View source for Spiny softshell turtle

{{Short description|Species of turtle}}
{{Use dmy dates|date=April 2017}}
{{Speciesbox
| image = Spiny softshell turtle (Apalone spinifera).jpg
| image_caption = 
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn">{{cite iucn |author=Doody, J.S. |author2=Gillingwater, S.D. |author3=Mali, I. |author4=Forstner, M.R.J. |author5=van Dijk, P.P. |author6=Rhodin, A.G.J. |year=2024 |title=''Apalone spinifera'' |volume=2024 |page=e.T163451A161722123 |doi=10.2305/IUCN.UK.2024-1.RLTS.T163451A161722123.en |access-date=22 June 2025}}</ref>
| genus = Apalone
| species = spinifera
| authority = ([[Charles Alexandre Lesueur|Lesueur]], 1827)<ref name="iucn" />
| subdivision_ranks = Subspecies
| subdivision = *[[Northern spiny softshell turtle]]<br>(''A. s. spinifera'')
*[[Gulf Coast spiny softshell turtle]]<br>(''A. s. aspera'')
*[[Black spiny softshell turtle]]<br>(''A. s. atra'')
*[[Texas spiny softshell turtle]]<br>(''A. s. emoryi'')
*[[Guadalupe spiny softshell turtle]]<br>(''A. s. guadalupensis'')
*[[Pallid spiny softshell turtle]]<br>(''A. s. pallida'')
| range_map = Apalone spinifera map.svg
| synonyms_ref = {{sfnp|Fritz|Havaš|2007|pp=306–310}}
| synonyms = {{collapsible list|bullets = true|title=<small>''[[Apalone spinifera spinifera]]''</small>
|''Trionyx nasica'' <br/>{{small|[[Constantine Samuel Rafinesque|Rafinesque]], 1822}} <br/>(''[[nomen suppressum]]'')
|''Trionyx spiniferus'' <br/>{{small|Lesueur, 1827}}
|''Apalone hudsonica'' <br/>{{small|Rafinesque, 1832}}
|''Gymnopus spiniferus'' <br/>{{small|— [[André Marie Constant Duméril|A.M.C. Duméril]] & [[Gabriel Bibron|Bibron]], 1835}}
|''Trionyx annulifer'' <br/>{{small|[[Prince Maximilian of Wied-Neuwied|Wied]], 1839}}
|''Tyrse argus'' <br/>{{small|[[John Edward Gray|Gray]], 1844}}
|''Trionyx annulatus'' <br/>{{small|Gray, 1856}}
|''Trionyx argus'' <br/>{{small|— Gray, 1856}}
|''Gymnopodus spiniferus'' <br/>{{small|— [[Auguste Duméril|A.H.A. Duméril]], 1856}}
|''Aspidonectes nuchalis'' <br/>{{small|[[Louis Agassiz|Agassiz]], 1857}}
|''Aspidonectes spinifer'' <br/>{{small|— Agassiz, 1857}}
|''Gymnopus spinifer'' <br/>{{small|— Agassiz, 1857}}
|''Trionyx spinifer'' <br/>{{small|— Agassiz, 1857}}
|''Gymnopus olivaceus'' <br/>{{small|Wied, 1865}}
|''Callinia spicifera'' <br/>{{small|Gray, 1869}}
|''Callinia spinifera'' <br/>{{small|— Gray, 1870}}
|''Platypeltis nuchalis'' <br/>{{small|— [[Georg Baur|Baur]], 1893}}
|''Platypeltis spinifer'' <br/>{{small|— Baur, 1893}}
|''Tyrse spinifera'' <br/>{{small|— [[Oliver Perry Hay|O.P. Hay]], 1904}}
|''Amyda spinifera'' <br/>{{small|— O.P. Hay, 1905}}
|''Platypeltis spinifera'' <br/>{{small|— O.P. Hay, 1907}}
|''Amyda spinifer'' <br/>{{small|— Potter, 1920}}
|''Amyda spinifera spinifera'' <br/>{{small|— [[Leonhard Stejneger|Stejneger]] & [[Thomas Barbour|T. Barbour]], 1939}}
|''Trionyx spinifera spinifera'' <br/>{{small|— [[Fred Ray Cagle|Cagle]], 1941}}
|''Amyda ferox spinifera'' <br/>{{small|— [[Wilfred T. Neill|Neill]], 1951}}
|''Trionyx ferox spinifera'' <br/>{{small|— [[Karl Patterson Schmidt|Schmidt]], 1953}}
|''Trionyx spinifer spinifer'' <br/>{{small|— Schwartz, 1956}}
|''Trionyx spiniferus spiniferus'' <br/>{{small|— [[Heinz Wermuth|Wermuth]] & [[Robert Mertens|Mertens]], 1961}}
|''Apalone spinifera'' <br/>{{small|— [[Peter Andre Meylan|Meylan]], 1987}}
|''Apalone spiniferus'' <br/>{{small|— Meylan & [[Robert G. Webb|Webb]], 1988}}
|''Apalone spinifera spinifera'' <br/>{{small|— [[Carl H. Ernst|Ernst]] & [[Roger W. Barbour|R. Barbour]], 1989}}
|''Apalone spinifera spinifera'' <br/>{{small|— Stubbs, 1989}}
|''Trionix spiniferus'' <br/>{{small|— Richard, 1999}}
}}
}}

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 (zoology)|specific name]], ''spinifera'' (spine-bearing), refer to the spiny, cone-like projections on the leading edge of the [[carapace]], which are not [[scute]]s (scales).

==Description==
The spiny softshell turtle's scientific name is very descriptive of the animal. ''Apalone'' comes from the Greek word ''apalos'', meaning soft or tender, and ''spinifera'' is of Latin origin; ''spina-'' referring to thorn or spine and ''-ifer'' meaning bearing. This species is a member of the family Trionychidae, and one of the most distinguishing features of members in this family is the presence of a leathery, moderately flexible carapace.<ref>{{cite journal|last1=Engstrom|first1=T.|title=Multiple data sets, high homoplasy, and the phylogeny of softshell turtles (Testudines: Trionychidae)|journal=Systematic Biology|date=2004|volume=53|issue=5|pages=693–710|doi=10.1080/10635150490503053|pmid=15545250|doi-access=free}}</ref> This is caused by loss of [[keratin]]ized scutes and some bony tissue loss. Spiny softshell turtles have webbed feet, each with three claws. Another distinguishing feature of softshell turtles is the presence of a fleshy, elongated nose.
[[File:Apalone spinifera 412346603.jpg|left|thumb|With a [[Red-eared slider|red eared slider]], [[Texas]]]]
The carapace (the upper part of the shell) ranges from brown or yellow-brown to olive in color, while the [[plastron]] (lower part of the shell) is lighter, usually white or yellow. Hatchlings usually have dark spots on the carapace, but as females age, they frequently become darker in color, or their carapace becomes splotched. Males tend to maintain the same coloration pattern from birth. Coloration also varies between each subspecies, and the exact coloration can also depend on an individual turtle's environment. Spiny softshell turtles are cryptically colored, meaning that their coloration helps them blend in with their surrounding environment.

Spiny softshell turtles also have pale lines bordered by black lines running from its head down the side of its neck. The carapace length ranges from {{cvt|18|to(-)|54|cm}}, with females growing larger than males. The namesake spines, also known as tubercles,<ref>{{Cite web |last1=Daniel |first1=W.M. |last2=Morningstar |first2=C.M. |last3=Somma |first3=L.A. |date=March 1, 2019 |title=Apalone Spinifera (Sesueur, 1827): U.S. Geological Survey, Nonindigenous Aquatic Species Database |url=https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1276 |access-date=March 3, 2025 |website=USGS}}</ref> are found along the anterior border of the carapace and are more commonly found in males. The variation in coloration, size, and spine presence indicates that this species exhibits [[sexual dimorphism]].

''A. spinifera'' has ridges on its nasal septum, making its nostrils c-shaped, unlike the nostrils of the similar species ''[[Apalone mutica|A. mutica]]'' which are round.<ref name=PC&C2016/>

==Distribution==
===Geographic range===
This species is the most widely distributed softshell turtle in North America.<ref>{{cite book |last1=Lazure |first1=Louis |last2=Pare |first2=Patrick |last3=Bouthillier |first3=Lyne |last4=Galois |first4=Patrick |title=Nesting biology and conservation of a northern population of spiny softshell turtles (Apalone spinifera). |date=2019 |publisher=Herpetological Conservation and Biology |edition=3 |url=https://www.amphibia-nature.org/download/pdf/Herpetological-Conservation-Biology_2019_14(3)659-667.pdf}}</ref> This could be due to habitat fragmentation caused by humans.<ref name=Galois/> The spiny softshell has a wide range, extending throughout much of the United States, as well as north into the [[Canada|Canadian]] provinces of [[Ontario]] and [[Quebec]], and south into the [[Mexico|Mexican]] states of [[Tamaulipas]], [[Nuevo León]], [[Coahuila]], and [[Chihuahua (state)|Chihuahua]].<ref name="iucn" /> Recently, the spiny softshell has expanded its geographic range ([[Introduced species|through human assistance]]) into New Jersey, Massachusetts, New Hampshire, [[Washington (state)|Washington]], and [[California]].<ref>{{Cite web |title=Spiny Softshell (''Apalone spinifera'') - Species Profile |url=https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1274 |access-date=2025-04-24 |website=USGS Nonindigenous Aquatic Species Database |language=en}}</ref> They were also recently discovered in Lake Champlain, contrary to historical records.<ref name=Galois>{{Cite journal |last1=Galois |first1=Patrick |last2=Léveillé |first2=Martin |last3=Bouthillier |first3=Lyne |last4=Daigle |first4=Claude |last5=Parren |first5=Steve |last6=Leveille |first6=Martin |date=September 2002 |title=Movement Patterns, Activity, and Home Range of the Eastern Spiny Softshell Turtle (''Apalone spinifera'') in Northern Lake Champlain, Quebec, Vermont |url=http://dx.doi.org/10.2307/1566184 |journal=Journal of Herpetology |volume=36 |issue=3 |pages=402 |doi=10.2307/1566184 |jstor=1566184 |issn=0022-1511|url-access=subscription }}</ref>

===Ecological range===
Spiny softshell turtles are often referred to as ecological generalists, meaning they are found in a wide variety of habitats.<ref>{{cite book |last1=Plummer |first1=Michael |last2=Mills |first2=Nathan |title=Growth and maturity of spiny softshell turtles (Apalone spinifera) in a small urban stream. |date=2015 |publisher=Herpetological Conservation and Biology |edition=2 |url=https://sites.harding.edu/plummer/pdf/plummermills2015.pdf}}</ref> The spiny softshell can be found in bodies of fresh water, including ponds, lakes, rivers, tributaries, bayous, oxbows, and streams.<ref>{{Cite web |title=NatureServe Explorer 2.0 |url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.100616/Apalone_spinifera |access-date=2025-04-24 |website=explorer.natureserve.org}}</ref> They can persist in more urban environments, as they are well-adapted to periodic habitat disturbances.<ref>{{Cite journal |last1=Plummer |first1=Michael V. |last2=Krementz |first2=David G. |last3=Powell |first3=Larkin A. |last4=Mills |first4=Nathan E. |date=September 2008 |title=Effects of Habitat Disturbance on Survival Rates of Softshell Turtles (''Apalone spinifera'') in an Urban Stream |url=http://www.bioone.org/doi/abs/10.1670/07-217.1 |journal=Journal of Herpetology |volume=42 |issue=3 |pages=555–563 |doi=10.1670/07-217.1 |bibcode=2008JHerp..42..555P |s2cid=51770178 |issn=0022-1511|url-access=subscription }}</ref> They inhabit shallow water less than {{cvt|1|m|abbr=on}} deep, but can also be found as much as {{cvt|10|m|abbr=on}} deep. When swimming, a study suggests that they get most of their thrusting power from their forelimbs as opposed to their hindlimbs, which is common in other species.<ref>{{cite journal|author=Cinnamon M. Pace|author2= Richard W. Blob|author3= Mark W. Westneat|title= Comparative kinematics of the forelimb during swimming in red-eared slider (''Trachemys scripta'') and spiny softshell (''Apalone spinifera'') turtles|journal= J Exp Biol |date=1 October 2001|volume= 204 |issue=19|pages= 3261–3271|doi=10.1242/jeb.204.19.3261|bibcode= 2001JExpB.204.3261P}}</ref> They can be found in areas with varying levels of vegetation, and although they are generally found in more slow-moving waters, this [[species abundance]] is greatest in waters with higher visibility and slower water velocity <ref>{{cite journal |last1=Barko |first1=Valerie |title=Midland smooth softshell (''Apalone mutica'') and Spiny Softshell (''Apalone spinifera'') Turtles in the Middle Mississippi River: Habitat Associations, Population Structure, and Implications for Conservation |date=2006 |volume=5 |journal=Chelonian Conservation and Biology |issue=2 |pages=225–31|doi=10.2744/1071-8443(2006)5[225:MSSAMA]2.0.CO;2 |s2cid=85571504 }}</ref> Spiny softshells prefer waters with sandy bottoms and clean, sandy banks. Sandy environments are important for nesting sites, proper juvenile growth and development, and camouflage.<ref>{{cite journal|last1=Plummer|first1=M.|title=Effects of habitat disturbance on survival rates of softshell turtles (''Apalone spinifera'') in an urban stream |journal=Journal of Herpetology|date=2008|volume=42|issue=3|pages=555–563|doi=10.1670/07-217.1|bibcode=2008JHerp..42..555P |s2cid=51770178|url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1426&context=natrespapers|url-access=subscription}}</ref>
Spiny softshells migrate between warm and cold seasons. In each season, turtles generally stay in a single zone, and they move more within their zone during warm months. The spiny softshell migrates between its zones and its average home range length is {{cvt|10.8|km|abbr=on}}.<ref>{{cite web |title=Environment and climate change |url=https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/recovery-strategies/spiny-softshell-2018.html |website=Canada.ca |date=21 December 2018 |publisher=/ Gouvernement du Canada}}</ref>

As far as home range, a study of the "eastern spiny" subspecies (which has the largest and most northern-reaching distribution) home range behavior found that turtles of northern [[Lake Champlain]] generally had two annual concentration areas for spring-summer and fall-winter, contributing to a large home range. Mean annual home range was also found, in the same study, to be over 10 times larger for female softshells compared to males. This study suggested that the large home range was due to [[habitat fragmentation]].<ref name= Galois/>

==Behavior==
===Diet===
Spiny softshell turtles feed on a variety of food items. They are primary consumers and feed on invertebrates (crayfish and aquatic insects), fish,<ref>{{cite web |last1=Anderson |first1=Noah |title=Biomechanics of Feeding and Neck Motion in the Softshell Turtle, ''Apalone spinifera'', Rafinesque |url=https://www.proquest.com/docview/305062583 |via=ProQuest |id={{ProQuest|305062583}} }}</ref> algal stocks and other plant material, and [[mussels]]. They are generally observed as benthic feeders; they can either actively hunt prey or bury themselves in the sand and wait to ambush prey.<ref>{{cite journal |last1=Williams |first1=T. |title=The niches of two sympatric softshell turtles, ''Trionyx muticus'' and ''Trionyx spiniferus'', in Iowa |journal=Journal of Herpetology |date=1981 |volume=15 |issue=3 |pages=303–308 |doi=10.2307/1563433 |jstor=1563433}}</ref>

Some evidence suggests that spiny softshell turtles exhibit a nuclear-follower foraging association with fish. A study that took place in an urban drainage canal in [[Louisiana]] found that when foraging, spiny softshell turtles were observed moving along the creek bottom thrusting their probosces into the substrate which then allowed fish to enter the suspended sediment and capture prey otherwise unavailable to the fish. The fish benefit from increased foraging success, while few benefits accrue to the foraging turtles.<ref>{{Cite journal |last1=Platt |first1=Steven G. |last2=Rainwater |first2=Thomas R. |date=November 2021 |title=Observations of a Nuclear–follower Foraging Association between Spiny Softshell Turtles (Apalone spinifera) and Fish in an Urban Drainage Canal in Louisiana |journal=Southeastern Naturalist |volume=20 |issue=4 |pages=N108–N114 |doi=10.1656/058.020.0406 |s2cid=244674573 |issn=1528-7092}}</ref>

===Reproduction===
[[File:Softshell turtle laying eggs.jpg|thumb|Laying eggs at Los Angeles' [[Baldwin Lake (Los Angeles County, California)|Baldwin Lake]], a part of the species' non-native introduced range]]
[[File:Spiny Softshell Turtles (Apalone spinifera) juvenile (9186492956).jpg|thumb|Juvenile spiny softshell turtles]]

Spiny softshells begin mating between ages 8 and 10. A large female turtle may live up to 50 years. The turtles mate in mid-to-late spring in deep water. The male will nudge the female's head while swimming and wave their feet in front of her face,<ref>{{Cite web |last1=Lovell |first1=Mailing Address: Bighorn Canyon National Recreation Area South District Visitor Center 20 US Hwy 14A |last2=Lovell |first2=WY 82431 Phone: 307 548-5406548-5406 is the South District in |last3=Us |first3=WY Contact |title=Spiny Softshell Turtle - Bighorn Canyon National Recreation Area (U.S. National Park Service) |url=https://www.nps.gov/bica/learn/nature/spiny-softshell-turtle.htm |access-date=2025-04-24 |website=www.nps.gov |language=en}}</ref> and if she chooses to mate, the male will swim above the female without clasping her with his claws (unlike other turtles). Prior to nesting, the females have been observed to have a 3 stage activity pattern throughout the day. The females start the day by basking and moving around an area, then they spend a majority of their afternoon swimming in a new area, and finally they would stop and search for an ideal nesting spot.<ref>{{Cite journal |last1=Daigle |first1=Claude |last2=Galois |first2=Patrick |last3=Chagnon |first3=Yves |date=2002 |title=Nesting activities of an Eastern Spiny Softshell Turtle, Apalone spinifera |journal=The Canadian Field-Naturalist |volume=116 |issue=1 |pages=104–107 |doi=10.5962/p.363405|doi-access=free }}</ref> A few months later, the female turtle quickly lays her [[egg (biology)|eggs]] along a sunny [[sandbar]] or gravel bank in a flask-shaped cavity she has dug close to the water. This nesting behavior typically begins around July with the females leaving the water and probing the ground with her snout to find the spot to lay her eggs.<ref>{{cite journal |last1=Tornabene |last2=Bramblett |first2=R.G |last3=Zale |first3=A.V |last4=Leathe |first4=S.A |title=Factors Affecting Nesting Ecology of Apalone spinifera in a Northwestern Great Plains River of the United States |journal=Chelonian Conservation and Biology |date=2018 |volume=17 |issue=1 |pages=63–77 |doi=10.2744/CCB-1298.1|bibcode=2018CConB..17...63T |s2cid=90056294 }}</ref> The turtle nests more than once during a single season. She can lay between 9 and 38 round, [[calcareous]]-shelled eggs. The eggs are laid around July and September, and they hatch in the spring. Larger bodied females have been found to lay a second clutch in late June or July.<ref>{{cite journal |author=Robinson, Keith M.|author2= George G. Murphy|title=The Reproductive Cycle of the Eastern Spiny Softshell Turtle (''Trionyx spiniferus spiniferus'')|journal= Herpetologica|volume= 34|issue= 2|year= 1978 |pages=37–140|jstor=3891665}}</ref> In studies observing nesting behavior, it has been found that the females are more likely to lay eggs on days where there is a small difference between the air and water temperatures.<ref>{{cite journal |last1=Lazure |first1=L. |last2=Pare |first2=P. |last3=Bouthillier |first3=L. |last4=Galois |first4=P. |date=2019 |title=Nesting biology and conservation of a northern population of spiny softshell turtles (''Apalone spinifera'') |journal=Herpetological Conservation and Biology |volume=14 |issue=3 |pages=659–667}}</ref> Unlike in some other turtles, in the spiny softshell turtle, the sex of the hatchlings is not determined by [[Temperature-dependent sex determination|temperature variations]]; it is determined by [[ZW sex-determination system|genetics]].<ref>{{cite journal |last1=Greenbaum |first1=Eli |last2=Carr |first2=John L. |year=2001 |title=Sexual Differentiation in the Spiny Softshell Turtle ''(Apalone spinifera)'', a Species With Genetic Sex Determination |journal=Journal of Experimental Biology |volume=290 |issue=2| pages=190–200 |doi=10.1002/jez.1049| pmid=11471149 |bibcode=2001JEZ...290..190G}}</ref>

Late-term embryos and hatchlings of spiny softshell turtles have been recently found to make various click- and chirp-type sounds before emergence onto the surface. The function of these sounds is currently unknown.<ref>{{cite journal|author=Geller, G.A. |author2= G.S. Casper|year= 2023|title= Sound production by late-term embryos and hatchlings of the Spiny Softshell Turtle, ''Apalone spinifera'' (LeSueur, 1827) before nest exit |journal=Herpetology Notes |volume=16|pages=483–491}}</ref>

===Respiration===
Spiny softshell turtles are bimodal breathers, meaning they have the ability (to some degree) to perform oxygen and carbon dioxide exchange by breathing air or while breathing underwater. A variety of factors allow for these turtles to perform respiration underwater. They have an increase of cutaneous surface area and blood flow, reduction in lung size, and increase of respiratory [[epithelium]] in the [[cloaca]] and [[wiktionary:buccopharynx|buccopharynx]]. This turtle is also known to utilize [[cutaneous respiration]] as well.<ref name="jstor.org">{{cite journal|author=Plummer, Michael V.|author2= Caleb S. O’Neal|title=Aerobic Pushups: Cutaneous Ventilation in Overwintering Smooth Softshell Turtles, ''Apalone mutica''|journal= Journal of Herpetology|volume= 53|issue= 1|year= 2019|pages= 27–31|doi= 10.1670/18-038|jstor=26908244}}</ref> Spiny softshell turtles are more dependent on underwater respiration than other freshwater species. This has led to their low tolerance of hypoxic waters; this becomes especially important during times of hibernation, when these turtles must choose hibernacula that are unlikely to become hypoxic. Underwater dormancy can last up to six months.<ref name="jstor.org"/> They are known as an [[Anoxic waters|anoxia]]-intolerant species because of their dependency on underwater respiration. Other turtle species are more adapted to variation in oxygen levels but spiny softshell turtles are not able to regulate it as well, especially during hibernation periods. This makes choosing hibernacula very important to their over-winter survival. While they are susceptible to anoxia, they have the ability to maintain their metabolism completely via aerobic means which gives them a slight advantage when compared to other hibernating aquatic turtles during winter.<ref>{{cite journal|author=Reese, S. A. |author2=Jackson, D. C.|author3= Ultsch, G. R. |year=2003|title= Hibernation in freshwater turtles: softshell turtles (''Apalone spinifera'') are the most intolerant of anoxia among North American species|journal= Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology|volume= 173|issue=3|pages= 263–268|doi=10.1007/s00360-003-0332-1|pmid=12687397 }}</ref>

==Conservation==
Overall, the spiny softshell turtle is widespread, common and not threatened,<ref name="iucn"/> but some local populations are under pressure. In Canada, which is at the northern margin of its range and where the species is quite local, it is considered endangered.<ref>{{cite web| title=Spiny Softshell | url=https://ontarionature.org/programs/community-science/reptile-amphibian-atlas/spiny-softshell/ | publisher=OntarioNature | access-date=14 October 2023}}</ref> The very rare [[black spiny softshell turtle]], a subspecies found only in Mexico's [[Cuatro Ciénegas Basin]], is considered [[critically endangered]].<ref>{{cite iucn|author=Tortoise & Freshwater Turtle Specialist Group|year=2016|title=''Apalone spinifera'' ssp. ''atra''|page=e.T1820A97408016|doi=10.2305/IUCN.UK.2016-1.RLTS.T1820A97408016.en|access-date=14 October 2023}}</ref>

==Taxonomy==
The [[species]] was first described by [[Charles Alexandre Lesueur]] in 1827.<ref name="iucn" /> It has been redescribed numerous times, leading to some confusion in its [[Taxonomy (biology)|taxonomy]].<ref>[http://www.tortoise.org/archives/apalone.html California Turtle & Tortoise Club: Softshell Turtles].</ref>

===Subspecies===
{{multiple image
| direction         = vertical
| image1            = Eastern Spiny Softshell Turtle (Apalone spinifera spinifera) - Flickr - 2ndPeter.jpg
| image2            = Apalone spinifera, Colorado Co., Texas; 28 June 2014.jpg
| width1            = 220
| width2            = 220
| footer            = ''[[Northern spiny softshell turtle|A. s. spinifera]]'' (above) and ''[[Pallid spiny softshell turtle|A. s. pallida]]'' (below). Both can vary considerably in coloration and markings.
}}

The recognized [[subspecies]] differ in the markings on their carapaces, on the sides of their heads, and on their feet, although there are also considerable individual (not related to subspecies) variations in the appearance. Their markings, which are distinct as hatchlings, fade as the turtles grow larger. Adult females of the various subspecies, which grow larger than males, are not easily distinguishable from one another, and sometimes can only be assigned to a particular subspecies based on geography.<ref>{{cite book|author=Conant R |year=1975|title=A Field Guide to Reptiles and Amphibians of Eastern and Central North America|edition= Second |location=Boston|publisher= Houghton Mifflin|chapter=Softshell Turtles: Family Trionychidae|pages= 76–77}}</ref><ref name=PC&C2016>{{cite book |last1=Powell |first1=Robert |author1-link=Robert Powell (herpetologist) |last2=Conant |first2=Roger |author2-link=Roger Conant (herpetologist) |last3=Collins |first3=Joseph T. |author3-link=Joseph T. Collins |title=A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition |date=2016 |location=Boston and New York |publisher=Houghton Mifflin Harcourt |isbn=978-0-544-12997-9}} xiv + 494 pp., 47 plates, 207 figures. (''Apalone spinifera'', pp. 232–233 + Plates 20, 22 + Figures 85, 105, 106).</ref>

Six subspecies of ''A.&nbsp;spinifera'' are recognized, including the [[nominate subspecies]]:<ref>{{ITIS|id=208680|taxon=''Apalone spinifera''|access-date=31 May 2012}}</ref>

*[[Northern spiny softshell turtle]] or eastern spiny softshell,<ref>{{EMBL species|genus=Apalone|species=spinifera}}.</ref> ''A. s. spinifera'' ([[Charles Alexandre Lesueur|Lesueur]], 1827)<ref name="iucn" />
*[[Gulf Coast spiny softshell turtle]], ''A. s. aspera'' ([[Louis Agassiz|Agassiz]], 1857)<ref name="iucn" />
*[[Black spiny softshell turtle]] or Cuatro Cienegas softshell turtle, ''A. s. atra'' ([[Robert G. Webb|Webb]] & [[John M. Legler|Legler]], 1960)<ref name="iucn" />
*[[Texas spiny softshell turtle]], ''A. s. emoryi'' ([[Louis Agassiz|Agassiz]], 1857)<ref name="iucn" />
*[[Guadalupe spiny softshell turtle]], ''A. s. guadalupensis'' ([[Robert G. Webb|Webb]], 1962)<ref name="iucn" />
*[[Pallid spiny softshell turtle]], ''A. s. pallida'' ([[Robert G. Webb|Webb]], 1962)<ref name="iucn" />

A previously recognized subspecies, ''[[Apalone spinifera hartwegi]]'' ([[Roger Conant (herpetologist)|Conant]] & [[:fr:Coleman Jett Goin|Goin]], 1941), has been synonymized to ''A.&nbsp;s. spinifera'' as of 2011.<ref name="iucn" />

==Genomics==
A rough-draft assembly of the ''A.&nbsp;spinifera aspera'' genome was completed in 2013 by the [[McDonnell Genome Institute|Genome Institute]] at [[Washington University in St. Louis]]. The assembly ASM38561v1 can be accessed via its Genbank accession ID APJP00000000.1 [https://www.ncbi.nlm.nih.gov/nuccore/APJP00000000.1]

==References==
{{Reflist}}

;Bibliography
*{{cite book |chapter=Turtles of the world, 2011 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status |title=Conservation Biology of Freshwater Turtles and Tortoises |series=Chelonian Research Monographs |volume=5 |date=2011-12-31 |last1=van Dijk|first1=Peter Paul |last2=Iverson|first2=John B. |last3=Shaffer|first3=H. Bradly |last4=Bour|first4=Roger |last5=Rhodin|first5=Anders G. J. |url=http://www.iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_000_checklist_v4_2011.pdf |ref={{harvid|van Dijk et al.|2011}}}}
*{{cite journal | journal = Vertebrate Zoology | title = Checklist of Chelonians of the World | year = 2007 | first1 = Uwe | last1 = Fritz | last2 = Havaš |first2 = Peter | volume = 57 | issue = 2 | pages = 149–368 | doi = 10.3897/vz.57.e30895 | s2cid = 87809001 | doi-access = free }}

==Further reading==
*[[John L. Behler|Behler JL]], King FW (1979). ''The Audubon Society Field Guide to North American Reptiles and Amphibians''. New York: Alfred A. Knopf. 743 pp. {{ISBN|0-394-50824-6}}. (''Trionyx spiniferus'', pp.&nbsp;485–486 + Plates 270, 271).
*[[George Albert Boulenger|Boulenger GA]] (1889). ''Catalogue of the Chelonians, Rhynchocephalians, and Crocodiles in the British Museum (Natural History). New Edition.'' London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). x + 311 pp. + Plates I-III. (''Trionyx spinifer'', pp.&nbsp;259–260).
*[[Charles Alexandre Lesueur|Lesueur CA]] (1827). "''Note sur deux espèces de tortues, du genre Trionyx de M[onsieur]. Geoffroy-Saint-Hilaire'' ". ''Mémoires du Muséum d'Histoire Naturelle, Paris'' '''15''': 257-268 + Plates 6–7. (''Trionyx spiniferus'', new species, pp.&nbsp;258–263 + Plate 6). (in French).
*[[Hobart Muir Smith|Smith HM]], Brodie ED Jr (1982). ''Reptiles of North America: A Guide to Field Identification''. New York: Golden Press. 240 pp. {{ISBN|0-307-13666-3}}. (''Trionyx spiniferus'', pp.&nbsp;31–33).
*[[Leonhard Stejneger|Stejneger L]], [[Thomas Barbour|Barbour T]] (1917). ''A Check List of North American Amphibians and Reptiles''. Cambridge Massachusetts: Harvard University Press. 125 pp. (''Amyda spinifera'', p.&nbsp;125).
*{{Cite journal |last1=Kominek |first1=Emma |last2=Cornies |first2=Olivia |last3=McCurdy-Adams |first3=Hannah |last4=Mooers |first4=Arne Ø |date=2023 |title=Evolutionary isolation of Canadian terrestrial vertebrate species |url=https://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/2673 |journal=The Canadian Field-Naturalist |language=en |volume=137 |issue=4 |pages=367–380 |doi=10.22621/cfn.v137i4.2673 |issn=0008-3550|url-access=subscription |doi-access=free }}

==External links==
* [https://archive.org/stream/descriptivecatal00theo#page/n305/mode/2up Drawing of skull of Spiny Softshell Turtle]

{{Trionychidae}}
{{Taxonbar|from=Q650232}}
{{Authority control}}

[[Category:Apalone]]
[[Category:Turtles of North America]]
[[Category:Reptiles of the United States]]
[[Category:Reptiles of Mexico]]
[[Category:Fauna of the Eastern United States]]
[[Category:Reptiles of Ontario]]
[[Category:Reptiles described in 1827]]
[[Category:Taxa named by Charles Alexandre Lesueur]]
[[Category:Fauna of the Northwestern United States]]