Nautiloids

Nautiloids are animals that live in the sea. Their name is derived from nautilos (Greek) meaning a sailor. Aristotle wrongly believed that an argonaut (a type of nautiloid) used its arms as a sail, so was a sailor.

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Nautiloidea

Nautiloids are cephalopods. Living cephalopods include octopuses, cuttlefish and squid. Extinct cephalopods include ammonites and belemnites.

Size of stone: 40mm

The oldest nautiloids were the ancestors of all other cephalopods. Ammonites were descended from them. However nautiloids have outlived ammonites, since ammonites are extinct and some nautiloids are still alive today (see left). This modern nautilus has a spiral shell. Some of the fossils below show a straight shell.

Timescale: Nautiloids have been around for a long time, over 480 million years ago. There are still nautiloids alive today.

These straight shelled nautiloids are called Othoceras. They come from Morocco. They have been polished to show the structure of the nautiloids. Size of stones: 30mm (right) & 96mm (below)

A fossil nautilus
Size: 23mm