Curio

State Library of New South Wales
Nautiloid fossil

Nautiloid fossil

c400 million years ago

Set within the black marble skirting just to the right of the door leading into the Dixson room, under the fire extinguisher, is the oldest object in the library – a fossilised Orthoceras nautiloid which dates to the Silurian period of the Paleozoic era, approximately 400 million years ago. The name means ‘straight horn’ and refers to the long, straight conical shell. An ancestor of the modern squid, the Orthoceras nautiloid could grow up to 6 metres in length, and moved through the water backwards with air trapped inside its shell to keep it afloat.

From the 2500 known species of fossil nautiloids, only a handful of species survive today.

Nautiloid fossils are most commonly found in limestone.

Orthoceras nautiloid fossils are found all over the world. Some of the best examples have been found in the Jenolan Caves in NSW.

Orthoceras nautiloids were savage predators and fed on crustaceans. When they were hunting, they moved backwards through the water.

Ranging in size from 1 cm to 6 metres, nautiloids were free swimming animals with a head, two eyes, and arms or tentacles. They moved through the water backwards by a type of jet propulsion, with air trapped inside their shell to keep them afloat.

The black marble used throughout the Mitchell Wing was quarried in Yass.