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a crustacean eaten by a belemnite bitten by a shark

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Imagine the scene: About 180 million years ago, a squid-like creature pounced on a lobster-like crustacean. As it begins to take care of its prey, a second predator, probably a shark, throws itself on the cephalopod to bite it. Evidence of this “threesome” has been found in Germany.

Ancient predator-prey relationships can be inferred indirectly by the presence of fossils found in the same areas, but sometimes paleontologists stumble upon more direct evidence.

In 2018, for example, a team from the University of Southern California (USC, United States) analyzed the trace of a shark tooth stuck in a vertebra from a pteranodon found in the Smoky Hill Chalk area in Kansas. We then imagined this huge pterosaur, 80 million years ago, hovering near the surface of the water before being surprised by the predator emerging from the depths.

More recently, paleontologists isolated a new example of ancient predator-prey relationships in a German quarry.

Threesome mortal

Researchers have indeed discovered a fossil of belemnite (ancient marine cephalopod) about 180 million years old accompanied by the remains of a lobster-like shellfish. According to them, the two creatures probably died together before sinking to the bottom of the water (fewer scavengers and weaker currents facilitate the process of fossilization). The question is: why?

The remains of the belemnite and its prey preserved. The softer parts of the belemnite have disappeared. Credits: Klug et al., Swiss J Palaeontol., 2021

After analyzes of these fossils, it emerged that the belemnite had also been the victim of an attack. Just as the cephalopod was about to start its prey, a much larger predator visibly entered, before tearing a piece of its soft body and fleeing. Why go away so quickly? Probably because cephalopods have tough rostrums, hard, sharp, hard-to-digest beaks.

A few years ago, the analysis of an ancient Jurassic shark, also discovered in Germany, had indeed isolated a whole bunch of belemnite beaks in his stomach that may have resulted in his death (the diagram below shows the blockage created in the stomach).

After some uncomfortable experiences, the authors suggest that ancient Jurassic predators have learned to only attack the soft parts of these creatures.

shark fossils
Credits: Klug et al., Swiss J Palaeontol., 2021

Probably a shark

Another question also arises: who was this formidable predator? According to paleontologists, it was probably not an ichthyosaur. Although fossils of these extinct marine reptiles suggest that they regularly preyed on Belemnites, the contents of their stomachs do not show any of these hard structures.

The fossilized stomachs of ancient sea crocodiles suggest that these creatures swallowed up all their prey. For the case that interests us, again, it does not stick. In reality, researchers would rather lean towards an Early Jurassic shark named Hybodus hauffianus. At that time, these fish, up to two meters long, roamed shallow seas around the world.

A possible scene involving the three creatures is shown below.

shark fossils
The shark attacks the belemnite, itself taking care of its prey. Credits: Klug et al., Swiss J Palaeontol., 2021

Details of the study are published in the Swiss Journal of Paleontology.



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