Turtles are reptiles, most of whose body is shielded by a special bony 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. Turtles cannot breathe in water, but they can hold their breath for various periods of time.
The largest is the great leatherback sea turtle, which reaches a shell length of 80 inches and can reach a weight of over 2,000 lb, or 1 short ton. Freshwater turtles are generally smaller, but with the largest species, the Asian softshell turtle, a few individuals have been reported up to 200 cm or 80 inches.
Most turtles that spend most of their life on land have their eyes looking down at objects in front of them. Some aquatic turtles, such as snapping turtles and soft-shelled turtles, have eyes closer to the top of the head. These species of turtles can hide from predators in shallow water where they lie entirely submerged except for their eyes and nostrils. Sea turtles possess glands near their eyes that produce salty tears that rid their body of excess salt taken in from the water they drink.
