''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. 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''. 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'', 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, taking advantage of the warm climate during the Eocene.

Species

The following three species are recognized as being valid. *'' Apalone ferox'' – 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'' – 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'' – 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'': A binomial authority 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) of Florida ( Alachua Formation). In addition, two other potential fossil species, generally placed in "''Trionyx''" ''sensu lato'', may belong to ''Apalone'': '' Apalone latus'' ( Gilmore, 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 of

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, 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 of

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.

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