Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids than they are to shelled nautiloids such as the living Nautilus species.
In the episode, "Cruels Seas," a group of Ammonites were brought to the park from Late Jurassic Europe, 149 million years ago. They reside in the Primeval Aquarium Enclosure.
In the Series 2 finale "Death of a Dynasty: To Hell... And Back", another group of Ammonites brought to the park from Late Cretaceous Montana, 65 million years ago.