This study investigates the molluscan fauna of the South Azorean Seamount Chain (SASC), which comprises several seamounts
culminating in 300–1600 m depth, separated by distances less than 200 km. Material was collected mainly by dredging and
comprises mostly empty shells. A total of over 111,000 shells representing at least 439 species (409 identified) was collected.
Larval development was inferred from protoconch morphology, and the assemblage comprises species with planktotrophic
larvae, with non-feeding planktonic larva, and with lecithotrophic larvae with direct development. The direct developers are
more prevalent among species endemic to the SASC in the upper bathyal part (300–800 m) of the seamounts, whereas most
planktotrophic species are shared with the Lusitanian seamounts and/or the European mainland. Nevertheless, there are notable
exceptions to this trend, where species with non-planktotrophic larvae are also widespread, and a large proportion of the
species with non-feeding planktonic larvae are shared with Eastern and/or Western Atlantic. Level of endemism of Mollusca
is high within the SASC (22.5% overall, 35.8% considering only the interval < 800 m) and even higher (32.6% overall) when
considering together the SASC and the Azores. The generic composition and large set of overlapping fauna suggest a strong
relation to the temperate Eastern Atlantic, whereas only 19% of the species are shared with the Western Atlantic.