Added 16 April 2023.

Malaclemys

Diamondback Terrapin

Malaclemys is a monotypic genus containing the single species M. terrapin. Conant and Collins call this “the most celebrated of American turtles”. At one point it was threatened by harvesting for its flesh, which was considered a delicacy, but fortunately this has decreased: however, the species remains threatened by other human activities, including alterations to the coastlines on which it lives and such accidents as being struck by motorboats or being caught in traps intended for other species. For this reason it is classified as Vulnerable by the IUCN.

Boulenger gives the characteristics of the genus as follows: neural plates hexagonal, short-sided in front. Plastron extensively united to the carapace by suture, with feeble axillary and inguinal peduncles, the latter anchylosed to the fifth costal plate; entoplastron anterior to the humero-pectoral suture. Skull with a bony temporal arch: alveolar surface very broad, without median ridge; choanae behind the level of the eyes. Upper surface of head covered with undivided skin. Digits webbed. Tail short.

The Diamondback Terrapin has a wide distribution along the east coast of the USA, from Massachusetts in the northeast all along the Atlantic to Florida, including the Keys, and as far as southern Texas. Seven subspecies are recognised, although Conant and Collins note that individual variation is great, making identification difficult: hence place of origin (if known) is fairly important. Habitat is coastal marshes, where they live in salt or brackish water.

Müller considers this species to be unsuitable for beginners, calling its keeping “problematic”, partly because of the requirement for brackish water.

Species Name	Common Name	Location	Size	Notes
M. terrapin	Diamondback Terrapin	E & SE USA, E Mexico	Max >>	Carapace: much depressed, oval, posterior border sometimes distinctly reverted, very rarely serrated; a more or less strong, interrupted, vertebral keel or series of subconical tubercles; dorsal shields concentrically grooved, or smooth; nuchal moderate, as broad as long or a little broader than long; first vertebral broader anteriorly than posteriorly; vertebrals 2 to 4 much broader than long, broader than costals. Plastron: a little smaller than the opening of the shell, obtusely angulated laterally; bridge rather narrow, its width considerably less than the length of the hind plastral lobe; latter openly notched posteriorly; relative proportions of the plastral shields very variable; the suture between the abdominals and that between the anals are of equal length, or the latter is the shorter; pectorals usually much smaller than abdominals, sometimes very slightly smaller; axillary and inguinal rather small. Head: large; snout short, more or less obtusely pointed; upper beak pendent, not hooked, forming an open notch mesially; alveolar surface of upper jaw narrowing towards the symphysis; the width of the mandible at the symphysis equals or a little exceeds the horizontal diameter of the orbit. Limbs stout, tubercular rather than scaly. Tail: measures about two fifths the length of the carapace in the male, less in the female; a low dorsal crest of enlarged compressed scales on the postanal part of the tail. Coloration: carapace olive, with black concentric lines, or uniform blackish; plastron yellowish or reddish, blotched, speckled, or vermiculated with black, or with black concentric lines. Soft parts grey, spotted or vermiculated with black. [SOURCE: Boulenger]
M. t. terrapin	Northern Diamondback Terrapin	SE USA (N Carolina to Mississippi, excluding Florida: isolated colony in SE Virgina)	Max ??	??
M. t. centrata	Carolina Diamondback Terrapin	E USA as far as the Florida peninsula	Max 20cm	??
M. t. littoralis	Texas Diamondback Terrapin	USA (S Texas)	Max 20cm	Found along coast of Texas. Coloration: skin greenish-grey, heavily marked with black spots; plastron nearly white; normally lacks “moustache”. [SOURCE: Conant & Collins]
M. t. macrospilota	Ornate Diamondback Terrapin	USA (S & W coasts of Florida)	Max 20cm
M. t. pileata	Mississippi Diamondback Terrapin	USA (Gulf coast of Florida westwards to Louisiana)	Max 23.8 cm	Found in marshes and estuaries. Carapace: strongly tuberculate central keel; edges of shell turned upward. Coloration: carapace usually uniform black or brown; skin very dark; plastron yellow, often clouded with a dusky shade; edges of shell orange or yellow; most females and some females with black “moustache” on upper jaw. [SOURCE: Conant & Collins]
M. t. rhizopharum	Mangrove Diamondback Terrapin	SE USA (Florida Keys)	Max 20cm	Carapace: bulbous bumps on dorsal keel. Coloration: dark spots on neck fused together to produce streaked appearance. [SOURCE: Conant & Collins]
M. t. tequesta	Florida East Coast Terrapin	USA (E coast of Florida from Valusia County southwards to Dade County)	Max 22cm	Coloration: carapace dark or horn-coloured, lacking pattern of concentric circles; centres of large scutes only a little lighter than areas surrounding them. [SOURCE: Conant & Collins]

Biography

Turtles and Tortoises of the World, David Alderton, Blandford, London 1999.

A Field Guide to Reptiles and Amphibians of Eastern and Central North America, R Conant and J T Collins, Peterson Field Guides, Houghton Mifflin, Boston/New York 1998.

Schildkröten, Gerhard Müller, Eugen Ullmer, Stuttgart 1995.

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