B is an undescribed species of bigfin squid known only from a single immature specimen collected in the northern Atlantic Ocean.

It is characterised by its dark epidermal pigmentation, which is epithelial, as opposed to the chromatophoral pigmentation found in other Magnapinna species.

The only known specimen of Magnapinna sp.

B is a juvenile male of 95-millimetre (3.7 in) mantle length (ML) held in the Bergen Museum.

SARS (MAR-ECO cruise super station 46, local station 374) on July 11, 2004, at 42°48′N 29°18′W / 42.8°N 29.3°W / 42.8; -29.3.