Harpoceras falciferum is the marker for the Falciferum Zone of the Lower Toarcian stage of the Upper Lias. Good specimens show beautiful ribbed ornamentation. Below is an identical specimen but from Whitby on the Yorkshire coast. We know that the rocks in both places (Seatown/Eype and Whitby) must be the same age because this ammonite species only existed for a brief period of geological time.
Find out more about ammonites on the molluscs pages.