Subfamilia Trionychinae

Lydekker, 1889
Common softshell turtles

These softshells have the hyo- and hypoplastra separated and distinct, the xiphiplastra surrounding the lateral prong of the posteromedial process of the hypoplastra, usually four or five callosities (Rafetus has only two callosities), and lack cutaneous femoral flaps on the plastron. The nuchal bone of the carapace lacks a conspicuous ventral ridge and lies over the 1st costal bone; the posterior border of the pterygoids lacks an ascending process that touches the opisthotic. The 11 genera of this subfamily occur in Southeast Asia, New Guinea, the Middle East, Africa, and North America.