The diamondback terrapin
The diamondback terrapin belongs to the order Testudines along with all other extant Turtles. Malaclemys terrapin is the only member of the genus, and is closely related to large genus of North American map turtles, Graptemys. Malaclemys has been divided into seven different subspecies, but these divisions are generally not supported by molecular analyses. Although sometimes superficially similar to sea turtles in shape, having webbed feet and thinner shells than fully terrestrial tortoises, terrapins do not belong to the sea turtle superfamily Chelonioidea. In British English, the species most commonly referred to as terrapins are members of the family Emydidae including the red-eared slider Trachemys scripta elegans and the painted turtle Chrysemys picta. Perhaps confusingly, although the genus to which the box turtles belong, Terrapene, sounds similar to the word terrapin, these turtles are not normally called terrapins, but are also in the turtle family Emydidae. Americans only use the term “terrapin” to refer to Malaclemys terrapin, which makes sense considering the meaning of the word.