Some ammonites had long, straight shells, while others had helix-shaped shells. Most species, however, had coiled shells lined with progressively larger chambers separated by thin walls called septa.

Ammonites' growing shells typically formed into a flat spiral, known as a planispiral, although a variety of shapes did evolve over time. Shells could be a loose spiral or tightly curled with whorls ...

Lyme Regis Museum geologist Paddy Howe, who was a technical adviser for Ammonite, describes Anning ... it is the specimen used to describe this species and that scientists still refer to it ...