Decline and contraction: The history of the relictual Gastropod family Pseudolividae

Abstract

The neogastropod molluscan family Pseudolividae is one of several clades that have undergone a declinein diversity and a reduction in geographical distribution during the Cenozoic. After originating in the Late Cretaceous (Campanian), the group peaked in number of species during the Paleocene. A drop in diversity after the early Eocene was followed by successive contractions in geographical range at the end of the Eocene, during and at the end of the Miocene, and at the end of the Pliocene. Like several other gastropod groups with a similar history, the Pseudolividae are almost absent from the rich Indo-West Pacific region today. Relict groups with a significant Neogene record in Europe, by contrast, typically occur in the living biota mainly or exclusively in the central Indo-West Pacific. The decline and geographical contraction of the Pseudolividae occurred despite the post-Eocene evolution of two morphological innovations, the parietal tooth or rib at the adapical end of the inner lip, and lirae (spiral ribs) on the adaxial (inner) side of the outer lip.