Chelonians are a group of reptiles that include turtles, tortoises, and terrapins. They are characterized by their bony or cartilaginous shell, which protects their bodies. Chelonians are found in various habitats, including oceans, rivers, and land, and they can be both aquatic and terrestrial. These animals are known for their slow movement and long lifespan. Chelonians are ectothermic, meaning they rely on external temperatures to regulate their body heat. They play important roles in their ecosystems, such as controlling aquatic vegetation and serving as prey for larger animals like alligators and birds of prey.