The chondrichthyan fauna from the Middle-Late Triassic of Guanling (Guizhou province,SW China)

The Recent volutids Cymbiola and Melo burrow in a forward direction. This agrees well with the spiral terrace pattern observed in Eocene Volutidae, thus strengthening the idea that they were forward burrowers as well. The presence of collabral terraces near the aperture in the Cassidae suggests an oblique burrowing direction, by convergence with the Nassariidae. This is confirmed by observations on living cassids. The sutural canals and associated structures of the Olividae and Seraphidae are functional in detecting whether the posterior region of the shell is buried. This confirms the idea that fossil Strombidae possessing similar features were burrowers.

In contrast with these “predictable”; observations, burrowing was observed in a few gastropods the shell morphology of which would seem to exclude such behaviour, such as Architectonica, Cymatium, Volema and Bolinus. Thus, a few morphologic criteria appear to be reliable and of general applicability in inferring burrowing habits in gastropods. At the same time, the broad variety of burrowing mechanisms and life habits of gastropods makes it unlikely that general criteria will ever be found to exclude burrowing habits on the basis of shell morphology.