Although most octopus in this family do not grow bigger than 1 foot in length, some individuals of certain species can reach extreme proportions. The giant Pacific octopus (Enteroctopus dofleini) has an average length of 16 feet, but some rare individuals can grow almost twice as big. The southern giant octopus (Enteroctopus magnificus), native to South Africa, can grow up to 6 feet in length while the giant Antarctic octopus (Megaleledone setebos) can measure 3 feet and the big blue octopus (Octopus cyanea) rarely reaches 1 foot.
Also called umbrella octopuses, members of the family Opisthoteuthidae live near the ocean floor, and generally do not grow bigger than 1 foot in length. However, some members of the genus Grimpoteuthis discovered in the last decade can reach up to 6 feet in length. Grimpoteuthis are also called Dumbo octopuses, because they have big ear-like fins.
The seven-arm octopus (Haliphron atlanticus) is the only member of the family Alloposidae. Found across the Atlantic, Indian and Pacific Oceans, this octopus can grow up to 13 feet in length and weigh 160 lbs. It has short arms in relation to its body length. Like in other octopus species, males have one of their eight arms modified for using during egg fertilization. It is called seven-arm octopus because in this species the adapted arm is coiled inside a sac.
Also known as blanket octopuses, members of the family Tremoctopodidae have transparent webs connecting the four dorsal arms of females. The four arms that are not webbed are much shorter than the dorsal ones. Most species show
extreme differences between males and females. While females can grow up to 8 feet, males are often only a few inches long and die after mating.