Debrunia occitanica nov. sp. (Monopleuridae) from the Early Aptian of SE France

Abstract

Debrunia occitanica nov. sp., described from the early Aptian platform limestones of SE France, is characterized by: a moderately convex left valve, inconspicuous radial bands and a ligament groove in a depression flanked by two longitudinal rounded edges. Debrunia occitanica nov. sp. is considered as a chronospecies belonging to a single lineage rooted in the Barremian, and including Debrunia bruni and Debrunia mutabilis. Evolutionary trends in the three species include flattening of the left valve, development of the corresponding myophores, and reduction of the radial bands. This new species has the potential to be a stratigraphic marker for the early Aptian.