It’s a fish-eat-belemnite-eat-crustacean world. A pair of remarkably preserved fossils appear to record the aftermath of a dramatic confrontation in the prehistoric ocean, when one predator was in the middle of a meal only to be targeted by a bigger one.

“The fossil is amazing by itself” because of its state of preservation, says Christian Klug at the University of Zurich in Switzerland. But the remains tell a story that sheds light on who was eating who millions of years ago.

Klug and his team studied the fossils of two marine organisms from the dinosaur era, which were roughly 174 to 183 million years old. The remains were found in 1970 by a fossil collector called Dieter Weber in a quarry near Holzmaden in Germany. They have since been bought by the State Museum of Natural History Stuttgart.

One of the animals is a belemnite (Passaloteuthis laevigata), a cephalopod related to modern squids and octopuses. Belemnites had a bony guard on their tail ends, which are the most commonly preserved bits.

This belemnite had its bony guard, but it also had fragments of soft tissue and parts of the arms. Tangled up with the arms was a second fossil: a crustacean related to modern crayfish and shrimp from the genus Proeryon.

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Crustaceans shed their skin when they grow, and modern cephalopods like to eat the moulted skin. “They actually follow some crayfish so they can eat the moults,” says Klug. He says the belemnite was probably doing the same thing.

But the incompleteness of the belemnite, despite the overall superb preservation, suggests it didn’t complete its meal. Klug says a larger predator seems to have targeted it and eaten most of the soft body parts, discarding the bony guard.

It isn’t clear what ate the belemnite, but Klug suspects a shark called Hybodus hauffianus, which is known to have eaten belemnites. One specimen has at least 93 belemnite guards in its stomach, which may have killed it in a truly spectacular case of indigestion.

Klug suggests that most predators learned not to swallow the guards, choosing either to spit them out, vomit them up or just bite off the soft parts and ditch the rest. If a shark did that, it would explain why only those parts of the belemnite were preserved.

Journal reference: Swiss Journal of Palaeontology, DOI: 10.1186/s13358-021-00225-z