Chelidae

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Several Chelid species have long necks, earning them the common name "snake-necked" turtles.

The family Chelidae contains approximately 40 species within 11 genera. Members are distributed in Australia, New Guinea, and South America. Most species inhabit slow-moving streams, rivers, and swamps, although Rheodytes appears to prefer faster-moving waters.

Chelidae is one of two families of sideneck turtles (the other is Pelomedusidae). The carapace is usually oval in shape and dark in coloration, and may be arched and keeled or depressed and grooved. The neck is often quite long, giving rise to the common designation of "snake-necked" turtle in some Australian species. The Chelids are diagnosed by extensive cheek emargination, the lack of the mesoplastral bone and qudratojugal, and the shape of the cervical vertebrae among other characters.

The natural history of many Chelids is poorly known. Most of these turtles are carnivorous, feeding on mollusks, crustaceans, aquatic insects, fish, and amphibians. Some species are omnivorous. For those species in which it has been described, courtship involves the male rubbing his chin on the carapace of the female and moving anterior along the shell, until he mounts her and copulation commences. Females subsequently lay clutches of as few as one or as many as 28 eggs.

The Chelids and the Pelomedusidae are united by their side-necked retraction of the head and are together known as the Pleurodira. Skeletal features associated with this feature include the articulation of the cervical vertebrae and the morphology of the jaw-closing musculature. No subfamilies within the Chelidae are recognized.

The fossil record for the Chelidae dates to the Miocene. Their distribution appears to have been constant across time, as fossils have only been found in South America and the region in and around Australia. Chelus and Emydura appear to be the oldest genera, and both are extant.

Ernst, C.H., and Barbour, R.W. 1989. Turtles of the World. Smithsonian Inst. Press, Washington, D.C

Pough, F.H., Andrews, R.M., Cadle, J.E., Crump, M.L., Savitzky, A.H., and Wells, K.D. 2000. Herpetology, 2nd ed. Prentice Hall, Upper Saddle River, NJ.

Contributors

Keith Pecor (author).

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

motile

having the capacity to move from one place to another.