The Emydidae, commonly called terrapins, pond turtles, or marsh turtles, are a family of turtles. Previously, several species of Asian box turtles were classified in the family. However, revised taxonomy has separated them to a different family. Now, the Emydidae, with the exception of two species of pond turtles, are entirely a Western Hemisphere family. The family Emydidae includes close to 50 species in 10 genera.
- Kingdom: Animalia
- Phylum: Chordata
- Class: Reptilia
- Order: Testudines
- Suborder: Cryptodira
- Superfamily: Testudinoidea
- Family: Emydidae
Emydidae, family of hard-shelled turtles native to both the Old and New Worlds, primarily in the Northern Hemisphere. The emydid turtles comprise more than 25 genera and 85 living species—roughly one-half of all the genera and one-third of all the species of turtles now living.
With the exception of a few terrestrial forms, such as the box turtles (Terrapene) of North and Central America, emydid turtles are aquatic reptiles with streamlined shells. Some, such as the diamondback terrapin, are valued as food; others are kept as pets.
Sizes are variable and range from only 11 cm (Clemmys) to nearly 60 cm (Kachuga) in carapace length. Coloration is also quite variable. The family doesn’t have a distinguishing suite of superficial characters. In some species, the carapace is domed, while most have a low-arching carapace. The plastron is hinged and movable in some, while fixed in others. Unanimous skeletal features are few, but include a lack of contact between the squamosal and parietal bones in the skull and the presence of the frontal bone in forming the orbit.
Food habits range from strictly carnivorous to strictly herbivorous. The carnivores feed on annelids, crustaceans, and fish. In several species, a shift from carnivory in juveniles to herbivory in adults occurs. Small mammals, especially raccoons, are responsible for the destruction of many emydid nests. The wide range of sizes in mature animals leads to an assortment of predators. While snapping turtles are responsible for predation in some smaller species, they cannot eat larger species. Alligators pose a risk to adults of several species.
The Emydidae are most closely related to the tortoises (Testudinidae) and are included along with that family in the Testudinoidea. Shared features include a lack of inframarginal scutes, the shape and muscle attachment of the ilium, and the shape of the eighth cervical vertebra (biconvex). Within the Emydidae, two subfamilies are recognized along biogeographic lines. The Emydinae contains New World species (except Emys), while the Batagurinae contains Old World species (except Rhinoclemmys).