''Apalone'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 ...

s in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Trionychidae Trionychidae is a family of turtles, commonly known as softshell turtles or simply softshells. The family was described by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to li ...

. The three

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), ...

of ''Apalone'' are native to freshwater habitats in North America; they are the only living

softshell turtle Trionychidae is a family of turtles, commonly known as softshell turtles or simply softshells. The family was described by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to li ...

s from the Americas (other American softshell turtles are only known from fossil remains).

Geographic range

Most ''Apalone'' species are restricted to the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, though the range of the spiny softshell, ''A. spinifera'', extends into southern

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

and northern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. Fossil evidence suggests that ''Apalone'' may have reached as far south as

Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...

during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58

Taxonomy

''Apalone'' is a fairly new classification, resurrected by Meylan in 1987, assigned to North American species of the genus ''

Trionyx ''Trionyx'' is a genus of softshell turtles belonging to the family Trionychidae. In the past many species in the family were classified in this genus, but today '' T. triunguis'', the African or Nile softshell turtle, is the only extant softshel ...

''. They are still listed as ''Trionyx'' in some texts. (''Trionyx'' now refers specifically to certain softshell species found mainly in Africa.) Molecular phylogenetic studies generally suggest that ''Apalone'' is most closely related to the highly endangered Asian genus ''

Rafetus ''Rafetus'' is a genus of highly endangered softshell turtles in the family Trionychidae. It is a genus of large turtles which are found in freshwater habitats in Eurasia. Taxonomy Evolution Phylogenetic evidence largely suggests that ''Rafe ...

'', with the two genera most likely diverging during the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

. The ancestral ''Apalone'' most likely crossed from Asia into North America via

Beringia Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 70th parallel north, 72° north latitude in the Chukchi Sea; and on the south ...

, taking advantage of the warm climate during the Eocene.

Species

The following three species are recognized as being valid. *''

Apalone ferox The Florida softshell turtle (''Apalone ferox'') is a species of turtle in the family Trionychidae. The species is native to the Southeastern United States. Rafinesque, Constantine S. "12. Description of two new genera of Soft Shell Turtles of No ...

'' – Florida softshell turtle -

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, and

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

*''

Apalone mutica The smooth softshell turtle (''Apalone mutica'') is a species of North American softshell turtle in the family Trionychidae. This freshwater species is endemic to the United States, where it inhabits the Mississippi River system, along with other ...

'' – smooth softshell turtle -

, east of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

*''

Apalone spinifera The spiny softshell turtle (''Apalone spinifera'') is a species of softshell turtle, one of the largest freshwater turtle species in North America. Both the common name, spiny softshell, and the specific name, ''spinifera'' (spine-bearing), refe ...

'' – spiny softshell turtle -

(southern

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

and

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

), most of the United States, and northeastern

. ''

Nota bene ( ; plural: ) is the Latin language, Latin phrase meaning ''note well''. In manuscripts, ''nota bene'' is abbreviated in upper-case as NB and N.B., and in lower-case as n.b. and nb; the editorial usages of ''nota bene'' and ''notate bene'' fi ...

'': A

binomial authority In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...

in parentheses indicates that the species was originally described in a genus other than ''Apalone''.

Fossil taxa

One definitive fossil species is also known, '' A. amorense'' Valdes, Bourque & Vitek, 2017 from the late

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

(late

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 ...

) of Florida (

Alachua Formation The Alachua Formation is a Miocene Formation (stratigraphy), geologic formation in Florida. The claystones, sandstones and phosphorites of the formation preserve many fossils of mammals, birds, reptiles and fish, among others megalodon. Fossil c ...

). In addition, two other potential fossil species, generally placed in "''Trionyx''" ''sensu lato'', may belong to ''Apalone'': '' Apalone latus'' (

Gilmore Gilmore or Gillmore may refer to: *Gilmore (surname) Places Australia *Gilmore, Australian Capital Territory, a suburb in the Canberra district of Tuggeranong * Gilmore Avenue, a road in southern Perth, Western Australia *Division of Gilmore, a ...

, 1919) from the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

-aged

Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

, Canada and '' Apalone leucopotamica'' (

Cope A cope ( ("rain coat") or ("cape")) is a liturgical long mantle or cloak, open at the front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A cope may be worn by any rank of the Catholic or Anglican clerg ...

, 1891) from the late

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

-aged

Cypress Hills Formation The Cypress Hills Formation is a stratigraphic unit of middle Eocene to early Miocene ageLeckie, D.A. and Cheel, R.J. 1989. The Cypress Hills Formation – A semi-arid braid plain deposit resulting from intrusive uplift. Canadian Journal of Earth ...

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

. These two species are much older than any other remains assigned to ''Apalone'', and even predate the presumed divergence of the genus based on molecular phylogenies. However, none of these have been rigorously tested, and the placement of these genera within ''Apalone'' may just be a result of

homoplasy Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize ...

Sexual dimorphism

Turtles of the genus ''Apalone'' exhibit marked

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. In carapace length, females grow to about twice the size of males. In males, the claws on the front feet are longer than those on the back feet, but in females, the claws on the back feet are longer. In males, the stout tail extends well beyond the posterior edge of the carapace, but in females, the relatively thinner tail barely reaches the edge of the carapace. Smith HM, Brodie ED Jr (1982). ''Reptiles of North America: A Guide to Field Identification.'' New York: Golden Press. 240 pp. . (SOFTSHELL TURTLES—family Trionychidae, p. 30).

Behavior

''Apalone'' turtles are fast swimmers that chase down their prey in water. They feed mainly on fish. They also like the comfort of sand as their bedding.

References

External links

*
Tortoise.org ''Apalone'' entrySpiny Softshell Turtle - ''Apalone spinifera''
Species account from the Iowa Reptile and Amphibian Field Guide {{Authority control Turtle genera Turtles of North America Trionychinae Taxa named by Constantine Samuel Rafinesque