Dinosaurs living near the coasts may have incorporated resources from the sea directly into their diet.
About 100 million years ago, a vast inland sea split North America in two. Its shores were home to dinosaurs, crocodilians, fish, and many other animals. Researchers wanted to know whether this proximity to the ocean also influenced what they ate.
The world during the Cretaceous
Image Wikimedia
To find out, the team analyzed the enamel of fossil teeth from several regions of the United States and Canada. Enamel preserves part of the chemical signature of the food consumed by the animal. The researchers focused on two forms of carbon, whose proportions vary depending on the origin of the food.
Teeth discovered in ancient coastal environments contained more carbon-13 than expected. This difference sometimes exceeded 5.5‰ compared with the expected values. By contrast, fossils from an environment located far from the coast did not show this anomaly.
One explanation may lie on the beaches. Algae and certain marine plants have a different carbon signature from terrestrial vegetation. After a storm or with the tides, large quantities can wash ashore and become a food source for terrestrial animals.
Some herbivorous dinosaurs may therefore have eaten these plants from the sea directly. This behavior would not be impossible: even today, terrestrial animals regularly exploit resources deposited along the coasts. Fossil traces had already revealed that large herbivorous dinosaurs of the Cretaceous sometimes consumed crustaceans.
Small animals ate the washed-up material and were then themselves eaten by predators. Step by step, nutrients from the sea could thus have found their way into a large part of the terrestrial food chain.
The team now wants to better measure the importance of these marine contributions according to the distance from the shore and the species studied. Future analyses may also look for this phenomenon in other coastal regions of the Cretaceous, to determine whether beaches were a regular food source for dinosaurs.