Pluerodirans and criptodirans

When turtles feel threatened they hide their heads. How they do it makes the difference between between the two suborders of turtles. Turtles and tortoises belong into the Order Testudines, which subdivides into Pleurodira (side-necked) and Cryptodira (hidden neck). The turtle on the left, a side-necked turtle Phrynops hilarii, hides its long neck by folding it sideways. It is a pleurodiran. Pleurodirans are found only in the Southern Hemisphere. <br />The turtle on the right, a painted turtle Trachemys dorbigni, belongs into the Cryptodira. It pulls the neck straight back into the carapace. In both cases vertebrae have adapted to move in such a way.

Side-necked turtle

Phrynops hilarii

07-04-15 © Nicolás Giorgio

Painted turtle

Trachemys dorbigni