Abstract

Eight species of Architectonicidae have been reported for lower Miocene deposits in continental Chile. One of these species is Architectonica karsteni, which had an inferred geographic range, for this epoch, extending from Costa Rica to central Chile (~8° N to 34° S), and even in the Caribbean. There is no evidence of the current presence of the family immediately off the coast of Chile. We report the discovery of living specimens and shells of A. karsteni at four seamounts at ~200 m water depth in the recently created Nazca–Desventuradas Marine Park, located ~900 km west of Chile. Morphological identification was based on protoconch diameter, coloration patterns, and teleoconch sculpture. We also provide sequence data for portions of the mitochondrial COI and 16S rRNA genes as a contribution toward future population-level and phylogenetic analyses of this poorly known group. Insight on the habitat of the species based on underwater imagery is also provided. This new record extends the geographic distribution of A. karsteni ~20° southward from its current recorded range (i.e., Baja California to Peru). The finding of this species contributes to the knowledge of the fauna of these seamounts, and ultimately informs and boosts conservation efforts of these relatively pristine habitats.