November - Ammonite
Ammonites are coiled relatives of the octopus (Cephalopods) and became extinct at the end of the Cretaceous Period around 65 million years ago.
Below is an image of a Harpoceras, which lived during the Jurassic Period. These fossils can be found in the Upper Liassic shale (Whitby Mudstone Formation) which crops-out widely across Cleveland and the Tees Valley. They lived in a warm tropical sea which occupied the area around 185 million years ago, alongside squid-like belemnites, marine crocodiles, ichthyosaurs, and long-necked plesiosaurs all of which have been discovered locally.
Ammonites reached their evolutionary zenith in the Jurassic and a great number of different short-lived forms existed during this Period. This resulted in fossils of each species being distributed in discrete bands within the rock record, a quality which geologists employ in correlating similar rock units across widely seperate districts.
