Fossil Shows Carnivorous Conga Line As Shark Eats A Cephalopod Eating A Crustacean

What would the palaeontologists of the future find in your hand if you were committed to fossil record while clutching your last meal? Image credit: Klug et al, 2021. Swiss Journal of Palaeontology. © 2021 BioMed Central Ltd - Open Access, CC BY 4.0

One of the unfortunate things about becoming a well-preserved specimen is that it almost always entails dying under some pretty hectic conditions. The bog bodies of people who have either fallen or been dumped into peat bogs can be so well preserved that they get mixed up with recent murder victims (and turn out to be 1,600 years old), while CT scans of museum specimens have revealed Turducken levels of frog-eating fish eating fish-eating frogs. Particularly spectacular fossils can sometimes do more than give a snapshot of ancient creatures’ anatomies, sometimes revealing clues about their lifestyle. One such gem was recently described in the Swiss Journal of Palaeontology, which seems to suggest an ancient squid-like creature was eating a crustacean when it was itself predated on by a shark.

The unusual and magnificently insightful fossil has been identified as a pabulite by the authors on the paper – a word intended to convey that while they caught the meal in action, none of the “food” actually made it as far as the predators’ stomachs. Can you imagine dying just before getting to take a bite out of a delicious donut? Tragic stuff. Fossils that reveal predation events where the prey has made it into the digestive tract of their killer are called regurgitalites.

Usually, pabulites only have bits of the once-living creatures preserved in the fossil, meaning paleontologists are tasked with piecing together the picture from traces of the predation event. They’re something of a golden egg for paleontologists, as they demonstrate in the most obvious way possible what extinct species were feeding on when they roamed the Earth (and its oceans) millions of years before humankind’s emergence.

belemnite
The belemnite arm holding remains of crustacean. Image credit: Klug et al, 2021. Swiss Journal of Palaeontology. © 2021 BioMed Central Ltd - Open Access, CC BY 4.0

This particular pabulite went a little further, being found to contain the belemnite (a squid-like cephalopod) Passaloteuthis laevigata from either the Early or Lower Jurassic period. Most of its soft parts are missing, but the animal’s arm crown is reported to be one of the best preserved ever found. The researchers say this finding is remarkable because it could indicate the belemnite remains were leftovers, dropped from the mouth of a predator. Evidently, it was a nourishing event all around, as within that magnificently preserved arm is an exuvia of a crustacean – meaning the belemnite was probably eating when it was eaten. An exuvia is the cast-off or sloughed-off skin of an arthropod. Not quite the decadent feast one might hope for as their last meal.

Labeled illustration of the fossil. Image credit: Klug et al, 2021. Swiss Journal of Palaeontology. © 2021 BioMed Central Ltd - Open Access, CC BY 4.0

It’s possible that the belemnite was ravaged by a predatory fish such as the ancient shark Hybodus hauffianus. That means that the belemnite was mere moments away from putting some of that sweet, sloughy skin in its mouth when it was rudely interrupted by becoming a snack itself, and we don’t mean the good kind.

Early Jurassic elasmobranch Hybodus hauffianus with its stomach clogged by belemnite rostra. Photo by R. Böttcher
Image credit: Image credit: Klug et al, 2021. Swiss Journal of Palaeontology. © 2021 BioMed Central Ltd  CC BY 4.0

“We suggest that this represents remains of a meal of a vertebrate predator, possibly of the Early Jurassic shark Hybodus hauffianus,” wrote the study authors. “This is remarkable, because it informs about the behaviour of a cephalopod and a vertebrate predator."

“Additionally, we use this occasion to introduce the term leftover fall for such remains of a meal and pabulite for the fossilized remains of which. Diverse pabulites have been reported before. They are valuable sources of palaeobiological information and deserve more attention.”


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