Ammonoid

Ammonoids are extinct marine animals that lived millions of years ago, during the Mesozoic Era, notably in the Jurassic and Cretaceous periods. They are closely related to modern squid and octopuses, belonging to a group called cephalopods. Ammonoids are recognized by their distinctive spiral shells, which can vary in size and shape. These shells are often found as fossils and are useful for dating rock layers. Ammonoids thrived in oceans and went extinct around 66 million years ago, likely due to the same mass extinction that affected dinosaurs.