Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Tetrapod, Vertebrates — Vertebrates with Amniotic Membranes
Class Reptilia, or Reptiles — Subclass Anapsida — Order Testudines — Suborder Sea Turtles

The suborder Sea turtles (Cryptodira) comprises a single family with 6 to 7 highly specialized species adapted to marine life. Their limbs are modified into flippers, with the BONES OF THE hand and FOOT flattened, elongated, and frequently lacking joints due to immovably fused structures. The carapace is less developed than in other turtles; in some species, it consists of separate bony plates that are not fused with THE Vertebral Column and Ribs. Owing to this reduced carapace development, the HEAD and limbs cannot be fully retracted into the shell.

A typical representative is the green turtle (Chelonia mydas), a large animal measuring slightly over 1 m in length and weighing up to 200 kg. It is widely distributed across tropical and subtropical seas and remains locally abundant. It predominantly inhabits coastal zones, occasionally venturing into river estuaries, and sometimes swims far out into the open ocean, frequently forming schools. It feeds on Algae and a variety of marine animals. Eggs are laid on the sandy beaches of islands, with a single female depositing up to 200 eggs in multiple clutches. The species is in need of conservation due to overfishing.

Closely related to this species is the hawksbill sea turtle, or karetta (Eretmohelys imbricata). It is smaller than the green turtle, with a carapace length reaching 60 — 80 cm. Inhabiting the coastal waters of tropical seas in both hemispheres, it feeds exclusively on aquatic animals. The hawksbill is heavily exploited commercially for its highly decorative shell scutes and is currently in need of protection.