A new intertidal arthrotardigrade, Prostygarctus aculeatus gen. nov., sp. nov. (Tardigrada: Heterotardigrada) from the North of Portugal (Atlantic ocean)

A new arthrotardigrade, Prostygarctus aculeatus gen. nov., sp. nov. is described from intertidal meiobenthos samples collected at Ofir beach, Esposende, North of Portugal. The new species, an armoured arthrotardigrade of the family Stygarctidae, is easily distinguished from all the other stygarctids by an unusual caudal apparatus, which consists of a very long medial spine with two lateral furca-like processes. It is also characterised by the presence of backwardly directed dorsal spines and a pair of ventral spines. Furthermore, it has four digits on each leg, ending in simple claws. The morphological peculiarities exhibited by the new species justify the establishment of a new genus and will provide useful insights to help develop our understanding of the phylogenetic relationships of armoured arthrotardigrades.