Orthoceras (ortho1)

Orthoceras were early cephalopods living in the early Palaeozoic era, over 400 million years ago. The Octopus like creatures lived in the outer chamber of their shell,  the other chambers being partly filled with gas to give neutral buoyancy. This and similar species were probably dominant predators of early seas, later
 being replaced with more manoevarable coiled forms like the Ammonites. This specimen is from the Anti Atlas mountains of Morocco. The total length o the rock is about 152mm and it weighs 335gm.