Turtles can take many years to reach breeding age, and in many cases breed every few years rather than annually. Sea turtles lay their eggs on dry, sandy beaches. The eggs of the largest species are spherical, while the eggs of the rest are elongated. Like other reptiles, turtles lay eggs which are slightly soft and leathery. The turtles can take up dissolved oxygen from the water using these papillae, in much the same way that fish use gills to respire. These projections, called papillae, have a rich blood supply, and increase the surface area. Some species have large cloacal cavities that are lined with many finger-like projections. Some spend their whole lives on dry land.Īquatic respiration in Australian freshwater turtles is being studied. Ecology and life historyĪlthough many turtles spend much of their lives underwater, all turtles and tortoises breathe air, and must surface at regular intervals to refill their lungs. Unfortunately, Chelonia is also the name of a particular genus of turtles, so this conflicts with its use for the entire order Testudines. To avoid confusion, the word "chelonian" is popular among some who work with these animals, as a catch-all name. Australian English uses turtle for both the marine and freshwater species, but tortoise for the terrestrial species.The name "terrapin" is typically reserved only for the brackish water diamondback terrapin, Malaclemys terrapin. "Tortoise" is used for most land-dwelling species, and oceanic species are usually referred to as sea turtles. American English tends to use the word turtle as a general term for all species.British English describes these reptiles as turtles if they live in the sea terrapins if they live in fresh or brackish water or tortoises if they live on land.How these names are used, if at all, depends on the type of English. But, of the many species alive today, some are highly endangered.Īlthough the word turtle is widely used to describe all members of the order Testudines, it is also common to see certain members described as terrapins, tortoises or sea turtles, as well. Turtles have been very successful, and have almost world-wide distribution. Molecular evidence shows they are definitely archosauromorphs, the group of diapsid reptiles which also includes the dinosaurs. So turtles are one of the oldest surviving reptile groups and a more ancient group than lizards, snakes and crocodiles.
The earliest fossil turtle comes from the early Upper Triassic of China, about 220 million years ago. The order Testudines includes both living and extinct species. They have a special bony or cartilaginous shell developed from their ribs that acts as a shield. Turtles are the reptile order Testudines.
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