THE ORTHOCERAS FOSSIL

The Orthoceras was an ancient mollusk that lived more than 400 million years ago. The name means straight horn, referring to its characteristic long, straight, conical shell. The Orthoceras shell is made up of two main segments: the siphuncle & the septa. The siphuncle is the line running down the center from head to tail. The septa are the short-curved lines that run across or side to side. The differences in composition of these shell parts allowed for differences in fossilization so the parts to be seen.  These straight shelled nautiloids ranged in size from less than a centimeter to more than 14 feet! The preserved shell is all that remains of this ancestor of our modern-day squid.

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