Nautiloidea, gen. indet.

A shelled cephalopod, related to the living Nautilus and, more distantly, to squid and octopus. The shell is divided by transverse walls into gas-filled chambers, with the animal living only in the last and largest one.

By adjusting the fluid in those chambers the animal controlled its buoyancy. Cephalopods appeared in the Late Cambrian and were the principal large predators of Palaeozoic seas.