Chelydra serpentina, the American snapping turtle, is one of two extant species allocated to Chelydridae, which has a fossil record stretching back into the Eocene. Both living species in this family are known for aggressive behavior and large body size. The American snapping turtle commonly reaches between 20 and 47 cm in carapace length and can attain weights of 4.5-16 kg (10-35 lbs) (Georgia Wildlife Web 2001).
Characteristic features of Chelydridae include a large skull, slightly emarginated in the temporal regions, no parietal-squamosal contact, no connection between the maxilla and quadratojugal, a stapes enclosed by the quadrate, a hooked upper jaw, one biconvex vertebra in the neck, a 10th dorsal vertebrae lacking ribs, and the presence of inframarginal scutes (Ernst and Barbour, 1989). Members of this family can also be recognized by a keeled carapace with serrated edges and 11 peripheral bones per side, and a highly reduced, cruciform plastron. Chelydra serpentina can be distinguished from the other extant chelydrid, Macroclemys temminckii (alligator snapping turtle), by the former's lack of supramarginal scutes. Additionally, the American snapping turtle has 24 marginal scutes on the carapace and a medial ridge on the ventrum of the vomer but is lacking a medial ridge on the upper jaw (Ernst and Barbour 1989).
The range of the American snapping turtle stretches from southeastern Canada, west to the Rocky Mountains of Canada and the United States, south into Florida and Texas. Their range expands into Mexico where it continues through Central America and into Colombia and Ecuador (Ernst and Barbour 1989). Individuals have been found in every freshwater habitat imaginable and will occasionally enter brackish water, though it prefers freshwater bodies with a soft, muddy bottom and lots of vegetation or debris.
Chelydra serpentina is a highly aquatic turtle, but will leave the water to bask and is comfortable on land. Its most energetic activity occurs at night; and so during the day, if not buried in mud, it is often observed floating or resting in the sun. American snapping turtles are ambush predators and will eat almost anything they come across including insects, crustaceans, water mites, mollusks, earthworms, leeches, tubificid worms, freshwater sponges, fish, small turtles, amphibians, snakes, birds, eggs, small mammals, and various species of algae (Ernst and Barbour, 1989). If the prey will not fit into its mouth, the turtle will tear it apart with the long claws on its front limbs.
Bickham, J. W., and J. L. Carr. 1983. Taxonomy and phylogeny of the higher categories of cryptodiran turtles based on a cladistic analysis of chromosomal data. Copeia 1983:918-932
Burke, A. C. 1989. Development of the turtle carapace: implications for the evolution of a novel bauplan. Journal of Morphology 199:363-378.
Burke, A. C., and P. Alberch. 1985. The development and homology of the chelonian carpus and tarsus. Journal of Morphology 186:119-131.
Ernst, C. H., and R. W. Barbour. 1989. Turtles of the World. Smithsonian Institution Press, Washington D. C., 311 pp.
Gaffney, Eugene S. 1972. An Illustrated Glossary of Turtle Skull Nomenclature. American Musem Novitates 2486:1-33.
Gaffney, E. S. 1979. Comparative cranial morphology of Recent and fossil turtles. Bulletin of the American Museum of Natural History 164:67-376.
Gaffney, E. S. 1981. A review of the fossil turtles of Australia. American Museum Novitates 2720:1-38.
Lauder, G. V., and T. Prendergast. 1992. Kinematics of aquatic prey capture in the snapping turtle Chelydra serpentina. Journal of Experimental Biology 164:55-78.
Meier, S., and D. S. Packard, Jr. 1984. Morphogenesis of the cranial segments and distribution of neural crest in the embryos of the snapping turtle Chelydra serpentina. Developmental Biology 102:309-323.
Rieppel, O. 1990. The structure and development of the jaw adductor musculature in the turtle Chelydra serpentina. Zoological Journal of the Linnean Society 98:27-62.
Rieppel, O. 1993. Studies on skeleton formation in reptiles: patterns of ossification in the skeleton of Chelydra serpentina (Reptilia, Testudines). Journal of Zoology (London) 231:487-509.
Shaffer, H. B., P. Meylan, and M. L. McKnight. 1997. Tests of turtle phylogeny: molecular, morphological, and paleontological approaches. Systematic Biology 46:235-268.
Chelydra serpentina on the Georgia Wildlife Web (2001)
Chelydra serpentina on the Western Ecological Research Center
Images of Chelydra serpentina on Calphotos
Chelydra serpentina on Animal Diversity Web (The University of Michigan Museum of Zoology)
The research website of Dr. Eugene Gaffney of the American Museum of Natural History