This is a family of hard shelled sea turtles of tropical and sub-tropical waters around the world, some occasionally wander into temperate waters during the summer. There are 5 living genera with 7 species, and about 25 other genera known only from fossil material extending back to the Cretaceous. Cheloniidae is the sister taxa to the leatherback sea turtles Dermochelidae. These turtles rarely come out of the ocean, normally only the females leave the water to deposit eggs in a nest. The front limbs have been modified into large paddles, the hind limbs are smaller and serve as rudders with the toes joined by extensive webbing. Archie Carr became very pessimistic about the plight of the green turtle. In his excellent book 1967 book, So Excellent a Fishe, he wrote:
"I use to believe that the green turtle would not be threatened by the fishermen who net and harpoon them. It seemed to me that effective protection of the nesting colony alone would save the species. I no longer believe this. It is now clear that people are so abundant, and the life cycle of a sea turtle so complicated, that nobody really knows what he is doing to a population when he kills a turtle or takes the eggs from a nest. The capacity of people to consume and their ability to destroy are growing beyond the tolerance of the small populations in which sea turtles live."
Loggerhead, Caretta caretta Rafinesque, 1814. Captive specimen, Florida. Loggerheads may reach more than 1.2 m in length and attain 227 kg. They are widely distributed in the Atlantic and Caribbean, but also occur along the west coast of North and South America, and are known from Hawaii. While they tend to be tropical and subtropical they will range into the northern temperate latitudes. This turtle appears to be the sister species to the hawksbill turtle, Eretmochelys imbricata.
The Common Green Turtle, Chelonia mydas (Linnaeus, 1758). Captives (top two photos Florida, USA), bottom photo southern Thailand). The green turtle is the world's most economically important reptile. It reaches 1.5 m in carapace length and attains weights exceeding 295 kg. The name comes not from its external coloration, but from the color of its fat which is a highly prized delicacy in many parts of the world. It occurs in all temperate and tropical oceans.
The Atlantic Hawksbill, Eretmochelys imbricata (Linnaeus, 1766). Photograph of a captive specimen, Florida. Readily recognized by its elongated shell and narrow head. This is a relatively small sea turtle, the carapace length is usually less than 950 mm. It is restricted to tropical waters in the Atlantic, Pacific and Indian Oceans. While some long distance movements have been recorded, it is considered to be non-migratory. Hawksbills feed on invertebrates, and interestingly they feed on sponges that have a skeleton composed of silicate minerals. This is comparable to eating glass. Clutch sizes are quite variable from one population to another, and they are often large, 53-176 eggs. Females rarely lay eggs in two consecutive years.
