The neogastropod molluscan family Pseudolividae is one of several clad
es that have undergone a decline in diversity and a reduction in geogr
aphical distribution during the Cenozoic. After originating in the Lat
e Cretaceous (Campanian), the group peaked in number of species during
the Paleocene. A drop in diversity after the early Eocene was followe
d by successive contractions in geographical range at the end of the E
ocene, during and at the end of the Miocene, and at the end of the Pli
ocene. Like several other gastropod groups with a similar history, the
Pseudolividae are almost absent from the rich Indo-West Pacific biota
, with only two out of the sixteen living members of the family being
known from the margins of the Indo-West Pacific region today. Relict g
roups with a significant Neogene record in Europe, by contrast, typica
lly occur in the living biota mainly or exclusively in the central Ind
o-West Pacific. The decline and geographical contraction of the Pseudo
lividae occurred despite the post-Eocene evolution of two morphologica
l innovations, the parietal tooth or rib at the adapical end of the in
ner lip, and lirae (spiral ribs) on the adaxial (inner) side of the ou
ter lip.