Overview #
The tortoises, terrapins and turtles together comprise the order Chelonia one of the most ancient, distinctive and familiar of all reptile groups. Modern classification systems divide the order into 12 families and around 257 species.
Chelonians occur extremely widely in tropical and temperate regions of the world, including all the major oceans. They are a diverse group, ranging in size from the diminutive, 10 cm Speckled Tortoise of South Africa to the vast ocean-going Leatherback Turtle that can weigh up to 910 kg.
Sea turtles have been on earth for over 100 million years.
Turtles, like other reptiles such as crocodiles, lizards and snakes have scaly skin, breathe air, lay eggs, and have body temperatures that fluctuate with the temperature of their environment.
The hard bony shell, or carapace, on the back of the turtle offers protection from enemies. It is composed of living tissue that includes the ribs and vetebrae along with bony elements that evolved from the scaly skin.
The front and rear flippers of the sea turtle have been specially adapted for swimming. Although sea turtles can swim under water for long periods of time, they will drown if they are unable to come up for air.