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Chemical signatures in fossilized teeth suggest coastal dinosaurs ate seaweed and other ocean foods more than 100 million years ago, researchers report. A study in Frontiers in Ecology and Evolution, led by geologist Dr. Clayton Forster of the University of Arkansas, examined fossils from former coastal sites along the Western Interior Seaway and the Gulf of Mexico shoreline, compared with inland sites, from the early Albian and early Cenomanian stages of the Cretaceous. Coastal fossils consistently showed higher carbon isotope values than inland ones, regardless of latitude or age, which ScienceDaily described as the first evidence of marine subsidization in prehistoric ecosystems. The researchers concluded that seaweed was the most likely source, since few other organisms fit the pattern, and Forster said coastal herbivores today commonly supplement their diets with seaweed. Tenontosaurus tilletti was an exception, with tooth enamel values resembling animals that eat only land plants.