Cephalopod

Cephalopods were a type of animal which included octopi, squids, cuttlefish and the like.

Throughout the universe, various cephalopod species existed. This was one of the many shapes that recurred throughout the universe, along with insectoid and humanoid. The Nestenes were a sentient, hive minded race who, in their natural form, were cephalopods.

Ianto Jones told his boyfriend Jack Harkness that he had a fear of a lover leaving him equally for "men, women, or cephalopods." (TWN: The House that Jack Built)