Ancient Dinosaurs Likely Supplemented Their Diets With Washed Up Seaweed

New evidence suggests that the diets of Cretaceous dinosaurs were far more connected to the ocean than previously believed. By analyzing the chemical signatures trapped within fossilized teeth and bones, researchers have discovered that coastal-dwelling dinosaurs likely supplemented their nutrition by scavenging marine resources, much like modern animals that forage along shorelines today.

Tracking Carbon Isotopes Through Ancient Food Webs

The study, published in Frontiers in Ecology and Evolution, utilized isotope analysis to reconstruct these prehistoric eating habits. Plants naturally contain varying ratios of light (C-12) and heavy (C-13) carbon isotopes, a signature referred to as δ13C. When an animal consumes food, this isotopic “fingerprint” is integrated into the minerals of its bones and tooth enamel.

In modern terrestrial ecosystems, there is a predictable, modest shift in δ13C values between what an animal eats and what is deposited in its enamel. However, paleontologists have long been puzzled by the unusually high δ13C values found in dinosaur teeth. These levels were significantly elevated compared to what would be expected for a strictly terrestrial diet, hinting that these creatures were incorporating a different source of carbon into their bodies.

The Case for a Seaweed-Heavy Diet

Because the isotopic shift appeared across such a diverse range of animals, including dinosaurs, crocodiles, turtles, and fish, researchers concluded that marine matter—specifically washed-up algae—served as a vital dietary bridge. This behavior is a form of marine subsidization, where energy and nutrients from the sea are transferred to land, often providing a critical survival buffer when terrestrial food sources become scarce due to environmental stressors like drought.

Understanding Ancient Interconnectedness

This discovery underscores the complexity of Mesozoic ecosystems and reveals that the divide between marine and terrestrial habitats was more permeable than often depicted in the fossil record. By demonstrating that coastal dinosaurs relied on marine matter, the study highlights how oceanic stability directly impacted the health of land-dwelling populations.

“Our research clearly demonstrates that climate-driven extinctions in Mesozoic oceans would have had trickle-up effects in the terrestrial realm,” explained Lindsay Zanno, a study coauthor and paleontologist at the North Carolina Museum of Natural Sciences. Beyond simply defining what dinosaurs ate, the research provides a vital framework for understanding how ancient species responded to environmental change, offering a window into the ecological dependencies that drive biodiversity loss during periods of significant climate shift.