[2] Most Apalone species are restricted to the United States, though the range of the spiny softshell, A. spinifera, extends into southern Canada and northern Mexico.

[2] Apalone is a fairly new classification, resurrected by Meylan in 1987,[3] assigned to North American species of the genus Trionyx.

Molecular phylogenetic studies generally suggest that Apalone is most closely related to the highly endangered Asian genus Rafetus, with the two genera most likely diverging during the Late Eocene.

The ancestral Apalone most likely crossed from Asia into North America via Beringia, taking advantage of the warm climate during the Eocene.

These two species are much older than any other remains assigned to Apalone, and even predate the presumed divergence of the genus based on molecular phylogenies.