Nautiloid

Taxonomy

Phylum: Mollusca

Class: Cephalopoda

Diagnostic features

Simple suture

Chambers

Central siphuncle

Straight, curved or coiled shell

Stratigraphic range

Cambrian to recent

Straight forms: Cambrian to Permian

Coiled forms: Devonian to Present

Way of life

Nektonic (jet propulsion)

Predatory

Buoyancy controlled by changing gas/liquid contents of chambers

Marine

Preservation

Commonly preserved as internal moulds

Modern nautiloids preserved with original shell material

Advanced notes

Nautiloids originated in the Cambrian period, and radiated during the Ordovician. These early nautiloids had conical shaped shells. In the Silurian some nautiloids used curved shells, and by the Devonian some were coiled. The evolution of the coiled shell from the straight is thought to be driven, at least in part, by increased mobility of a coiled shell compared to a long straight one.

Nautiloids could be confused with ammonoids. You can distinguish them by the location of the siphuncle and the complexity of the suture pattern. Nautiloids, unlike ammonoids, are not extinct, although only six species remain today (compared to thousands in the Palaeozoic). This means that if presented with modern shell material it is likely a nautiloid and not an ammonoid.

Specimens

Browse nautiloids

External links

Telling planispiral fossils apart