Emydidae (

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''emys'' (freshwater tortoise) +

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

εἶδος (''eîdos'', “appearance, resemblance”)) is a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

testudine Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tur ...

s (turtles) that includes close to 50

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

in 10

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

. Members of this family are commonly called terrapins, pond turtles, or marsh turtles. Several species of Asian box turtles were formerly classified in the family; however, revised

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

has separated them to a different family ( Geoemydidae). As currently defined, the Emydidae are entirely a

Western Hemisphere The Western Hemisphere is the half of the planet Earth that lies west of the prime meridian (which crosses Greenwich, London, United Kingdom) and east of the antimeridian. The other half is called the Eastern Hemisphere. Politically, the te ...

family, with the exception of two species of pond turtle.

Description

The upper shell (

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

) of most emydids is the shape of a low arch, although in some species, it is domed. The upper shell may have one or two ridges that run from front to the back of the animal (a projection commonly called a "keel"), or such a feature may be absent. A prominent bridge often connects the top shell to the bottom shell ( plastron). Emydids have large bottom shells, and some members of the family have a movable hinge that separates pectoral and abdominal segments ( scutes). The skull is small. The limbs of these turtles are adapted for swimming, with every member having some level of toe webbing. Most species exhibit temperature-dependent sex determination, as is typical of turtles; however, one species (the wood turtle) is known to have genetic sex determination.

Behavior

Food habits range from strictly

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

to strictly herbivorous. The carnivores feed on

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s, 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 turtle The Chelydridae is a family of turtles that has seven extinct and two extant genera. The extant genera are the snapping turtles, ''Chelydra'' and ''Macrochelys''. Both are endemic to the Western Hemisphere. The extinct genera are ''Acheronte ...

s are responsible for predation in some smaller species (e.g., ''Glyptemys muhlenbergii''), they cannot eat larger species.

Alligator An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additional ...

s pose a risk to adults of several species. Knowledge of reproductive behavior ranges from some of the most detailed, long-term study of any

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

(''Chrysemys picta'' in Michigan) to a total lack of information. In many species, dimorphisms include elongated foreclaws or a concave plastron in the male. The longer claws are used in a courtship routine in which the male faces the female and fans her face. The concave plastron allows the male to mount females in species with more domed carapaces (e.g., ''Terrapene''). Reproduction is on an annual cycle, and multiple clutches may be produced in a single season. Clutch size is quite variable, ranging from as few as two to more than 30 eggs.

Threats

Emydids are the turtles most commonly sold through the pet trade. The

pond slider The pond slider (''Trachemys scripta'') is a species of common, medium-sized, semiaquatic turtle. Three subspecies are described, the most recognizable of which is the red-eared slider (''T. s. elegans''), which is popular in the pet trade and ha ...

(''Trachemys scripta'') has expanded its range through the careless release of pets into the wild. Many Asian species are threatened by over-collection of animals for sale in markets and into the pet trade. The North American species ''Clemmys muhlenbergii'' is listed as an Appendix II species by

CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of intern ...

and is considered threatened or endangered in many states. This status is the result of habitat degradation and over-collection.

Systematics and evolution

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 were recognized along biogeographic lines. The Emydidae as understood today contain New World species (except ''

Emys ''Emys'' is a small genus of turtles in the family Emydidae. The genus (''sensu lato'') is endemic to Europe and North America. Species The following two species may be assigned to the genus ''Emys'' (''sensu lato''). ''Nota bene'': A binom ...

''), while the former Batagurinae, today a separate family Geoemydidae, contain Old World species (except ''

Rhinoclemmys ''Rhinoclemmys'' is a genus of turtles in the family Geoemydidae (formerly Bataguridae), the only genus in the subfamily Rhinoclemmydinae. Member species of the genus are commonly known as the Neotropical wood turtles and are the only geoemydids ...

''). Osteological characters, such as the construction of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

and articulations of the cervical vertebrae distinguish the two families. The enigmatic

big-headed turtle The big-headed turtle (''Platysternon megacephalum'') is a species of turtle in the family Platysternidae from Southeast Asia and southern China. Background Previously considered a distinct family placed on occasion in " Kinosternoidea", i ...

(''Platysternon megacephalum'') was for some time considered a specialized, but still very primitive early offshoot of the Emydidae. With the Geoemydidae being split off, though, it is better reinstated as its own family, the Platysternidae, though it seems very close to the emydid-geoemydid group.

Fossil record

Presumed emydids are well represented in the

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record. '' Gyremys sectabilis'' and '' Clemmys backmani'' are both North American species that date from the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

and

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...

, respectively. These are the two oldest fossil species. Many other extinct species traditionally placed in the Emydidae are known from the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

of North America, Asia, and Europe, but the Old World taxa are likely to be more properly Geoemydidae. The North American genus '' Palaeochelys'' and probably the trans-

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

'' Echmatemys'', too, would seem to be Emydidae, but their precise relationships to the living genera are indeterminate.

Classification

The two subfamilies and genera are arranged as follows: *Subfamily Emydinae **Genus ''

Clemmys ''Clemmys'' is a genus of turtles currently containing a single extant species, the spotted turtle ''(Clemmys guttata)''. Taxonomy In the past, several other species were included in the genus, including a number of fossil species. DNA analysis ...

'' **Genus ''

'' **Genus '' Actinemys'' **Genus ''

Emydoidea Blanding's turtle (''Emydoidea blandingii'') is a semi-aquatic turtle of the family Emydidae. This species is native to central and eastern parts of Canada and the United States. It is considered to be an endangered species throughout much of its ...

'' **Genus ''

Glyptemys ''Glyptemys'' is a genus of turtles in the family Emydidae. It comprises two species, the bog turtle and wood turtle, both of which are endemic to North America. Until 2001, these turtles were considered members of the genus '' Clemmys'', which ...

'' **Genus '' Terrapene'' **Genus '' Wilburemys'' sp. '' Wilburemys yakimensis'' *Subfamily

Deirochelyinae The Deirochelyinae are a subfamily of the Emydidae consisting of species native to North America, North and South America, some of which are frequently kept as pets. As a result of pet trade, one species, the red-eared slider, can now be found i ...

**Genus '' Chrysemys'' **Genus '' Deirochelys'' **Genus ''

Graptemys ''Graptemys'' is a genus of freshwater turtles containing 14 species, commonly known as map turtles. Crother, B. I. (editor) (2017). Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments ...

'' **Genus '' Malaclemys'' **Genus '' Pseudemys'' **Genus '' Trachemys'' *Classif''ied subfamily **Genus '' Psilosemys'' sp. '' Psilosemys wyomingensis''

References

;Bibliography * *

External links

*
University of Michigan Animal Diversity Web the European pond turtle (''Emys orbicularis'')
{{Taxonbar, from=Q390835 Taxa named by Constantine Samuel Rafinesque Turtle families Cenomanian first appearances Extant Cenomanian first appearances