Plesiosaurs vomited in river deltas, study reveals

New research published by Cambridge University Press has uncovered evidence that plesiosaurs, the long‑necked marine reptiles of the Mesozoic, frequently entered river deltas to expel indigestible material from their meals. The study, which analyzed fossilized gastrolith patterns and coprolite deposits, shows that these reptiles disgorged shells and other hard remains in a manner strikingly similar to the regurgitation behavior observed in modern fur seals and marine crocodiles.

The team used isotopic signatures and wear patterns on recovered gastroliths to reconstruct feeding habits, concluding that plesiosaurs likely consumed a diet rich in shelled organisms such as mollusks and crustaceans. By venturing into deltaic environments—where freshwater and marine ecosystems intersect—they could expel the accumulated debris, a strategy that may have helped maintain digestive efficiency and reduce the risk of infection. This behavioral parallel to extant marine mammals and reptiles provides fresh insight into the ecological roles of plesiosaurs and the evolutionary pressures that shaped their feeding strategies.

These findings broaden our understanding of plesiosaur biology and highlight the importance of interdisciplinary approaches in paleontology. Future research will aim to refine the timing and frequency of such expulsion events, potentially revealing further connections between extinct marine reptiles and their modern counterparts.