Ammonites are an extinct group of marine molluscs, which died out during the Cretaceous-Tertiary Mass Extinction, 65 million years ago. Ammonites' closest living relatives are octopus, squid and cuttlefish.

Ammonites laid their eggs in a single batch at the end of their life. These, along with juvenile ammonites, would have been floating at the surface of the ocean when they were killed off by the effects of the meteorite impact.

It is thought that their modern relatives survived the extinction because they lay eggs on the sea floor and in smaller batches many times during their life