Cheloniidae Family of Sea Turtles

Four Sea Turtles of the Cheloniidae Family can be found in this website:

Phylogeny: Sea Turtles of the Cheloniidae Family belong, like humans, to the phylum Chordata. Like lizards and snakes, they are in the class Reptilia. Cheloniid Sea Turtles are in the order Testudines, the suborder Cryptodira, and the superfamily Chelonoidea. The superfamily Chelonoidea contains two families- the Dermochelyidae family (with one living species, the Leatherback Sea Turtle, Dermochelys coriacea) and the Cheloniidae Family. The Cheloniidae Family is comprised of seven genera, two of which no longer contain accepted species. There are six accepted species in the Cheloniidae Family and three subspecies. The name Cheloniidae comes from the Greek word meaning “turtle” or “tortoise”. Sea Turtles in this family are also commonly called Cheloniids and Typical Sea Turtles.

Morphology:  Cheloniid Sea Turtles are air breathing, have hard plates (scutes) covering their shells that are made from a substance similar to the main component of cattle horns, and a three chambered heart. They have a hard, bony, upper (carapace) and lower (plastron) shell covering their bodies. Their ribs and vertebrae are fused to the carapace. Their shells are oval or slightly heart-shaped and are low to reduce drag through the water. Unlike most turtles, Sea Turtles cannot retract their head into their shell. They have beaks instead of teeth, lay eggs, and they have four legs for walking or swimming. Sea Turtles are the only turtles whose front legs are stronger than their rear legs. The legs are modified into paddles to assist with swimming. Their legs cannot support their body weight on land. Sea Turtles lack external ears but have eardrums covered by skin and have good hearing, especially in the lower frequencies. They have a very good sense of smell and good underwater eyesight. They spend the great majority of their life at sea but must come ashore to lay eggs. Cheloniid Sea Turtles are large, with the largest having a carapace length of 2.13 m (7 feet 2 inches).

Habitat and Distribution:  Cheloniid Sea Turtles are found swimming in open water or resting under overhanging reefs. They spend the majority of their time in shallow water to obtain access to air for breathing but can dive to depths in excess of 290 m (960 feet). Cheloniid Sea Turtles are found worldwide in temperate to tropical seas. Four species from the Cheloniidae Family are found in Mexican waters.

Reproduction: Sea Turtles are gonochoric (male or female for life). Reproduction is sexual with fertilization occurring internally. After mating at sea, the female visits a wide beach, at night. She digs nesting holes, using her rear flippers. She lays her eggs in the hole and buries them with sand. The young hatch out as small versions of the adults. The hatchlings need to make their way across the beach and out to open water while quite helpless from predation. Sea Turtles lay large numbers of eggs multiple times a year, and are long lived, which helps to offset the large loss of their eggs and juveniles.

Ecosystems Roles: Cheloniids are omnivores that consume algae, cnidarians, crustaceans, fish, mollusks, plants, and sponges. In turn adult Sea Turtles are preyed upon by crocodiles, groupers and sharks. While ashore laying eggs, the females are preyed upon by coyotes, wild dogs, jaguars, and other large predator mammals. Their eggs are also vulnerable to these predators, as well as shore birds, insects, and small mammals. Newly hatched juvenile sea turtles are prey for a wide variety of birds, fish, invertebrates and mammals.