Trionychidae

The Trionychidae are a taxonomic family of a number of turtle genera commonly known as softshells. They are also sometimes called pancake turtles (although they are distinct from the pancake tortoise). Softshells include some of the world's largest freshwater turtles, though many can adapt to living in highly brackish areas. Members of this family occur in Africa, Asia, and North America. North American members of genus Trionyx were fairly recently (1987) assigned the resurrected genus name Apalone by Meylan, though they are still listed semicorrectly as Trionyx in some texts.

Characteristics

They are called "softshell" because their carapaces lack horny scutes (scales), though the spiny softshell, Apalone spinifera, does have some scale-like projections, hence its name. The carapace is leathery and pliable, particularly at the sides. The central part of the carapace has a layer of solid bone beneath it, as in other turtles, but this is absent at the outer edges. Some species also have dermal bones in the plastron, but these are not attached to the bones of the shell. The light and flexible shell of these turtles allows them to move more easily in open water, or in muddy lake bottoms. Having a soft shell also allows them to move much faster on land than most turtles. Their feet are webbed and are three-clawed, hence the family name "Trionychidae," which means "three-clawed." The carapace color of each type of softshell turtle tends to match the sand and/or mud color of its geographical region, assisting in their "lie and wait" feeding methodology.

Spiny softshell turtle

The spiny softshell turtle (Apalone spinifera) is a species of softshell turtle, one of the largest freshwater turtle species in North America. They get their name from the spiny, cone-like projections on the leading edge of their carapaces, which are not scutes (scales).

Geographic range

The spiny softshell has a wide range, extending throughout much of the United States, as well as north into the Canadian provinces of Ontario and Quebec, and south into the Mexican states of Tamaulipas, Nuevo León, Coahuila and Chihuahua.

Taxonomy

The species was first described by Charles Alexandre Lesueur in 1827. It has been redescribed numerous times, leading to some confusion in its taxonomy. The recognized subspecies differ in the markings on the carapace, on the sides of the head, and on the feet. However, these 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.