A brain atlas of Godzilliognomus frondosus Yager, 1989 (Remipedia, Godzilliidae) and comparison with the brain of Speleonectes tulumensis Yager, 1987 (Remipedia, Speleonectidae): implications for arthropod relationships

Remipedia are rare and ancient mandibulate arthropods inhabiting almost inaccessible submerged anchialine cave systems. Their phylogenetic position is still enigmatic and subject of controversial debates. In order to contribute to this discussion we have analysed the brain of Godzilliognomus frondosusYager, 1989 from anchialine caves in the Bahamas. Bulletin of Marine Sciences 44, 1195-1206 (Remipedia, Godzilliidae) and worked out a detailed atlas and a 3D reconstruction of its brain anatomy. We compare these data to the brain of a second remipede species, Speleonectes tulumensis Yager, 1987 (Speleonectidae). Surprisingly, in comparison to the brain of other non-malacostracan crustaceans such as representatives of the Branchiopoda and Maxillopoda the remipede brain is more highly organised and differentiated. It is matched in complexity only by the brain of Malacostraca or e.g. Hexapoda. A phylogenetic analysis limited to brain anatomy across the Mandibulata strongly contradicts the prevailing hypothesis that the Remipedia are basal and ancestral crustaceans. Instead, we suggest a derived position and a placement within a Remipedia-Malacostraca-Hexapoda clade.