Geisenoceras Fossil

Geisenoceras is an extinct cephalopod, similar to a squid with a long, pointed shell that lived during the Devonian period around 400 million years ago.

The lighter areas were cavities in its shell that it used for bouyancy and propusion in the water. The dark portion is the surrounding rock that the fossil was embedded in.

For many years, scientists thought this and many similar specimens were all one species called Orthoceras regulare.

But it was eventually discovered that there were in fact over 2,500 unique, conical-shelled, nautiloid species in the fossil record, and sorting the taxonomic record became quite an intensive undertaking.