Blog Orthoceras Plaque
Fossil Information Sheet F012


Orthoceras Plaque
Orthoceras means "straight horn" and refers to a particular genus of European and North African nautiloid arthropod that existed from the middle Ordovician or Lower Silurian period to the Devonian Period (between 470-360 million years ago).

Orthoceras and Goniatite Fossilised Orthoceras are recognised by their elongated rocket or space-ship like cylindrical spear shapes, varying in size from a few centimetres long to more than 3 metres (9 feet).

They differed from other cephalopods in that they grew this straight, rather than coiled, shell, but like other cephalopods swam using a jet propulsion system.

Image from Wikimedia Commons They were amongst the most advanced invertebrates, having eyes, jaws, and a sophisticated nervous system. They also had tentacles and ink sacs much like a squid. Their life cycle was somewhere in the region of of 1 to 6 years, with most living from 2 to 4 years. They fed on Plankton, sea lillies and other smaller orthoceras!

Fossilised Shoal of Orthoceras
A large deposit of Orthoceras can be found in North Africa. As they died hundreds of millions of years ago their shells accumulated in great numbers upon the sea floor where they were aligned by currents, buried by sediments and transformed into stone over the ages. Today this particular pre-historic sea floor is found in the Atlas Mountain Range in Southern Morocco at the northern fringe of the Sahara Desert !

Other areas where Orthoceras fossils are found include the Americas, Asia and Europe. The Baltic island of Oland off the Swedish Coast has also many quarries yielding such fossils.

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