[1] The species classified under Histioteuthidae are mostly weakly muscled, moderately sized squid with a maximum mantle length of 33 cm (13 in).

They generally have very long, robust arms and a short mantle with small, rounded fins.

Their main distinguishing feature is that the eyes are different sizes and orient in different vertical directions.

This means that when the squid is positioned obliquely the eye is pointed upwards towards the surface.

It is thought that this is used to detect animals above the squid silhouetted against the sun during the day.