Pacific pond turtle (Clemmys marmorata) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

The Pacific pond turtle (Clemmys marmorata) is one of four species in the genus Clemmys, Family Emydidae (Crother et al. 2000). Clemmys species are known collectively as the American pond turtles as they are restricted to North America (ibid.), and all are at some risk of extinction in Canada and the United States (R. Brooks, pers. comm.).

Clemmys marmorata has been subdivided into a northern and southern subspecies: C.m. marmorata, the northern Pacific pond turtle, and C.m. pallida, the southern Pacific pond turtle (Crother et al. 2000). These subspecies intergrade in the San Francisco Bay area (Carr 1952). Recent genetic analysis has shown that the northern inland populations are genetically distinct from one another, whereas northern coastal populations are not (Gray 1995). Southern populations also remain genetically similar. Based on differences in cytochrome b, Gray (1995) determined that Oregon (and presumably more northerly) populations are fairly recent invaders from northern California, and that Baja California populations may be distinct enough to be a separate species.

[Author’s note: Recent genetic work by Bickham et al. (1996) and Burke et al. (1996) has shown that the Clemmys genus may be paraphyletic, thus necessitating a new generic arrangement. C. marmorata may be more closely related to Emydoidea blandingii and Emys orbicularis than C. insculpta and C. muhlenbergii (a sister clade) or C. guttata (a monospecific clade) (Ernst 2002; Crother et al. 2000).]

Description

The Pacific pond turtle is a medium-sized species with a carapace length of 9-18 cm (Holland 1985). The carapace is smooth and keelless with a pattern of spots or lines radiating out from the centres of the scutes (Ernst et al. 1994). Carapace ground colour varies from olive to nearly black, sometimes with a mottling pattern (Carr 1952). The plastron is hingeless, and pale yellow with irregular dark blotches along the hind edges of the scutes (Ernst et al. 1994). Skin colour is gray with pale yellow on the neck, chin, forelimbs and tail (ibid.)

There is no significant size difference between males and females; however, males have a concave plastron and a slightly lower carapace height (Carr 1952). Ernst et al. (1994) state that females show more shell patterning than males, although Carr (1952) states the opposite. The male’s cloacal vent is posterior to the margin of the carapace; the female’s is ventral to the margin (Ernst et al. 1994). Juvenile Pacific pond turtles differ from adults by having a keeled carapace and a relatively longer tail (Carr 1952).