Evolution and systematics
The household is most carefully associated to the Dermatemydidae. Two monophyletic subfamilies are acknowledged: the Kinosterninae (together with the dwelling genera Kinosternon and Sternotherus) and the Staurotypinae (together with the dwelling genera Staurotypus and Claudius). Fossils of every subfamily are recognized from as early because the Eocene.
These turtles are typically small (normally lower than Eight in [20 cm]) with rectangular, reasonably domed shells. The Mexican big musk turtle (Staurotypus triporcatus) is the most important species, reaching a shell size of 15 in (38 cm). The plastron has one (Staurotypus, Sternotherus,some Kinosternon), two (most Kinosternon), or no hinges (Claudius), and is usually decreased (with 11 or fewer epidermal scutes), though some Kinosternon have a plastron in depth sufficient to shut the shell opening fully. The kinosternine plastron lacks the entoplastral bone present in staurotypines. All members produce a pungent musk from glands placed in entrance of and behind the bridge space between the plastron and the carapace. The head of some species could also be enormously enlarged (a bonus for mollusk feeding), and all have sensory barbels on the chin.
Eastern and southern North America to Argentina, from sea stage to 8,500 ft (2,600 m).
Within their ranges, these turtles might be present in practically any freshwater aquatic system. Because of their comparatively poor swimming capacity, they like slow-moving or nonetheless waters (e.g., everlasting ponds with lush vegetation or backwaters of lotic techniques). However, some species inhabit extremely seasonal ephemeral ponds which can solely include water for a couple of months of every year.
In seasonal environments (excessive latitude or deserts), these turtles have brief annual exercise intervals (three months or much less in some instances) and spend the remainder of the year hibernating or estivating underground. In wetter, extra tropical habitats, they're energetic year-round. Most are extremely aquatic, not often leaving the water besides to nest, though a couple of species could spend appreciable time foraging terrestrially (particularly through the moist seasons). Some species are energetic primarily through the day, others primarily at night time, and nonetheless others could also be discovered energetic at any time.
Feeding ecology and food plan
These turtles are all primarily carnivorous, feeding primarily on mollusks (snails and clams), crustaceans, bugs, annelids, and even fish (normally as recent carrion). Some are extremely specialised mollusk feeders and eat little else. However, some species, particularly these with in depth terrestrial habits and these in extremely seasonal ponds, embrace plant materials (primarily seeds) of their diets.
In most species the males are bigger than the females, have a protracted muscular tail with an epidermal “nail” on the finish, and have tough patches of scales (clasping organs) on the again of their hind legs. As a outcome, male courtship is forceful and not very elaborate; females could choose mates primarily based on the male’s capacity to subdue or restrain her actions. All mating happens within the water. Females lay one to 12 eggs (normally three to six) in every clutch and the clutch dimension tends to be higher in bigger turtles. Many species lay a number of clutches (up to six per year). Eggs are rectangular, brittle shelled, and vary in dimension from 0.9 0.6 in (2.3 1.Four cm) within the stinkpot (Sternotherus odoratus) to 1.7 1.Zero in (4.Four 2.6 cm) within the Mexican big musk turtle. In some species the nests are poorly constructed and the eggs are merely laid amongst leaf litter; nonetheless, others dig extra typical flask-shaped nests, and nonetheless others dig a physique pit or bury themselves fully beneath the bottom earlier than digging a nest chamber. Incubation is usually fairly lengthy (e.g., 75 days to a year) and the embryos of some species exhibit diapause throughout early growth or estivation later in growth, presumably as diversifications to keep away from inhospitable instances of the year for a hatchling turtle. Staurotypus is exclusive on this household in having heteromorphic intercourse chromosomes (as in people). All others which have been studied exhibit temperature-dependent intercourse willpower, with heat temperatures producing females, intermediate temperatures producing principally males, and nonetheless cooler temperatures once more producing principally females.
Most kinosternid species are frequent, reaching wonderful inhabitants densities (as excessive as 1,200 per 2.5 acres [1 ha]). However, two tropical, one subtropical, and one temperate species are listed as Vulnerable on the IUCN Red List. The two tropical species ( Okay. dunni and Okay. angustipons) are lowland varieties with very restricted ranges and therefore are most likely affected most negatively by habitat destruction. The subtropical species (Okay. sonoriense) lives primarily in everlasting water techniques within the deserts of the U.S. Southwest; human competitors for water sources has eradicated many of the habitat for this species. The temperate species ( Sternotherus depressus) additionally has a restricted distribution within the everlasting streams of north-central Alabama; habitat destruction related to coal mining and forest clear-cutting appears to have prompted the declines on this species.
Significance to people
Most species of mud and musk turtles don't have any significance to people, besides as aquarium pets. A number of tropical species could also be eaten regionally by indigenous people, however not at ranges excessive sufficient to get rid of populations.