As ammonites evolved throughout the Mesozoic era, between 252 and 66 million years ago, their shell structures grew smaller, more tightly coiled, and more complex. Early ammonites had simple ...

Named in honour of St Hilda, Hildoceras bifrons is a type of ammonite that lived in the Early Jurassic Period. It is one of the most common ammonites present at Whitby. This example has a carved snake ...

Ammonoidea includes a more exclusive group called Ammonitida, also known as the true ammonites. These animals are known from the Jurassic Period, from about 200 million years ago. Most ammonites died ...