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Fossilized vomit discovered near a Norwegian gas field reveals that Jurassic plesiosaurs swam into river deltas to expel hard, indigestible skeletal remains. According to paleontologist Dr. Dirk Knaust, the ancient marine reptiles traveled to shallow coastal waters to clear out compacted mollusk shells and exoskeletons after grazing on the seafloor.
Fossilized Puke in Offshore Drill Cores
More than 20 clumps of fossilized vomit—ranging in size from a walnut to a mango—were uncovered during drilling for an offshore carbon dioxide storage site near Norway’s Troll gas field. According to Phys, these specimens date back around 160 million years to the Jurassic or Early Cretaceous period. Paleontologist Dr. Dirk Knaust, who is employed by Equinor ASA, analyzed the regurgitalites to piece together the feeding and purging habits of these long-necked marine reptiles.
These ancient piles of sick survived the destructive forces of waves and tides because they were heavily compacted and coated in mucus. While most pellets were broken up, some clusters were quickly covered by river sediments or ended up in crustacean burrows on the seafloor, where they fossilized.
Decoding the Diet of Cryptoclidid Plesiosaurs
The contents of the regurgitalites offered a clear window into what these creatures consumed. Knaust identified bivalve shells, serpulid shells built by filter-feeding worms, crinoids, and belemnites. This specialized mix pointed to an animal designed to eat hard-shelled and exoskeletal prey from the seafloor.
Because plesiosaurs could not crush shells with their teeth, their stomachs compacted the skeletal material into pellets for oral rejection. The sheer size of the vomit clumps—reaching 10 centimeters (4 inches) or more—eliminated smaller predators like fish and cephalopods as culprits. Sharks and crocodiles of the Jurassic period hunted fish rather than grazing the seafloor for shellfish, leaving cryptoclidid plesiosaurs as the prime match.
The plesiosaur most closely matches the size and feeding profile of the vomit producer.
Dr. Dirk Knaust, Paleontologist
Why Swim Ashore to Vomit?
A puzzling aspect of the discovery is its location. The fossils were found in river deltas roughly 31 miles (50 kilometers) off the Norwegian coast, where the constant influx of fresh water would have made it impossible for the saltwater-dependent shellfish to live in large numbers.
To solve the mystery, researchers concluded that the plesiosaurs consumed the shellfish in deeper, saltier waters before swimming inland. The animals likely came close to shore to relax or sleep after hunting. This behavior mirrors modern-day fur seals and marine crocodiles. However, unlike seals and crocodiles that haul out onto beaches, plesiosaurs likely remained submerged in shallow delta waters because of their immense weight and body shape.
Dinosaurs on the Delta Lands
The coastal shallows were far from empty. Two-legged predatory dinosaurs and long-necked herbivores roamed the adjacent delta lands, leaving behind footprints that Knaust and his colleagues identified in some of the extracted drill cores.
This terrestrial presence meant that even if plesiosaurs had wanted to drag their heavy bodies onto the beach, the land environment posed significant dangers from roaming dinosaur predators.
A Hidden Record Across European Coastlines
Cryptoclidid plesiosaurs grew between 4 and 8 meters (13 to 26 feet) long—with the broader plesiosaur group spanning 2 to 13 meters (6.6 to 43 feet)—and survived for more than 140 million years across multiple extinction events from the Middle Jurassic to the Early Cretaceous (approximately 174–100.5 million years ago). While their skeletons have been recovered globally, the United Kingdom remains a particular hotspot.
During the Jurassic period, the Norwegian well site and the rock outcrops along southern England’s Jurassic Coast belonged to the same narrow sea, comparable to today’s North Sea. This geographic link suggests that Britain’s coastal cliffs may hold many more fossilized plesiosaur vomit deposits waiting to be uncovered.