Emydidae
Encyclopedia
Emydidae, commonly called the pond turtles or marsh turtles, is a family
of turtles. Previously, several species of Asian box turtle were classified in the family. However, revised taxonomy
has separated them to a different family. Now, Emydidae, with the exception of two species of pond turtle, is entirely a Western Hemisphere family. The family Emydidae includes close to 50 species
in 10 genera
.
) 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.
s, crustacean
s, and fish. In several species, there is a shift from carnivory in juveniles to herbivory in adults. Small mammals, especially raccoon
s, are responsible for the destruction of many Emydid nests. Members of all vertebrate classes predate eggs and hatchlings. The wide range of sizes in mature animals leads to an assortment of predators. While snapping turtle
s are responsible for predation in some smaller species (e.g., Clemmys muhlenbergii), they cannot eat larger species. Alligator
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 taxa (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.
and over-collection.
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 scute
s, 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
), while the former Batagurinae, today a separate family Geoemydidae
, 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. But with the Geoemydidae being split off it is better reinstated as its own family Platysternidae, though it seems very close to the emydid-geoemydid group.
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 relationship to the living genera are indeterminate.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of turtles. Previously, several species of Asian box turtle were classified in the family. However, revised taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
has separated them to a different family. Now, Emydidae, with the exception of two species of pond turtle, is entirely a Western Hemisphere family. The family Emydidae includes close to 50 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in 10 genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
.
Taxonomy
Description
The upper shell (carapaceCarapace
A carapace is a dorsal 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 underside is called the plastron.-Crustaceans:In crustaceans, the...
) 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.
Behavior
Food habits range from strictly carnivorous to strictly herbivorous. The carnivores feed on annelidAnnelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...
s, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, and fish. In several species, there is a shift from carnivory in juveniles to herbivory in adults. Small mammals, especially raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
s, are responsible for the destruction of many Emydid nests. Members of all vertebrate classes predate eggs and hatchlings. The wide range of sizes in mature animals leads to an assortment of predators. While snapping turtle
Snapping turtle
The common snapping turtle is a large freshwater turtle of the family Chelydridae. Its natural range extends from southeastern Canada, southwest to the edge of the Rocky Mountains, as far east as Nova Scotia and Florida and as far southwest as northeastern Mexico...
s are responsible for predation in some smaller species (e.g., Clemmys muhlenbergii), they cannot eat larger species. Alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....
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 taxa (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 to the Emydidae
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 degradationHabitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
and over-collection.
Systematics and evolution
Testudinoidea
Testudinoidea is a superfamily within the suborder Cryptodira of the order Testudines. It includes the families of pond turtles ; Asian turtles ; the Big-headed turtle and tortoises ....
. Shared features include a lack of inframarginal scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s, the shape and muscle attachment of the ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
, 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
Emys is a small genus of turtles. Its members are:* Emys orbicularis - European pond turtle* Emys trinacris - Sicilian pond turtle * Emys blandingii - Blanding's turtle * Emys marmorata - Western pond turtle- Sub-species :...
), while the former Batagurinae, today a separate family Geoemydidae
Geoemydidae
Geoemydidae is the largest and most diverse family in the order Testudines with about 70 species. It includes the Eurasian pond and river turtles and Neotropical wood turtles.-Characteristics:...
, contain Old World species (except Rhinoclemmys
Rhinoclemmys
Rhinoclemmys is a turtle genus in the family Geoemydidae . They are commonly known as the Neotropical wood turtles and are the only geoemydids known from the Americas...
). Osteological characters, such as the construction of the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
and articulations of the cervical vertebrae distinguish the two families.
The enigmatic Big-headed Turtle
Big-headed Turtle
The big-headed turtle is a species of turtle in the family Platysternidae.-Background:Previously considered a distinct family placed on occasion in "Kinosternoidea", it was later moved to the Emydidae. With the Geoemydidae being split off from these, it seems wisest to reinstate, at least for the...
(Platysternon megacephalum) was for some time considered a specialized but still very primitive early offshoot of the Emydidae. But with the Geoemydidae being split off it is better reinstated as its own family Platysternidae, though it seems very close to the emydid-geoemydid group.
Fossil record
Presumed emydids are well-represented in the fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record. Gyremys sectabilis and Clemmys backmani are both North American species that date from the Upper Cretaceous and Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
, respectively. These are the two oldest fossil species. Many other extinct species traditionally placed in the Emydidae are known from the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of North America, Asia and Europe, but the Old World taxa are likely to be more properly Geoemydidae
Geoemydidae
Geoemydidae is the largest and most diverse family in the order Testudines with about 70 species. It includes the Eurasian pond and river turtles and Neotropical wood turtles.-Characteristics:...
. The North American genus Palaeochelys and probably the trans-Atlantic Echmatemys too would seem to be Emydidae, but their precise relationship to the living genera are indeterminate.
Classification
The two subfamilies and 10 genera are arranged as follows:- Subfamily EmydinaeEmydinaeEmydinae is a subfamily of the turtles in the family Emydidae.-Subfamily classification:*Genus Clemmys*Genus Emys*Genus Glyptemys*Genus Terrapene...
- Genus ClemmysClemmysClemmys is a genus of turtle, consisting of one North American species, the spotted turtle ,"Clemmys guangxiensis" is a composite taxon described from specimens of Mauremys mutica and the natural hybrid "Mauremys" × iversoni .Until recently, the genus Clemmys consisted of four species Clemmys is a...
- Genus EmysEmysEmys is a small genus of turtles. Its members are:* Emys orbicularis - European pond turtle* Emys trinacris - Sicilian pond turtle * Emys blandingii - Blanding's turtle * Emys marmorata - Western pond turtle- Sub-species :...
(includes former genare Actinemys and Emydoidea) - Genus GlyptemysGlyptemysGlyptemys is a genus of turtle 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 currently has one member: the spotted turtle.Full grown, these...
- Genus Terrapene
- Genus Clemmys
- Subfamily DeirochelyinaeDeirochelyinaeThe Deirochelyinae are a subfamily of Emydidae. Consists of species native to North, and South America, some of which are frequently kept as pets...
- Genus Chrysemys
- Genus Deirochelys
- Genus GraptemysGraptemysGraptemys is a genus of turtles known commonly as map turtles or sometimes sawback turtles. They are aquatic, freshwater turtles that are found throughout the eastern half of the United States and northward into southern Canada. They superficially resemble many other species of aquatic turtle,...
- Genus Malaclemys
- Genus PseudemysPseudemysPseudemys is a genus of large, herbivorous, freshwater turtles of the eastern United States. They are often referred to as cooters, which stems from kuta, the word for turtle in the Bambara and Malinké languages, brought to America by African slaves....
- Genus TrachemysTrachemysTrachemys is a genus of turtles belonging to the family Emydidae.-Species:*Trachemys adiutrix - Maranhão slider*Trachemys callirostris - Colombian slider*Trachemys callirostris callirostris - Colombian slider...