The Architeuthidae are the largest known cephalopods, the largest known mollusks and probably the largest invertebrates ever known to exist in the oceans. Architeuthidae have been recorded as long as 60 feet in total length, most of the specimens that have been found are really in the 35-45 foot range. There are still many which range from about 20 to 30 feet in length. The total length includes the body, the head, the arms, and the two long feeding tentacles. These feeding tentacles are much longer than the rest of the body. The heaviest animals weigh about a ton, but most of the time they are a thousand pounds or less.
These giant squid also have the largest eyes out of any animal in the world. The eyes of the giant squid can be as big as a human's head. Most deep-sea animals have very large eyes so they can gather the small amounts of light that are available in the deep depths of the ocean. They might even be able to see bioluminescent light.
The Architeuthidae posses two tentacles that average about 10-12 meters in length. These tentacles have many suckers on the tips, called clubs. The tentacular clubs are narrow and have suckers, which are sub-spherical cups lined with sharp, finely serrated rings of chitin, in four longitudinal rows. These suckers cover only the inner surface of the arms and tentacles. These tentacular clubs are divided into distinct carpus, manus and dactylus. The manus has enlarged suckers along medial two rows. The suckers on the tentacles, and the arms, are not known to be any bigger than about five to five and a half centimeters. The carpal region has a dense cluster of suckers, in six to seven irregular, transverse rows.
The Architeuthidae also have fins that are proportionally small, ovoid, and without free anterior lobes. The fins at the rear of the mantle, are used to help the squid move by gentle, rhythmic pulses of water pushed out of the mantle cavity throughout the funnel.
They also have eight arms with suckers in two longitudinal rows. At the end of the arms they have a parrot-like beaks at the base. Another characteristic of the squid is that they have buccal connectives that attach to the dorsal borders of arms.
Giant squid contain the dark, sepia-colored ink that we associate with the smaller, more familiar squid.
They have the two, very large gills resting inside the mantle cavity. The squid are able to breath and move quickly by expanding the mantle cavity by contracting sets of muscles within the mantle. The water fills the expanded space, the muscles relax, and the elastic mantle then snaps back to a smaller size, jetting water out through the funnel. The jet of water closes the flaps on either side of the squid's head so water can exit only through the funnel.
The nervous system of the squids are very extensive and they even also have a complex brain. For this reason they are under extensive research. The circulatory system is closed which is a distinct characteristic of the squid.(Portner, et al 1994) (Forch 1998)