Gray, 1864b
Pacific Coast giant musk turtle
Recognition
The elongated (to 25 cm), oval, adult carapace has three longitudinal keels which may become lower with age. The medial keel extends from the posterior portion of the 1st vertebral to the seam between the 11th pair of marginals. The dorsolateral keels extend along the dorsal portions of all four pleurals. Vertebrals 1-4 are longer than broad and the 5th is broader than long. Posterior marginals are somewhat flared and the 10th and 11th are elevated over the preceding nine, with the 11th highest of all; the marginal rim is smooth. The carapace of S. salvinii appears to be wider and more flattened than its congener, S. triporcatus. It is dark brown to olive gray, with or without faded mottled spots. Most of the distinguishing features are on the plastron, which is small and cross shaped and contains a hinge that allows movements of the anterior lobe. The anterior lobe is longer than the posterior lobe, and its sides converge anteriorly throughout; the posterior lobe is pointed and unnotched. Gular and humeral scutes are absent; the plastral formula is: pect > an >< fem > abd. The abdominal and femoral scutes are much wider than long. The bridge is narrow, only 10-20% of the plastral length. Large axillary and inguinal scutes are present. Both bridge and plastron are yellow to gray. The head is large, broad across the temples, has a projecting snout and a weak hook on the upper jaw. It is gray with fine orange or yellow markings and plain yellow jaws. The head becomes uniformly dark with age. Two barbels are on the chin. Limbs and tail are grayish brown, two rows of conical tubercles occur on the tail, and the toes are webbed.
Males have long, thick tails and roughened patches of scales (vinculae) on the thighs and crura. The female tail is short and she lacks the roughened scales on the hindlegs.
Distribution
Staurotypus salvinii occurs in the lowland Pacific drainages of Oaxaca and Chiapas, Mexico, southward into Guatemala and El Salvador.
Habitat
Slow-flowing waterways with soft bottoms and abundant aquatic vegetation are preferred by this species.
Natural History
Schmidt (1970) observed courtship in captivity; it occurred in water during January. While copulating, the male maintained his position on the female's carapace with his hindlegs, the roughened patches of scales aiding his grip. The female actively bit at the male's jaws. Sachsse and Schmidt (1976) reported that in addition to visual cues, olfactory releasers play a major role in sexual stimulation.
Several clutches of 6 to 10 eggs are laid each season, probably during the fall or early winter months. The brittle-shelled eggs are elongated (40 x 20 mm), and incubation periods reported by Sachsse and Schmidt (1976) ranged from 80 to 210 days. Females at the Columbus Zoo, Ohio use resources equivalent to 16.29% of their body mass to produce an average of 17.79 progeny per year (Goode, 1991). Hatchlings have carapace lengths of 25-31 mm; their plastra are variably patterned with dark mottled spots.
Like other kinosternids, S. salvinii is carnivorous. In the wild it probably feeds on aquatic insects and other invertebrates, amphibians, and small fish.
This species is well-known for its vile temper and sharp jaws!
IUCN Red List Status (1996)
Lower risk: near threatened.