Some nautiloid shells were curved, others straight. And not all nautiloids were swimmers. Some crawled slowly on the bottom of the sea. Though they are also fast swimmers, octopuses do not have hard shells to protect them from even faster predators. So they live on the seafloor, near the safety of rocks and coral reefs.
Octopuses also have a trick unknown to Nautilus .
They can squirt ink into the water, momentarily confusing a predator while the octopus escapes. Even more than Nautilus , octopuses have eyes that suggest intelligence. As scientists have learned, they are surprisingly intelligent. Another amazing soft-bodied cephalopod that is familiar in modern seas is the squid. There are many different species, some of which are the largest known invertebrates.