A few weeks ago I wrote about how mosasaurs deftly cracked into the coiled shells of ammonites. The immense, seagoing lizards had a well-honed technique for breaking open the outer defenses of cephalopods – more squishy ammonite meat, less hard shell pieces.

But what did ammonites eat? Even though their fossils are extremely common, much of what we know about ammonites comes from shells, or pieces of shell. We don’t find ammonite gut contents in the same way that we can pick apart the fossilized food scraps in the stomachs of their predators, such as mosasaurs. The best clues about ammonite diets come from occasionally-preserved jaws – similar to the hard beaks of modern octopus and