Modern Forms

The name 'turtle' in scientific terms includes all forms of turtles, tortoises and terrapins. These names have been applied to infer something about the life habits of the animals concerned: turtles tend to be marine, tortoises terrestrial and terrapins freshwater.

Turtles are found in the group Testudines (or Chelonia), and a further divided into Pleurodira ('side necked') and Cryptodira ('hidden necked'). The Pleurodira make a sideways bend in the neck to retract the head, and the Cryptodira make a vertical bend.

The earliest modern turtle was Proterochersis, a pleurodire from the late Triassic of Germany, and fossil forms were worldwide in a range of habitats. Today, pleurodires are all freshwater and restricted to the southern hemisphere. The earliest cryptodire was Kayentachelys from the early Jurassic of Arizona. Most modern turtles are cryptodires, and are found worldwide.

Today there are over 290 species of turtle in 99 genera and 14 families, although many are endangered.

The Cryptodira



The Hawksbill Seaturtle (Eretmochelys imbricata), a critically endangered Caribbean turtle, 90cm long. Halliday & Adler 2004

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The Indian Star Tortoise (Geochelone elegans), dry forests in southern India, 25cm long. http://www.thebigzoo.com/animals/zoom/Geochelone_elegans_001.asp

The Pleurodira



The Matamata (Chelus fimbriatus), a large (45cm long) freshwater turtle from the Amazon basin. Halliday & Adler 2004

• Anapsida home page
• Characters and anatomy
• Major subgroups
• Fossil record
• Literature and web links