EduF466b Nautilus

3D Model

Nautilus (Nautilidae)

144×105×45mm

Lower Jurassic (Blue Lias, 199-183Ma)

Dorset, England

Nautiluses are often known as “living fossils”, because they have remained almost completely unchanged for hundreds of millions of years and are the sole survivors of their order. They are a kind of cephalopod, like squids, octopi and cuttlefish, and unlike most cephalopods except the extinct ammonoids, nautiluses have a hard, coiled shell which is divided into gas-filled chambers, with the most of the body tissue in the outermost chamber. By moving water into and out of these chambers using a tube, or siphuncle, the animal can control whether it floats or sinks.

Some of the chambers are still empty, while some have become filled with sediment or crystals of the mineral calcite, which grew after death from liquid that filled the chambers.

Unlike ammonites, being relatively unchanged for so long means it is difficult to tell when a particular nautilus lived from how it looks like.

See: EduF127b Ammonite