Bigfin Reef Squid.

The bigfin squids are a group of rarely seen cephalopods with a very distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae. The family is known only from larval, paralarval, and juvenile specimens, but some authorities believe the adult creature has been seen: Several videos have been taken of animals nicknamed the "long-arm squid", which appear to have a similar morphology. Since none of the adult specimens have ever been captured or sampled, it remains uncertain if they are the same genus, or only distant relatives.

Physical specimens

The first record of this family comes from a specimen (Magnapinna talismani) caught off the Azores in 1907. However, due to the damaged nature of the find, very little information could be discerned and it was lumped in with the mastigoteuthids, first as Chiroteuthopsis talisman and later as Mastigoteuthis talismani. In 1956 a similar squid (Magnapinna sp. C) was caught in the South Atlantic, but little was thought of it at the time. The specimen was illustrated in Alister Hardy's The Open Sea (1956), where it was identified as Octopodoteuthopsis.

During the 1990s two more immature specimens were found in the Atlantic (Magnapinna sp. A), and three more were found in the Pacific (Magnapinna pacifica). Researchers Michael Vecchione and Richard Young were the chief investigators of the finds, and eventually linked them up to the two previous specimens, erecting the family Magnapinnidae in 1998, with Magnapinna pacifica as the type species. Of particular interest was the very large fin size, up to 90% of the mantle length, that was responsible for the animals' nickname. The Magnapinna pacifica finds have been called a "cryptid" by cryptozoologist Karl Shuker, who was aware of the other specimens and video evidence but deems it a cryptid because its adult form currently remains undetermined by science.

A single specimen of a fifth species, Magnapinna sp. B, was collected in 2004. Magnapinna sp. A was described as Magnapinna atlantica in 2006.

Feeding behavior

Very little is known about the feeding behavior of these squid. Scientists have speculated that bigfin squid feed by dragging their tentacles along the seafloor, and grabbing edible organisms off the floor. Alternatively, they may simply use a trapping technique, waiting passively for prey to bump into their arms. If so, they would be the only known passive predators among cephalopods.