The East Asian common octopus has long been synonymized with the Atlantic and Mediterranean species Octopus vulgaris Cuvier, 1797. However, evidence from molecular genetic studies has firmly established that the so-called cosmopolitan common octopus is in fact a group of several biogeographically distinct populations which form a complex of species with closely similar morphology. Here, a diagnosis and brief description are provided which distinguish the East Asian common octopus from O. vulgaris, and as a suitable name for it a former junior synonym of O. vulgaris is identified as a valid species: Octopus sinensis d'Orbigny, 1841. A neotype is designated. Voucher material includes specimens collected in Japan by Philipp Franz von Siebold and deposited in the National Museum of Natural History - Naturalis - in Leiden; and others that were studied by Madoka Sasaki in preparation for the detailed description of this species (as O. vulgaris) in a monograph on Japanese Cephalopoda published in 1929. At present, all species in this complex (particularly O. vulgaris and the East Asian species here identified as O. sinensis) are highly vulnerable to overfishing, so recognizing O. sinensis as a species distinct from O. vulgaris is an important step towards improving sustainable fisheries management policies for each species in this group of commercially valuable octopuses.
2016 The Japanese Society of Systematic Zoology