One of the natural predators to ammonites were the marine reptiles, particularly mosasaurs and elasmosaurs.
Mosasaurs, while robust predators, lived nearer to the ocean surface, preying on fish, turtles, birds, and sadly for this fellow, ammonites.
Ammonites were also prey to the elasmosaurs, a genus of plesiosaur that lived in the Late Cretaceous. With their long necks, the could move unseen in the depths then chomp down with their cage-like teeth to munch on fish and those unfortunate enough to be the tasty bounty of ancient times.
