carapace): | | | | | | | | | conical, equilateral | | X | X | X | X | | | | | | | | | | | | | reduced or absent | X | | | | | X | X | X | X -------------------------------------+---+---+---+---+---+---+---+---+--- Head (PL/HW, fig. 3): | | | | | | | | | wide | X | | | X | | X | X | X | | | | | | | | | | narrow | | X | X | | X | | | | X -------------------------------------+---+---+---+---+---+---+---+---+--- Carapace (CL/CW, fig. 4): | | | | | | | | | wide | | X | X | X | X | X | | | X | | | | | | ¦ | | | narrow | X | | | | | X | X | X | -------------------------------------+---+---+---+---+---+---+---+---+--- Level of Carapace Width (CL/PCW, | | | | | | | | | fig. 5): | | | | | | | | | middle of carapace | X | X | X | X | | | | | X | | | | | | | | | farther posteriorly | | | | | X | X | X | X | -------------------------------------+---+---+---+---+---+---+---+---+--- Snout (HW/SL, fig. 6): | | | | | | | | | long | | X---X | X | X---X | | | X | | | | | ¦ ¦ | | | short | X | | | | X---X | X | X | -------------------------------------+---+---+---+---+---+---+---+---+--- Fossils The known occurrence of fossil trionychids throughout the world indicates a former distribution more widespread than the family has today; the principal difference in the former and present distributions is the lack of living softshells in Europe.