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Emydidae

(Family)

Overview

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Emydidae, commonly called the pond turtles or marsh turtles,1] is a family of turtles.[3] 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.[4]

Description

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This shaded bog turtle specimen is resting in the palm of a person's hand, highlighting its petite size.
This bog turtle displays the keeled carapace, large bridge, and small head found in most emydids.

The upper shell (carapace) 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.[1]

The limbs of these turtles are adapted for swimming, with every member having some level of toe webbing.[1]

Behavior

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Food habits range from strictly carnivorous to strictly herbivorous. The carnivores feed on annelids, crustaceans, and fish. In several species, there is a shift from carnivory in juveniles to herbivory in adults. Small mammals, especially raccoons, 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 turtles are responsible for predation in some smaller species (e.g., Clemmys 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 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

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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 degrad ation and over-collection.

Systematics and evolution

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Echmatemys wyomingensis

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), 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.

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 relationship to the living genera are indeterminate.

Classification

The two subfamilies and 10 genera are arranged as follows:[4]

per shell (carapace) 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.[1]

The limbs of these turtles are adapted for swimming, with every member having some level of toe webbing.[1]

Behavior

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Food habits range from strictly carnivorous to strictly herbivorous. The carnivores feed on annelids, crustaceans, and fish. In several species, there is a shift from carnivory in juveniles to herbivory in adults. Small mammals, especially raccoons, are responsible for the destruction of many Emydid nests. Members of all vertebrate classe s predate eggs and hatchlings. 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., Clemmys 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 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

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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 degradation and over-collection.

Systematics and evolution

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Echmatemys wyomingensis

The Emydidae are most closely related to the tortoises (Testudinidae) and are included along with that family in the Test udinoidea. 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), 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.

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 relationship to the living genera are indeterminate.

Classification

The two subfamilies and 10 genera are arranged as follows:[4]

References

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  1. ^ a b c d Ernst 1994, p. 203
  2. ^ a < sup>b Rhodin 2010, p. 000.99
  3. ^ EMYSystem Family Page: Emydidae (Pond Turtles)
  4. ^ a b Rhodin 2010, pp. 000.99-000.107

External links

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Taxonomy

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The Family Emydidae is a member of the Superfamily Testudinoidea. Here is the complete "parentage" of Emydidae:

The Family Emydidae is further organized into finer groupings including:

Genera

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Actinemys

[more]

Batagur

The Batagur, also called giant river turtle or mangrove terrapin (Batagur baska) is a species of riverine . It is one of the most critically-endangered turtle species according to a 2003 assessment by the IUCN. Batagur baska is a rare and endangered Asian river terrapin also called the "Royal Turtle" in Cambodia because its eggs were a royal delicacy. [more]

Chrysemys

The painted turtle (Chrysemys picta) is the most widespread native turtle of North America. It lives in slow-moving fresh waters, from southern Canada to Louisiana and northern Mexico, and from the Atlantic to the Pacific. The turtle is the only species of the genus Chrysemys, which is part of the pond turtle family Emydidae. Fossils show that the painted turtle existed 15 million years ago, but four regionally based subspecies (the eastern, midland, southern, and western) evolved during the last ice age. [more]

Clemmys

Clemmys is a genus of turtle, consisting of one North American species, the spotted turtle (C. guttata), [more]

Cuora

Asian box turtles are turtles of the genus Cuora in the family Geoemydidae comprising 10?11 species with about the same number of subspecies. The keeled box turtle (Pyxidea mouhotii / Cuora mouhotii) is often included in this genus but is also often placed in its own genus (Pyxidea). The genus occurs from Assam throughout Southeast Asia and central to southern China northeastwards to Japan, and southeastwards to the borders of the Wallacea and onto Indonesia and the Philippines. [more]

Deirochelys

[more]

Dierochelys

[more]

Echmatemys

Emydoidea

Blanding's turtle (Emys blandingii or Emydoidea blandingii) is a semi-aquatic turtle of the family Emydidae. It is considered to be an endangered species throughout much of its range. [more]

Emys

Emys is a small of turtles. Its members are: [more]

Geoclemmys

Geomyda

[more]

Glyptemys

[more]

Graptemys

Graptemys 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, including sliders (Trachemys) and cooters (Pseudemys). However, they are distinguished by a keel that runs the length of the center of their carapace; they also typically grow to a smaller size at maturity. They are given the name map turtle due to the map-like markings on the carapace. Average life expectancy of map turtles ranges from 15 to 20 years. [more]

Homopus

Homopus is a genus of in the Testudinidae family. It contains the following species: [more]

Kinixys

Kinixys is a genus of in the Testudinidae family. It contains the following species: [more]

Malaclemmys

Malaclemys

The diamondback terrapin (Malaclemys terrapin) or simply terrapin, is a species of turtle native to the brackish coastal swamps of the eastern and southern United States. It belongs to the monotypic genus, Malaclemys.  It has one of the largest ranges of all  turtles in North America, stretching from the Florida Keys to Cape Cod. [more]

Manouria

Manouria is a genus of in the Testudinidae family. It contains the following species: [more]

Mauremys

Mauremys is a genus of turtle in the family Geoemydidae (formerly called Bataguridae). Ocadia and Chinemys are included here by some scientists, but not by the majority nor by hobbyists. [more]

Melanochelys

[more]

Psammobates

[more]

Pseudemys

Pseudemys is a of pond turtles also known as Cooter Turtles, especially in the state of Florida. (The word "cooter" may be used to refer to snapping turtles of the Chelydridae family elsewhere in the southeastern United States.) Cooter stems from kuta, the word for turtle in the Bambara and Malinké languages, brought to America by African slaves. [more]

Pyxis

A Genus in the Kingdom Animalia. [more]

Rhinoclemmys

Rhinoclemmys is a genus in the family Geoemydidae (formerly Bataguridae). They are commonly known as the Neotropical wood turtles and are the only geoemydids known from the Americas. As such, they have adapted to a wide range of habitats, which is reflected in the species' common names. [more]

Terrapene

The box turtle (Terrapene), or box tortoise is a genus of turtle native to North America (United States and Mexico). The 12 taxa which are distinguished in the genus are distributed over four species. It is largely characterized by having a domed shell, which is hinged at the bottom, allowing the animal to close its shell tightly to escape predators. Box turtles have become popular pets, although their needs in captivity are complex. [more]

Testudo

[more]

Trachemys

Trachemys is a of water turtles found in North, Central, and South America. They are commonly known as "Sliders". It includes the Red-eared slider (Trachemys scripta elegans), which is the most common turtle kept as a pet. [more]

At least 44 species and subspecies belong to the Genus Trachemys .

More info about the Genus Trachemys may be found here.

References

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  1. ^ a b c d Ernst 1994, p. 203
  2. ^ a b Rhodin 2010, p. 000.99
  3. ^ EMYSystem Family Page: Emydidae (Pond Turtles)
  4. ^ a b Rhodin 2010, pp. 000.99-000.107

Sources

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Last Revised: August 24, 2012
2012/08/24 13:31:06