Evidence for convergent evolution of brooding in a unique gastropod from Lake Tanganyika: anatomy and affinity ofTanganyicia rufofilosa(Caenogastropoda, Cerithioidea, Paludomidae)

Tanganyicia rufofilosais an enigmatic gastropod endemic to Lake Tanganyika and unique among lake species in possessing a brood pouch within the head‐foot. However, the only existing anatomic studies of the species are incomplete. Hence, the affinity of this species to other Tanganyikan gastropods and the evolution of viviparity among limnic Cerithioidea are unclear. The anatomic redescription and reinterpretation of reproductive homologies presented here revealed several features from the midgut and kidney that are informative concerning the phylogeny of Lake Tanganyika gastropods. In addition, the complex reproductive anatomy of both sexes is described. A rare accessory gland is present in males that is hypothesized to function in spermatophore formation and to be homologous to the ‘penis’ of some cerithioideans, an otherwise predominantly aphallic group. The structurally unique brood pouch, restricted to the mesopodial portion of the foot, is described and demonstrated to be unknown among viviparous cerithioideans. In contrast to the view that the cerithioideans of Lake Tanganyika represent an endemic radiation of Thiaridae, based on these new dataT. rufofilosaappears to be allied to the Paludomidae.