Dirk Knaust found more than 20 fossilized vomit pellets in an ancient river delta about 50 km off Norway’s coast, suggesting plesiosaurs ate shellfish in deeper water before swimming shoreward to expel hard remains. The study appeared in Geological Magazine.
The shellfish remains came from a delta with shifting freshwater salinity, unlike the stable ocean conditions the shellfish needed. Knaust ruled out fish, sharks and crocodiles based on the pellets’ size and prey mix, attributing them to cryptoclidid plesiosaurs, which grew 4–8 meters and lived about 174–100.5 million years ago.
Knaust said the reptiles may have approached shore to rest or sleep after hunting, and likely regurgitated then. Unlike seals and crocodiles, which haul out on land, plesiosaurs probably stayed submerged because of their weight and shape.
