''Sternotherus'' is a genus of turtles 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 ...

Kinosternidae The Kinosternidae are a family of mostly small turtles that includes the mud turtles and musk turtles. The family contains 25 species within four genera, but taxonomic reclassification is an ongoing process, so many sources vary on the exact num ...

including six species commonly known as musk turtles. The genus is endemic to

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, occurring in the eastern third of the US and southeast Ontario, Canada. Musk glands positioned near the bridge of the shell can produce foul smelling secretions when the turtles are threatened, although gentle handling does not normally provoke a response. ''Sternotherus'' are moderately small turtles, with the largest species in the genus, the razor-backed musk turtle ('' S. carinatus''), attaining a maximum of 17.6 cm. in shell length. The

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

is characteristically oval and domed (an exception being the flattened musk turtle, '' S. depressus''), with most species having one or three keels on the back which may become smoother and obscure with age in some species. Musk turtles are generally drab in color, mostly black, gray, brown, olive, or ocher, which aid in camouflaging them in their natural habitats. The head is relatively large and stout, marked with spots, streaks, or strips. The

plastron The turtle shell is a shield for the ventral and dorsal parts of turtles (the Order (biology), order Testudines), completely enclosing all the turtle's vital organs and in some cases even the head. It is constructed of modified bony elements such ...

has only 10 or 11 scutes, as opposed to 12, a more common condition in North American turtles. The tail is short, with males having a horny claw like tip. ''Sternotherus'' are largely aquatic, however some species frequently bask on fallen logs or rocks emerging from the water, and eastern musk turtles ('' S. odoratus'') occasionally leave the water to forage. ''Sternotherus'' are

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

and opportunistic generalist in their diet, although inclining toward being carnivorous, with

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

(

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

and

bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

) and insects making up a significant percentage of their diet. Some older adults develop large musculature on the head and expanded, crushing jaw surfaces aiding in the consumption of mollusk. Musk turtles are

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

with females producing one to six clutches a year. The typical clutch size is two to four eggs, although clutches may range from one to 13. The sex of the hatchlings is determined by the incubation temperature. The eggs are deposited in shallow nest excavated on the banks or in woodlands a few meters from the water. Eggs may be laid singly, or in groups, and some species are known to share communal nesting areas.Ernst, Carl, H. and Jeffrey E. Lovich. 2009. ''Turtles of the United States and Canada, 2nd. Ed.'' The Johns Hopkins University Press. Baltimore, MD. xii, 827 pp.

Etymology

The generic name ''Sternotherus'' is Greek meaning hinged breast or chest, referring to the hinged

.Zug, George. 1986.
Sternotherus.
' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles. 397:1-3. The trivial names, or specific epithets include: ''carinatus'' – Latin for keeled in reference to the shape of the

;Iverson, John B. 1979.
Sternotherus carinatus
'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles. 226:1-2. ''depressus'' – Latin for pressed down or low also referring to the shape of the carapace;Iverson, John B. 1977.
Sternotherus depressus
'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles. 194: 1-2. ''intermedius'' – Latin for intermediate, historically believed to be a hybrid from between ''S. minor'' and ''S. peltifer'';Scott, Peter A., Travis C. Glenn, and, Leslie J. Rissler. 2017. ''Resolving taxonomic turbulence and uncovering cryptic diversity in the musk turtles (Sternotherus) using robust demographic modeling.'' Molecular Phylogenetics and Evolution. 120: 1-15. ''minor'' – Latin referencing its relatively small size compared to ''S. carinatus'';Iverson, John B. 1977.
Sternotherus minor.
' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles. 195: 1-2. ''odoratus'' – Latin for having an odor, referring the smell of the musk produced by its scent glands;Reynolds, Samuel L. and Michael E. Seidel. 1982.
Sternotherus odoratus.
' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles. 287: 1-4. ''peltifer'' – Latin meaning bearing a small shield, in reference to the small size of the scutes on the bridge the species.

Taxonomy

''Sternotherus'' is one of four genera in the family

including: narrow-bridged musk turtles (''

Claudius Tiberius Claudius Caesar Augustus Germanicus ( ; ; 1 August 10 BC – 13 October AD 54), or Claudius, was a Roman emperor, ruling from AD 41 to 54. A member of the Julio-Claudian dynasty, Claudius was born to Nero Claudius Drusus, Drusus and Ant ...

''), American mud turtles (''

Kinosternon ''Kinosternon'' is a genus of small aquatic turtles from the Americas known commonly as mud turtles. Geographic range They are found in the United States, Mexico, Central America, and South America. The greatest species richness is in Mexico, a ...

''), giant musk turtles ('' Staurotypus''), and musk turtles (''Sternotherus''). ''Sternotherus'' are closely related, similar in appearance, and sympatric in much of their range with some species of mud turtles (''Kinosternon''), and the two genera constitute the subfamily Kinosterninae within the family Kinosternidae. In the past some taxonomist placed ''Sternotherus'' in the synonymy of the genus ''Kinosternon''Iverson, John B., 1991. ''Phylogenetic hypotheses for the evolution of modern kinosternine turtles.'' Herpetological Monographs, No. 5: 1-27.Iverson, John B. 1992. ''A Revised Checklist with Distribution Maps of the Turtles of the World.'' Green Nature Books Homestead, Florida. 363 pp. but they are generally regarded as two separate genera with six species currently (2022) recognized in the genus ''Sternotherus''.Uetz, Peter, Paul Freed, Aguilar, R. & Hošek, J. (eds.) (2021) ''The Reptile Database'': http://www.reptile-database.org, (accessed March 5, 2022) Fossil species *''† Sternotherus palaeodorus'' ''

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

Description

Turtles in the genus ''Sternotherus'' are very similar to the American

mud turtle ''Kinosternon'' is a genus of small aquatic turtles from the Americas known commonly as mud turtles. Geographic range They are found in the United States, Mexico, Central America, and South America. The greatest species richness is in Mexico, ...

s in the genus ''

'', but tend to have a more

dome A dome () is an architectural element similar to the hollow upper half of a sphere. There is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a m ...

, with a distinctive keel down the center of it. '' Sternotherus odoratus'' typically grows to only in straight carapace length at full maturity, with females often being larger than males.

Distribution

The genus ''Sternotherus'' is endemic to North America. It occurs in the approximant eastern third of the US and extreme southeast

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 ...

, Canada. The eastern musk turtle (''S. odoratus''), the most wide-ranging species of the genus, occurs in southern

Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...

, south to

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 ...

, west into eastern

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

, and

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

, and north to southeast

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

, southern

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

, and the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

region of southern Ontario. It is generally absent from higher elevations in the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

. The other species in the genus largely occur within the southern regions of the eastern musk turtle's range. Two species have relatively limited distributions, the flattened musk turtle (''S. depressus'') is endemic to north-central

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 ...

in the

Black Warrior River The Black Warrior River is a waterway in west-central Alabama in the southeastern United States. The river rises in the extreme southern edges of the Appalachian Highlands and flows 178 miles (286 km) to the Tombigbee River, of which the ...

basin above the

fall line A fall line (or fall zone) is the area where an upland region and a coastal plain meet and is noticeable especially the place rivers cross it, with resulting rapids or waterfalls. The uplands are relatively hard crystalline basement rock, and the ...

, and the intermediate musk turtle (''S. intermedius'') is found in southeastern Alabama and adjacent areas of the

Florida panhandle The Florida panhandle (also known as West Florida and Northwest Florida) is the northwestern part of the U.S. state of Florida. It is a Salient (geography), salient roughly long, bordered by Alabama on the west and north, Georgia (U.S. state ...

in the Choctawhatchee, Conecuh,

Yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

Pea Pea (''pisum'' in Latin) is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name ''Pisum sativum' ...

, Blackwater, and Escambia rivers. The razor-backed musk turtle (''S. carinatus'') occurs throughout

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

, and neighboring areas of

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

, Oklahoma, and Texas. The loggerhead musk turtle (''S. minor)'' is found in extreme southeast Alabama,

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 ...

, and northern Florida. The stripe-necked musk turtle (''S. peltifer'') predominantly occurs in Alabama and Mississippi with some peripheral records from Georgia, and Louisiana, and ranging into northern watersheds in eastern

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

with marginal records from

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

, and

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

.Powell, Robert, Roger Conant, and Joseph T. Collins 2016. ''Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition.'' Boston and New York: Houghton Mifflin Harcourt. xiii + 494 pp. ages 227-229

Diet

''Sternotherus'' are omnivorous. The loggerhead (''S. minor'') and stripe-necked musk turtle (''S. peltifer'') have been described as opportunistic generalist tending toward carnivory.

Mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

make up a significant portion of the diet in all species, particularly adults. Juveniles and sub-adults (under 5 cm.) feed on a higher percentage of aquatic insects, algae, and carrion. An

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

change in diet occurs and adults shift to an omnivorous diet with a high percentage of mollusk. Food items include mollusks (

and

), insects (including larva, adults, aquatic and terrestrial),

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s (crayfish and crabs), worms (earthworms and leeches), amphibians (tadpoles and small frogs),

carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...

, filamantous green algae, parts of vascular plants and seeds (e.g. ''

Prunus ''Prunus'' is a genus of flowering plant, flowering trees and shrubs from the family (biology), family Rosaceae. The genus includes plums, cherries, peaches, nectarines, apricots and almonds (collectively Drupe, stonefruit). The genus has a cosm ...

'', ''

Sambucus ''Sambucus'' is a genus of between 20 and 30 species of flowering plants in the family Adoxaceae. The various species are commonly referred to as elder, with the flowers as elderflower, and the fruit as elderberry. Description Elders are mostl ...

'', ''

Ulmus Elms are deciduous and semi-deciduous trees comprising the genus ''Ulmus'' in the family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical- montane regions of North America and Eurasia, ...

'', '' Podostemum''). Some novel and less common documented food items include spiders, millipedes, small fish and fish eggs,

isopods Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

, and small turtles. The flattened musk turtle (''S. depressus'') is known to feed on introduced Asian clams (''Corbicula maniliensis'').Marion, Ken R., William A. Cox, and Carl H. Ernst. 1991. ''Prey of the flattened musk turtle, Sternotherus depressus.'' Journal of Herpetology 25.3 (1991): 385-387Mahmoud, I. Y. 1968. ''Feeding behavior in kinosternid turtles.'' Herpetologica, 24(4), 300-305. The razor-backed (''S. carinatus'') and eastern musk turtles (''S. odoratus'') are known to be bottom feeders, often searching with the neck extended and probing the mud and sand with their heads.

Olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

is probably important in the location and selection of food items. However, musk turtles occasionally feed at the surface and are also known to eat out of the water. Eastern musk turtles (''S. odoratus'') have occasionally been observed leaving the water at dusk to feed on slugs on land. Some larger adults develop hypertrophied head musculature and expanded crushing surfaces on both the upper and lower jaws that aid in eating mollusk. One study concluded razor-backed (''S. carinatus'') and eastern musk turtles (''S. odoratus'') were "euryphagous with food preferences directly related to the availability of food." Another study found the diet of the eastern musk turtle (''S. odoratus'') varied seasonally and males ate more insects and females more snails.Bancroft, G. Thomas, J. Steve Godley, Dena T. Gross, N. Nan Rojas, Dareth A. Sutphen, and Roy W. McDiarmid. 1983. ''Large-scale operations management test of use of the white amur for control of problem aquatic plants: the herpetofauna of Lake Conway: species accounts''. Misc, Pap. A-85-5. Army Eng. Waterw. Exp. Stn. Vickburg, Mississippi. Digestive turnover rates, from ingestion to defecation, of 49 hours (''S. odoratus'') to 57 hours (''S. minor, S. peltifer'') have been reported, although temperatures may influence these times.Parmenter, Robert R. 1981. ''Digestive turnover rates in freshwater turtles: the influence of temperature and body size.'' Comparative Biochemistry and Physiology Part A: Physiology 70.2: 235-238.

Habitat

''Sternotherus'' are largely aquatic, but some species bask frequently, and may occasionally leave the water to forage and lay eggs. Fallen logs and deadwood submerged and emerging from the water are important for shelter and basking sites for all species of ''Sternotherus''. Habitat preferences varies among some species. The eastern musk turtle (''S. odoratus'') tends to be generalist and may occur in almost any body of water, as are loggerheads (''S. minor'') to a lesser extent, although water with slow or no currents, soft bottoms, and shelter in the form of logs and rocks are usually preferred over very deep water and swift currents. Eastern musk turtles have been found at depths of 9 meters but, shallower water (ca. 1 meter), are more typical. Brackish water is usually avoided. Depths of 0.5–1.5 meters are typical for loggerheads (''S. minor''), but they have been found at 13 meters.Hensley, F. R. 1995. ''Sternotherus minor (loggerhead musk turtle) Foraging depth.'' Herpetological Review 26: 99. The razor-backed musk turtle (''S. carinatus'') favors the relatively deeper waters of rivers, creeks, bayous, and associated oxbow lakes, backwater swamps, and floodplains where slower currents and soft substrates are found. The stripe-necked musk turtle (''S. peltifer'') are lotic, preferring the currents of rivers and streams although they can be abundant in lakes and impoundments along these waterways as well. The flattened musk turtle (''S. depressus'') is an inhabitant of clear, rocky to sandy bottom creeks and streams above the fall line, typically 1.5 meters or less in depth, taking shelter under logs and rocks, or burrowing in the sand. The intermediate musk turtle (''S. intermedius'') was regarded as a hybrid between ''S m. minor'' and ''S. m. peltifer'' as recently as 2017, and few if any studies specifically examining the ecology of the species have been published (as of 2022). In one ecological study of kinosternid turtles conducted over five years in

, permanent bodies of lotic (moving) water in wooded areas such as large rivers and creeks were the favored habitats of both razor-backed (''S. carinatus'') and eastern musk turtles (''S. odoratus''), however, ''S. carinatus'' was generally found in deeper water. No sexual, age, or seasonal differences were observed in habitat selection other than juveniles preferred shallower water than adults. The two species were strictly aquatic and terrestrial migrations occurred only during the breeding season. When inactive, both specie hid under rocks, logs, and overhanging banks, but did not show the burrowing proclivities that ''

'' did. Turtles were found in abundance in quiet waters where submerged and floating vegetation such as algae, '' Nasturtium'', ''

Polygonum ''Polygonum'' is a genus of about 130 species of flowering plants in the buckwheat and knotweed family Polygonaceae. Common names include knotweed and knotgrass (though the common names may refer more broadly to plants from Polygonaceae). In the ...

'', '' Myriophyllum'', '' Najas'', and ''

Potamogeton ''Potamogeton'' is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed (''Elodea canadensis' ...

'' formed in mats and provided food and suitable shelter. Light intensity, pH levels, and transparency of water were examined, although it was concluded they were probably not directly limiting factors for the turtles, but did affect the distribution of vegetation and prey which provided food for the turtles.Mahmound, I. Y. 1969. ''Comparative ecology of the kinosternid turtles of Oklahoma.'' Southwestern Naturalist 14: 31-66.

Behavior

''Sternotherus'' is a highly aquatic genus. But some species, like the common musk turtle, are known to bask on fallen trees and coarse woody debris on shorelines. The thermal activity range and annual activity period was longer for ''Sternothaerus'' than ''Kinosternon''

Gallery

File:Razorback Musk Turtle (Sternotherus carinatus) (24797975727).jpg, Razorback musk turtle (''Sternotherus carinatus''), Saline County, Arkansas (July 28, 2017) File:Razorback Musk Turtle (Sternotherus carinatus) Hardin Co. Texas. photo W. L. Farr.jpg, Razorback musk turtle (''Sternotherus carinatus''), in-situ, Hardin County, Texas (October 10, 2013) File:Sternotherus odoratus, Kerr Co. TX; 8 May 2014.jpg, Eastern musk turtle (''Sternotherus odoratus''), in-situ, Kerr County, Texas (8 May 2014)

References

External links

*Walker, Matt (2010).
Turtle 'super tongue' lets reptile survive underwater".
''BBC Earth News''. 20 May 2010. * {{Authority control Taxa named by Thomas Bell (zoologist) Turtle genera