Chelydra serpentina (Linnaeus, 1758)
Key Characters: Long neck; long tail with sawtooth projections on upper surface; carapace strongly serrate posteriorly, with three low keels (disappear with age) and one row of marginal scutes.
Similar Species: Alligator Snapping Turtle, Macrochelys temmincki, is larger as an adult, has three longitudinal keels on the carapace throughout life, has a lure appendage on the tongue, and an extra row of marginals (=supramarginals) between true marginals 4-7 and the pleurals. See Key to Adult Turtles of Illinois for help with identification.
Subspecies: Previously two subspecies were recognized in the U.S., the Common snapping turtle, C. s. serpentina, and the Florida Snapping Turtle, C. s. osceola Stejneger (1918, Proc. Biol. Soc. Washington 31: 89-92) but recent molecular data (Shaffer et al. 2008, in Steyermark et al., Biology of the Snapping Turtle) does not support this differentiation and no subspecies are currently recognized in the U.S.
Description (modified from Smith, 1961): Large (up to 49 cm CL), aquatic turtle with an enormous head, moderately hooked beak, thick, powerful legs, and a relatively long tail; carapace in young with 3 longitudinal keels, in adults with keels worn off, but rough and usually coated with algal growth; posterior edge of carapace serrate; plastron cruciform (cross-shaped) and inadequate to conceal legs, neck, and tail; head pointed and covered with tubercules, jaws powerful; small paired gular (on chin) barbels; underside of tail plated with large scales; feet broad with long claws and extensive webbing between toes; relatively unpatterned carapace in cryptic shades of brown, olive, gray, or black. Male grows larger, has thicker tail base, and vent opening behind edge of carapace.
Habitat: Almost any body of water. Shallow, mud-bottomed backwaters and ponds with lush aquatic vegetation are especially favorable.
Natural History: Aggressive and menacing when encountered on land, but calm and retiring in water, where it seeks only escape when approached by humans; thus, it is little threat to swimmers. Although chiefly aquatic, it is often found away from water during spring. Eats a variety of invertebrates, vertebrates, and plants. Female lays one clutch of 20-40 spherical, leathery-shelled eggs (ca. 25-27 mm diameter) from mid-May to mid-June.
Status: Although many individuals are killed on roads and this species is heavily exploited for human food, populations appear not to be threatened at this time. Common statewide in habitats not used by fishermen.
Etymology: Chelydra – chelyros (Greek) for tortoise, turtle, water-serpent; serpentina – serpentis (Greek) for snake.
Original Description: Linnaeus, C. 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species cum characteribus, differnetiis, synonymis, locis. 10th ed. Vol. 1. L. Salvius, Stockholm. iv + 826 p.
Type Specimen: Andersson (1900.Catalogue of Linnean type-specimens…Royal Museum of Stockholm) stated that the holotype was originally in the NRM but was lost. Iverson (1992, A Revised Checklist with Distribution Maps of the Turtles of the World) stated that NRM GA 49 is the holotype according to Wallin (pers. comm.)
Type Locality: “in Calidis regionibus”. Restricted to New Orleans, Louisiana by Smith & Taylor (1950, Bull. U.S. Nat. Mus. 199); restricted to vicinity of New York City by Schmidt (1953, Checklist, 6th ed.)
Original Name: Testudo serpentina Linnaeus, 1758
Nomenclatural History: The most recent taxonomic changes are the elevation of the Central American subspecies to species and the lack of recognition of the subspecies C. s. osceola. See Shaffer et al. in Steyermark et al., 2008, Biology of the Snapping Turtle for more details.