On the geographical and stratigraphical distribution of the nestling bivalve Petricola ramirezi Araya & Osorio, 2019 (Bivalvia: Veneridae)

Petricola ramirezi Araya & Osorio, 2019, a shallow-water nestling petricolid bivalve, was originally described from specimens collected washed ashore at El Tabo, central Chile (33°27′S, 071°38′W). This species is unique from all other bivalve species in the area in nestling inside empty shells of the barnacle Balanus laevis. In this study, we present new geographic records for this species based on specimens collected at several localities in northern and central Chile. These results extend the geographical distribution of P. ramirezi by approximately 1,089 km from its only previously known locality at El Tabo northwards to Caldera (27°04′S, 070°49′W) and southwards to Lirquén (36°42′S, 072°58′W). Additionally, we present the first fossil record for P. ramirezi based on specimens collected nestling inside empty shells of B. laevis from a Pleistocene site in the El Morro area, Caldera, northern Chile. These results confirm the presence of this species along an expanded geographical distribution on the present-day Chilean coasts and reveal that P. ramirezi has been present in the northern part of the country since at least the Pleistocene. The particular and specialized lifestyle of this species, nestling inside empty barnacle shells, suggests that this strategy—providing protection from predators and from sudden environmental changes—may have contributed to the survival of this species in the area since the Pleistocene.