The role of the environment in the Nautilacea.

Abstract

The classification of the superfamily Nautilacea, which includes all post-Triassic nautiloids, rests at present on purely typological criteria. The families and genera are based on the presence of well-defined morphological characteristics. Recent studies, however, have shown that many of these characteristics are related to the mode of life of the animal, and are consequently susceptible to repeated occurrences in different lineages. The development of the ornamentation, the form of the suture line and the position of the siphuncle all appear to be closely linked to water depth and its degree of agitation. Consequently only the knowledge of the evolutionary lineages can lead to a satisfactory classification of this group.-Authors