Scientists divide turtles into how they retract their heads into their shells.
Turtles who bend their necks vertically are called Pleurodira, while those that bend their neck back vertically are called Cryptodira. When the neck is retracted vertically, it forms an S inside the shell. There was another order called Proganochelydia, but they’re extinct now.
[wp_ad_camp_1]
