Unexpected diversity: a new species of the boreal gastropod genus Bogasonia (Cephalaspidea: Cylichnidae) from the subantarctic and its implications for biogeography of Toledoniinae

Abstract

The genus Bogasonia comprises three little known microgastropods species from cold boreal waters with a unique periostracum that forms two spiral cords not bounded to the shell surface. Bogasonia maradoniana n. sp. is described after adults, juveniles and spawn from a large population collected at 50°30′40′′S, 68°02′33′′W, 62 m, of Santa Cruz Province, Argentina. The new species is the frst described from the Southern Hemisphere and points out a remarkable case of disjunct distribution at the genus level towards cold waters of both hemispheres. The states of knowledge of Bogasonia and Toledonia species are commented and key information coming from fossil record is provided for a better taxonomic and biogeographic understanding of Toledoniinae. A direct-life cycle is reported for the new species and is expected for all species of both genera. At least two independent migration events should have occurred during the last 20 million of years to explain the current distribution of Toledoniinae.