Terrestrial. Carapace forms rounded dome and is typically plain brown (though sometimes with a radiating pattern). Plastron plain (though sometimes with dark marks outlining scutes). Hind foot with 3 (or 4) toes. Juveniles with prominent middorsalkeel.
Aquatic. Prominent red "ear" behind eye. Reticulated, greenish carapace with back margin somewhat serrate and flaring. Underside of marginal scutes plain. Plastron with usually one dark "doughnut" per scute.
Family: Kinosternidae (Mud and Musk Turtles)
Genera: Kinosternon (American Mud Turtles) and Sternotherus (Musk Turtles)
Aquatic. Pancake-shaped with long neck and snorkel nose. Carapace mostly without pattern and smooth. Front edge of carapace without bumps. Nostrils without ridge-like projections. Feet not strongly patterned.
Aquatic. Pancake-shaped with long neck and snorkel nose. Carapace with pattern of dots and sandpaper-like texture. Front edge of carapace with bumps. Nostrils with ridge-like projections. Feet strongly patterned.
Subspecies: Pallid Spiny Softshell (A. s. pallida) and Eastern Spiny Softshell (A. s. spinifera)