Bostrychoceras – a turret-shaped ammonite

At the end of the Cretaceous Period, it was not only dinosaurs and pterosaurs that disappeared. Sea life also suffered, and cephalopods like this ammonite became extinct.

Most ammonites had a spiral-shaped shell, however some Cretaceous ammonites showed some interesting variations in shell form. The shell of Bostrychoceras was helical, and had an almost turret-like shape. Other Cretaceous ammonites showed even more unusual shell forms. This diversity came to an abrupt end at the mass extinction event at the end of the Cretaceous.