Fig. 9

Illustration of male-to-female “sex-reversals” in the Perisphinctoidea: A the Kimmeridgian dimorphic Perisphinctidae Pectinatites (Virgatophinctoides) reisiformis Cope. All specimens are from Cope [30], and (B) the Kimmeridgian Aspidoceratidae dimorphic pair Physodoceras [M]—Sutneria [m]. All specimens are from [49]. In (A), the “forma hermaphrodita” individual appears intermediate in size between the [m] and [M], has the sculpture typical of the [M], but sporadically develops structures resembling those of the horn of the [m]. In (B), the “forma hermaphrodita” individual starts with a bituberculate sculpture typical for female and develops the ornamentation and lappet typical of the [m] on the outer whorl. Specimens are figured using the original scale