Orthoceras Straight Shell Specimen - 500 Million Year Old Cephalopod Fossil

Polished Orthoceras Fossil from Morocco

Size:  138mm x 50mm Approximately

Weight:  171gram

Orthoceras fossils are found all over the world.  They lived that lived from the Ordovician Period to the Triassic Period (500 200 million years ago).  These specimens come from near Erfoud, Morocco.  Orthoceras is a commonly used name for straight shelled nautiloids.

They are cephalopods, related to modern squid and octopus.  The segmented body and the septa that separates each segment.  These animals used their siphuncle to control their buoyancy and therefor their depth in the water. The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk.  The cephalopod increases the saltiness of the blood in the siphuncle and the water moves from the more dilute chamber into the blood through osmosis.  Cool trick!!

These animals grew their own shells and could grow up to 4 meters.  They were hunters that could eat anything from from plankton to unsuspecting trilobites.  They were were very intelligent creatures and moved around with jet propulsion.