| Aldabra Giant Tortoise (Dipsochelys dussumieri)|
Aldabra Giant Tortoise (Dipsochelys dussumieri)
Cryptodira is the taxonomic suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira, or side-neck turtles, in that they lower their neck, and pull the head straight back into the shell, instead of folding the neck sideways along the body.
Classification and evolutionEdit
Cryptodires evolved primarily through the Jurassic period, and by the end of the Jurassic, had almost completely replaced Pleurodires in the lakes and rivers, while beginning to develop land-based species. Cryptodira has four main families:
The family Meiolaniidae was a family of giant turtles noted for having developed large bony spikes on the head and tail for protection. They were originally thought to have originated in the Oligocene, in Australian rainforests, but, the findings of fossils in South America suggest that the family originated prior to the break up of Gondwana during the Cretaceous. Meiolania was the last, and best-studied example of this family, whose last relic populations became extinct about 1700-1800 years ago at Lord Howe Island, New Caledonia.
The most successful of the cryptodires belonged to the family Testudinidae, which encompasses all modern day land tortoises. The largest known tortoise species is the now-extinct Testudo atlas which is placed in the same genus as the well-known Greek Tortoise. Examples of T. atlas have been found indicating a length of 2.50 meters (over 8 feet), and a weight of over 4 tons.
Protostegidae, an ancient family of sea turtles, these large, highly specialized turtles had lightweight shells, and broad flippers. They lacked the ability to retract their heads.
The family Trionychidae makes up most of our modern soft-shell turtles, and comprises over 32 species living in the freshwater lakes and rivers of North America, Asia and Africa.
Geoemydidae (formerly known as Bataguridae) is the largest and most diverse family in the order Testudines (turtles) with about 75 species. It includes the Eurasian pond and river turtles and Neotropical wood turtles.