Mollusks with spiral shells

A group of cephalopod molluscs with an external, chambered shell that is either straight or coiled. Nautiloids were very diverse in the past but only a single genus, Nautilus (the pearly nautilus), survives at the present day.

Nautiloids are primitive, thick-shelled, carnivorous marine invertebrates, cephalopod. The shell is divided into chambers. The nautiloid head has well-developed eyes and tentacles that can grasp prey. They swim by jet-propulsion; they squirt water out from the body cavity. They evolved during the Silurian and are still around today, but are uncommon (only a single genus survives). They were most abundant during the Paleozoic Era, roughly 400 million years ago. Some Nautiloids evolved into Ammonoids.