the globe, from oceans and freshwater systems to deserts and forests. Their diet varies greatly depending on the species, with some being herbivores, others carnivores, and many being omnivores. Reproduction in chelonians is oviparous, meaning they lay eggs.