by Brody Dymond
The Pachyteuthis densus was the fossil of a belemnite found in the Upper Sundance formation in Buffalo, Wyoming. Belemnites were a type of squid that lived many years ago.
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| Image of the Pachyteuthis densus study specimen. Photo date 2024 by B. Dymond. |
Belemnites evolved to have a different way of protecting themselves from other types of marine animals. They were fast swimmers! Instead of having an external shell, their shell was internal, which helped them speed through the water to escape from predators. The internal shell of a belemnite is the part that was fossilized. There are three parts of the internal shell: the pro-ostracum, the phragmocone, and the rostrum.
A group of belemnites was called a battlefield. The average size of the belemnites when they were alive was 30 - 50 centimeters long. Belemnites could be found worldwide in shallow waters close to the shore. Belemnites ate small fish, other marine animals, and possibly other belemnites.
The belemnite’s tentacles did not have suction cups like squid today. Instead, they had curved hooks. While squids today have eight arms, the belemnites had ten arms and on each arm were 30-50 curved hooks. They used the hooks on their arms to capture and eat small marine animals. While some squids today are the same size as belemnites, some squids can get much bigger. For example, Colossal Squid can get up to 14 meters (46 feet) long!
The Belemnites went extinct at the end of the Cretaceous Period roughly 65.5 million years ago. They died around the same time as the dinosaurs.
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| A concept of what Pachyteuthis densus looked like when it was alive. Artwork by B. Dymond. |
