A turtle is a reptile. Turtles belong to the class Reptilia, which also includes snakes, lizards, and crocodiles. Unlike amphibians, reptiles have scaly skin and lay eggs with hard shells on land. Mammals, on the other hand, are characterized by having hair or fur and the ability to produce milk to feed their young.
Turtles are easily distinguished by their bony or cartilaginous shell, which acts as a shield. This unique feature sets them apart from other reptiles. They are cold-blooded, meaning they rely on external sources of heat to regulate their body temperature.
In summary, turtles are reptiles, not amphibians or mammals. Their classification is based on their physical characteristics and biological traits.