Dinosaurs May Have Eaten Seafood Washed Onto Ancient Beaches, Fossils Suggest

Dinosaurs may have relied on food from the sea more often than previously thought, according to a new fossil study published on September 30, 2026.

Scientists found evidence suggesting that some dinosaurs living near ancient coastlines may have eaten marine material that washed onto beaches, including seaweed and other ocean-based food sources.

A Clue Hidden Inside Fossil Teeth

The discovery came from an unusual clue: carbon preserved inside fossilized teeth and bones.

Plants from the ocean generally contain different proportions of carbon isotopes than plants growing on land. When animals eat those plants, the chemical signature can become incorporated into their tissues and, eventually, their fossilized teeth.

Researchers analyzed carbon isotope patterns from fossils found at ancient coastal sites and compared them with fossils from locations farther inland.

Coastal Dinosaurs Had a Different Chemical Signature

The fossils from coastal environments showed higher carbon isotope values than fossils from landlocked environments.

The pattern appeared across several groups of animals, including dinosaurs, crocodiles, turtles and fish.

According to the researchers, the results suggest that marine resources were entering the coastal food chain and eventually reaching land-dwelling animals.

Seaweed May Have Been the Missing Ingredient

The researchers considered several possible sources for the marine signal. They concluded that seaweed and other marine plants are among the most likely explanations.

Storms can naturally wash seaweed and other marine material onto beaches. Modern coastal animals are known to take advantage of these temporary food sources, particularly when food on land becomes scarce.

The new study suggests that a similar process may have occurred millions of years ago.

Not Every Dinosaur Used the Sea

The researchers also found evidence that the behavior was not universal.

One dinosaur, Tenontosaurus tilletti, showed a carbon signature more consistent with animals that relied on plants growing on land.

This suggests that the marine signal was influenced by dietary choices rather than being a result of the geological process that preserved the fossils.

An Ancient Connection Between Land and Sea

The findings provide a new example of how closely connected marine and terrestrial ecosystems were during the Cretaceous Period.

At the time, a vast inland sea known as the Western Interior Seaway divided much of North America. The researchers studied fossils from former coastal areas along this ancient sea as well as sites near the ancient Gulf of Mexico.

Some of the fossils examined are between roughly 113 million and 96 million years old.

What the Discovery Reveals

The study does not mean that all dinosaurs ate seafood. Instead, it suggests that marine resources could sometimes supplement the diets of animals living near the coast.

Researchers say future studies will need to examine fossils from other regions and time periods to determine how widespread this behavior was.

The discovery adds another piece to the picture of ancient ecosystems, showing that the boundary between life on land and life in the sea may have been much less distinct than it appears today.

Sources

• Frontiers — “Dinos snacked on seafood washed up on ancient beaches, fossil study shows” — September 30, 2026.
• EurekAlert! — “Dinos snacked on seafood washed up on ancient beaches, fossil study shows” — September 30, 2026.
• Frontiers in Ecology and Evolution — “Marine Subsidization of Dinosaurian Ecosystems” — September 30, 2026.