The kraken's tentacles are used for catching animal and plant food. The trailing fibers with their hooks and stings are evolved from the suckers found on the tentacles of its ancestors. When the prey is caught it is passed to the mouth along the tentacles by muscular contraction.
The Kraken, Giganticeras fluitarus, is a massive, floating ammonite from open seas, somewhat similar to a floating siphonophore jellyfish, in The New Dinosaurs: An Alternative Evolution. The only other creature that can attack it is a pelorus.
The ammonites of the Mesozoic seas were mostly swimming animals that moved freely about in the ocean waters chasing small swimming creatures that they caught with their tentacles. In Cretaceous times they developed into a number of different forms. There were those with heavy shells produced in irregular coils, that spent their time crawling along the seabed. Others were freely drifting animals, filtering microscopic food particles from the water using very fine tentacles. This second trend has reached a pinnacle with the modern kraken.
The shell of the kraken is truly enormous, some specimens reaching 4 meters (13 feet) in diameter. The shell acts as a protective armor, as well as a float to keep the animal in the fertile surface waters. It has twelve tentacles that
The internal structure of the kraken is a 'scaled-up' version of the internal structure of any shelled cephalopod. The shell has a number of chambers, and the animal occupies the last one. As the kraken grows it produces more shell, moves forward and lays down a wall to create a new chamber behind. A blood vessel connecting all the chambers controls the air pressure and hence buoyancy. The twelve tentacles with their trailing curtain of stings and hooks, radiate from the mouth at the shells entrance.
it spreads out around itself, and each of these has thousands of trailing fibers that are armed with stings and hooks. The whole arrangement forms a deadly net that covers an area of about 20 meters (67 feet) in diameter. The kraken will eat almost anything that becomes entangled in its traps, from microscopic floating plants, to fairly large fish. Many krakens often drift in the same area of productive waters, their floating shells acting as perches for migrant birds and pterodactyloid pterosaurs.
The air-filled chambers of the kraken's shell mean that it floats with the living animal and the tentacles just submerged (a). It moves by expelling waste water through its syphon, propelling the shell backwards and allowing the tentacles to trail behind (b).