Turtles are reptiles, most of whose body is shielded by a special bony or cartilaginous shell developed from their ribs. The earliest known turtles date from 215 million years ago, making turtles one of the oldest reptile groups and a more ancient group than lizards and snakes.
About 300 species are alive today, and some are highly endangered.
The largest turtles are aquatic. Turtles cannot breathe in water, but they can hold their breath for various periods of time.
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