일반명 : 직선형앵무조개화석(Nautiloid Fossil)
학명 : Orthoceras species
시대 : 실루리아기 (Silurian 420 Million)
Location : Sahara Desert, Morocco

The Southern zone of Morocco, which includes the beginning of the Sahara desert and the last mountains of the Atlas range, is a region very rich in Paleozoic fossils.

The fossiliferous sites show how this zone, from the Cambrian to Devonian period (from 600 to 300 million years ago), was occupied by a large marine basin. Among the most important fossils in this area we find the Orthoderatids, which are primitive Nautiloids provided with a conic straight or slightly curved shell, subdivided internally into segments. The shape of the shell allowed these organisms to maintain, during their movements, a horizontal position in perfect hydrostatic equilibrium.

These sea animals were obviously agile swimmers and ferocious carnivorous predators, and could reach remarkable dimensions or one meter or more. After the death of these Nautiloids, the shells were accumulated and covered by sediments. In this manner they fossilized and remained intact until today.