Overlooked and forgotten: A discovery of serial thoracopodal epipods in two species of Boreomysis, with a review of similar findings across the Mysidae (Mysidacea, Malacostraca)

This study investigates the presence and interpretation of thoracopodal epipods in mysidaceans, especially in Mysida. Traditionally, Mysida have been described as lacking thoracopodal epipods, with the notable exception of the first thoracopod. This absence of serial thoracopodal epipods starkly contrasts with the branched epipodal gills observed in Lophogastrida and most non-peracaridan Malacostraca. Despite the broadly stated absence of thoracopodal epipods in Mysida, a few mentions in mysid literature suggest the potential existence of epipodal processes in certain species. In this paper, we present two new instances of serial epipodal vestigia found on the thoracopods of Boreomysis spp., alongside a review of various observations of putative thoracopodal epipods and gills reported in the existing mysid literature.