''Deirochelys'' is a genus of freshwater

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

in the family

Emydidae Emydidae (Latin (freshwater tortoise) + Ancient Greek (, "appearance, resemblance")) is a family of testudines (turtles) that includes close to 50 species in 10 genera. Members of this family are commonly called terrapins, pond turtles, or mar ...

, the pond and marsh turtles. It contains one

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, the

chicken turtle The chicken turtle (''Deirochelys reticularia'') is a turtle native to the southeastern United States. It is the Monotypic taxon, only extant member of the genus ''Deirochelys'' and is a member of the freshwater marsh turtle family Emydidae. The ...

(''Deirochelys reticularia''), which is native to the

southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...

. A second

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

member, ''

Deirochelys carri ''Deirochelys'' is a genus of freshwater turtle in the family Emydidae, the pond and marsh turtles. It contains one extant species, the chicken turtle (''Deirochelys reticularia''), which is native to the southeastern United States. A second exti ...

'', is known from a fossil found in

Alachua County, Florida Alachua County ( ) is a county in the north central portion of the U.S. state of Florida. As of the 2020 census, the population was 278,468. The county seat is Gainesville, the home of the University of Florida. History Prehistory and ear ...

. The genus was first described by

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

in 1857, and its name is derived from the

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

words for "neck" (''deirḗ'') and "tortoise" (''khélūs''), referring to the particularly long necks of these turtles.

Evolution

Like other emydids (members of the family Emydidae), ''Deirochelys''

karyotype A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by de ...

consists of 2N=50

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s. A 1996 study of various turtles'

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

supported the partition of Emydidae into two subfamilies,

Emydinae The Emydinae are a subfamily of turtles in the family Emydidae Emydidae (Latin (freshwater tortoise) + Ancient Greek (, "appearance, resemblance")) is a family of testudines (turtles) that includes close to 50 species in 10 genera. Members ...

and

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 ...

, with ''Deirochelys'' placed within the latter. ''Deirochelys'' was reported to be the

sister genus In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to the rest of the subfamily, meaning it shares a common ancestor with the ancestor of all the other genera in Deirochelyinae. Alternative analysis by Stephens and Wiens found that under certain analyses ''Deirochelys'' could instead be described as a sister taxon to Emydinae or indeed to the family Emydidae itself. The authors attributed this confusion to

long-branch attraction In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lin ...

and concluded that ''Deirochelys'' did indeed sit within Deirochelyinae. Spinks et al. (2009) also found ''Deirochelys'' to be a sister to Emydidae under

maximum parsimony In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or minimizes the cost of differentially weighted charact ...

. It has been proposed that ''Deirochelys'' and the painted turtles ''

Chrysemys ''Chrysemys'' is a genus of turtles in the family Emydidae. They are found throughout most of North America. Reproduction Chrysemys have temperature dependent sex determination. During egg incubation, lower temperatures produce males while higher ...

'' are among the most

ancient Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient h ...

emydids, having diverged from the rest of the emydids more than 24.4 million years ago. The genus ''Deirochelys'' itself is thought to have evolved before the end of the

Clarendonian The Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 13,600,000 to 9,000,000 years BP, a period of . It is us ...

, over 10.3 million years ago.

Species

There are two currently accepted species: * ''

Deirochelys reticularia The chicken turtle (''Deirochelys reticularia'') is a turtle native to the southeastern United States. It is the only extant member of the genus ''Deirochelys'' and is a member of the freshwater marsh turtle family Emydidae. The chicken turtle' ...

'' (chicken turtle) * ''

'' A possible third species, ''D.floridana'', was described by

Oliver Perry Hay Oliver Perry Hay (May 22, 1846 – November 2, 1930) was an American herpetologist, ichthyologist, and paleontologist. Hay was born in Jefferson County, Indiana, to Robert and Margaret Hay. In 1870, Hay graduated with a bachelor of arts from ...

in 1908 from a fossil specimen. In 1964, C.G. Jackson determined the specimen to instead be ''D.reticularia'', but in 1974 he reassigned it to the genus ''Chrysemys''. Jasinski (2018) reasserted that this turtle did indeed represent a separate species of ''Deirochelys''.

References

{{Taxonbar, from=Q14566118 Turtle genera Reptile genera with one living species Taxa named by Louis Agassiz Deirochelys