I. Scientific Classification.

A. Class Reptilia.

1. Reptilia is a class of ectothermic (cold-blooded) vertebrates that includes snakes, lizards, crocodiles, and turtles.

2. Reptiles have scaly skin, breathe air with lungs, and have a three-chambered heart.

3. Most reptiles lay eggs, although some produce eggs that hatch internally.

B. Order Testudines.

This order includes all turtles and tortoises. It is divided into three suborders: Pleurodira (side-necked turtles), Cryptodira (all other living species), and Amphichelydia (extinct species).

C. Suborder Cryptodira.

This suborder includes freshwater turtles, snapping turtles, tortoises, soft-shelled turtles, and sea turtles.

D. Families.

Most scientists recognize two families of sea turtles:

1. Family Cheloniidae are sea turtles with shells covered with scutes (horny plates).

2. Family Dermochelyidae are scuteless turtles with only one modern species, the leatherback turtle. Leatherbacks are covered with leathery skin. They are the only marine turtle whose backbone is not attached to the inside of the shell.

E. Genus, species.

Most scientists recognize eight species of sea turtles:

1. green Chelonia mydas

2. black (also know as Eastern Pacific green turtle) Chelonia agassizii

3. loggerhead Caretta caretta

4. Kemp's ridley Lepidochelys kempii

5. olive ridley Lepidochelys olivacea

6. hawksbill Eretmochelys imbricata

7. flatback Natator depressus

8. leatherback Dermochelys coriacea

F. Fossil record.

1. The first turtles appeared during the Triassic period, 245 to 208 million years ago.

2. The earliest known sea turtles appear in the fossil record in the Late Jurassic period, 208 to 144 million years ago. Scientists believe that modern sea turtles are derived from marsh-inhabiting ancestors that lived during the Late Triassic period.

3. Fossil records show that the now-extinct sea turtle Archelon ischyros, from the Late Cretaceous period, 144 to 65 million years ago, was one of the largest turtles that ever lived and reached a length of 3 to 4 m (9.8 - 13 ft.).

4. Together with saltwater crocodiles, marine snakes, and marine iquanas, sea turtles are the only surviving seawater-adapted reptiles.



Source: Sea World