Apalone is a fairly new classification, resurrected by Meylan in 1987, assigned to North American species of the genusTrionyx, though they are still listed as Trionyx in some texts. (Trionyx now refers specifically to certain softshell species found mainly in Africa.)
Turtles of the genusApalone exhibit marked sexual dimorphism. 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.