Remipedia is a class of blind crustaceans found in coastal aquifers which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in Australia, the Caribbean Sea, the Atlantic Ocean. The first described remipede was the fossil Tesnusocaris goldichi (Lower Pennsylvanian), but, since 1979, twenty-four living species have been identified with global distribution throughout the neo-tropical zone.[1,2]
Remipedes are 10–40 millimetres (0.4–1.6 in) long and comprise a head and an elongate trunk of up to forty-two similar body segments.[3 and references therein] The swimming appendages are lateral on each segment, and the animals swim on their backs. They are generally slow-moving. They have fangs connected to secretory glands; it is still unknown whether these glands secrete digestive juices or poisonous venom, or whether remipedes feed primarily on detritus or on living organisms. They have a generally primitive body plan in crustacean terms, and have been thought to be a basal, ancestral crustacean group. However, Fanenbruck et al. showed that at least one species, Godzilliognomus frondosus, has a highly organised and well-differentiated brain, with a particularly large olfactory area which is a common feature for species that live in dark environments. The size and complexity of the brain suggested to Fanenbruck et al. that Remipedia might be the sister taxon to Malacostraca, regarded as the most advanced of the crustaceans. This is also one of the reasons why it is included in the Pancrustacea hypothesis, a hypothethical clade of probably the most advanced Mandibulata. They have also been grouped together with the Cephalocarida in the Xenocarida, and recently with the hexapoda .