Emydidae (

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin

''emys'' (freshwater tortoise) +

Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the diale ...

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

family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...

of testudines (turtles) that includes close to 50

species In biology, a species is the basic unit of biological classification, 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 individu ...

species

in 10

genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...

. Members of this family are commonly called terrapins, pond turtles, or marsh turtles. Several species of

Asian box turtle Asian box turtles are turtle Turtles are an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, ...

s were formerly classified in the family; however, revised

taxonomy Taxonomy is the practice and science of categorization Categorization is the human ability and activity of recognizing shared features or similarities between the elements of the experience Experience refers to conscious , an English Par ...

has separated them to a different family (

Geoemydidae The Geoemydidae (formerly known as Bataguridae) are one of the largest and most diverse Family (biology), families in the order Testudines (turtles), with about 70 species. The family includes the Eurasian pond and river turtles and Neotropical ...

). As currently defined, the Emydidae are entirely a

Western Hemisphere The Western Hemisphere is the half of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining ...

family, with the exception of two species of

pond turtle

Description

The upper shell (

carapace A carapace is a Dorsum (biology), 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 tor ...

) 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 The turtle shell is a shield for the ventral and dorsal parts of turtles (the Order (biology), order Testudines), completely enclosing all the vital organs of the turtle and in some cases even the head. It is constructed of modified bony elements ...

). Emydids have large bottom shells, and some members of the family have a movable hinge that separates pectoral and abdominal segments (

scutes A scute or scutum (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

). 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 Temperature-dependent sex determination (TSD) is a type of environmental sex determination Environmental sex determination is the establishment of sex by a non-genetic cue, such as nutrient availability, experienced within a discrete period after ...

, as is typical of turtles; however, one species (the

wood turtle The wood turtle (''Glyptemys insculpta'') is a species of turtle endemism, endemic to North America. It is in the genus ''Glyptemys'', a genus which contains only one other species of turtle: the bog turtle (''Glyptemys muhlenbergii'' ). The wo ...

) is known to have genetic sex determination.

Behavior

Food habits range from strictly

carnivorous A carnivore , meaning "meat eater" (Latin, ''caro'', genitive ''carnis'', meaning "meat" or "flesh" and ''vorare'' meaning "to devour"), is an organism, animal whose food and energy requirements derive solely from animal Tissue (biology), tissu ...

to strictly

herbivorous A herbivore is an animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All ...

. The carnivores feed on

annelid The annelids (Annelida , from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share ...

crustacean Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, Caridea, shrimp, krill, Dendrobranchiata, prawns, woodlice, barnacles, copepods, amphipoda, amphipods and mantis shrimp. The ...

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 turtles are responsible for predation in some smaller species (e.g., ''Glyptemys muhlenbergii''), they cannot eat larger species. Alligators 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 (''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 (''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 and is considered threatened or endangered in many states. This status is the result of habitat destruction, 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 (bone), 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''), while the former Batagurinae, today a separate family

, contain Old World species (except ''Rhinoclemmys''). Osteological characters, such as the construction of the mandible and articulations of the cervical vertebrae distinguish the two families. The enigmatic big-headed turtle (''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 record. ''Gyremys sectabilis'' and ''Clemmys backmani'' are both North American species that date from the Upper Cretaceous and Paleocene, respectively. These are the two oldest fossil species. Many other extinct species traditionally placed in the Emydidae are known from the Eocene 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 ''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'' **Genus ''Emys'' (includes ''Actinemys'' and ''Emydoidea'') **Genus ''Glyptemys'' **Genus ''Terrapene'' **Genus ''Wilburemys'' sp. ''Wilburemys yakimensis'' *Subfamily Deirochelyinae **Genus ''Chrysemys'' **Genus ''Deirochelys'' **Genus ''Graptemys'' **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 Emydidae, Taxa named by Constantine Samuel Rafinesque Turtle families Cenomanian first appearances Cenomanian taxonomic families Turonian taxonomic families Coniacian taxonomic families Santonian taxonomic families Campanian taxonomic families Maastrichtian taxonomic families Danian taxonomic families Selandian taxonomic families Thanetian taxonomic families Ypresian taxonomic families Lutetian taxonomic families Bartonian taxonomic families Priabonian taxonomic families Rupelian taxonomic families Chattian taxonomic families Aquitanian taxonomic families Burdigalian taxonomic families Langhian taxonomic families Serravallian taxonomic families Tortonian taxonomic families Messinian taxonomic families Zanclean taxonomic families Piacenzian taxonomic families Gelasian taxonomic families Calabrian taxonomic families Ionian taxonomic families Tarantian taxonomic families Holocene taxonomic families Extant Cenomanian first appearances