Trionychidae

Trionychidae is a family of turtles, commonly known as softshell turtles or simply softshells. The family was described by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to living in highly brackish waters. Members of this family occur in Africa, Asia, and North America, with extinct species known from Australia. Most species have traditionally been included in the genus Trionyx, but the vast majority have since been moved to other genera. Among these are the North American Apalone softshells that were placed in Trionyx until

Axestemys is an extinct genus of softshell turtle that lived from the Late Cretaceous to the Eocene in western North America and Europe.

Plastomenus is an extinct genus of turtle that inhabited western North America during the early Paleogene period.