Revealing new taxa and biogeographic patterns in shallow and deep-sea Marginellidae gastropods of the Southwestern Atlantic

A comprehensive morphological analysis of Marginellidae species from shallow to deep waters off Uruguay and Argentina is presented, incorporating both traditional techniques and geometric morphometrics. Shell microstructure, radulae, protoconch, and penes are described and illustrated using SEM images. The effectiveness of geometric morphometrics in species discrimination is demonstrated. In the study area, the family includes nine living species-six of them new-distributed among four genera, including Pustinella gen. nov. These are Prunum martini, Prunum rubens, Prunum juancarlosi sp. nov., Volvarina warrenii, Volvarina castanea sp. nov., Volvarina acicularis sp. nov., Volvarina abyssalis sp. nov., Pustinella cymatilis gen. et sp. nov., and Pustinella felidamia gen. et sp. nov. These species are restricted to the Southwestern Atlantic, ranging from Rio de Janeiro, Brazil, to Burdwood Bank (∼54°S), Argentina. Five of the new species inhabit exclusively deep waters, down to 2457 m, while the remaining four occur on the continental shelf. Additionally, two poorly known antarctic species, Marginella hyalina and Marginella ealesae are compared and included in Pustinella gen. nov. Lectotype is designed for Marginella fraterculus, a synonym of P. martini, and Marginella dozei is proposed as a new synonym of V. warrenii. Geographic and bathymetric distributions of all species are detailed based on field observations and museum records. Deep-sea species show patterns of aggregation influenced by specific marine currents, whereas shelf species correspond to the Argentine and Magellanic provinces.