Saltwater power turned ancient terror crocodile into a dinosaur-eating giant

WORLDWIDE:

A colossal, extinct reptile that preyed on dinosaurs had a broad, alligator-like snout—but what truly set it apart was a feature modern alligators lack: the ability to tolerate salt water.

Deinosuchus was among the largest crocodilian species ever recorded, stretching nearly the length of a bus and armed with banana-sized teeth. Between 82 and 75 million years ago, this apex predator roamed the rivers and estuaries of ancient North America.

Its skull was both wide and elongated, capped with a distinctive bony bulge unseen in other crocodilians. Fossilised bones from the Cretaceous period bearing toothmarks suggest Deinosuchus fed on or scavenged dinosaurs.

Though its name means “terror crocodile,” Deinosuchus was long considered more closely related to alligators and was often nicknamed the “greater alligator.” Previous research grouped it with ancient and modern alligator species.

But fresh fossil evidence, combined with genetic data from living crocodilians proved that deinosuchus belong to the crocodilian family tree.

Scientists now say Deinosuchus was not an alligatoroid at all. Unlike its freshwater cousins, it retained the salt glands found in early crocodilians—organs that help regulate salt levels by excreting excess sodium chloride. These are still present in modern crocodiles but absent in today’s alligators.

This salt tolerance likely gave Deinosuchus a powerful edge during the Late Cretaceous, allowing it to move freely through the Western Interior Seaway—a vast inland sea that split North America during a period of high global sea levels.

The predator’s range may have extended across both sides of the ancient seaway, including coastal regions along the Atlantic.

The newly proposed crocodilian family tree provides deeper understanding of how some species adjusted to environmental changes while others vanished.

Thanks to its salt glands, Deinosuchus could colonise ecosystems that its alligator-like relatives could not. With access to coastal marshes filled with large prey, it became one of the most dominant predators of its time—an enormous reptile capable of feeding on nearly anything that crossed its path.

“When Deinosuchus was around, nothing was safe in these wetlands,” said Dr. Márton Rabi, the study’s senior author and a lecturer at the University of Tübingen’s Institute of Geosciences. “This was an absolutely monstrous animal—easily eight metres long or more.”

To build a clearer picture of crocodilian evolution, researchers incorporated fossil data from previously unsampled extinct species—key “missing links” that helped clarify long-misunderstood relationships. These additions allowed the team to track when certain traits, such as saltwater tolerance, first emerged within the group.

“Our findings show that salt tolerance is an ancient trait in crocodilians, one that was later lost in alligatoroids,” said study co-author Dr Márton Rabi.

This adaptation would have been especially useful as shifting climates altered landscapes, added Dr Evon Hekkala, a biological sciences professor at Fordham University, who was not involved in the research.

“This ecological advantage likely gave some crocodile lineages a better shot at survival during periods of major environmental change, such as rising sea levels,” Hekkala said.

The team also reconstructed the crocodilian family tree using genetic data from living species. Their analysis showed that early alligators were considerably smaller than other crocodilians of the time.

The evolution of the larger body sizes seen in today’s alligators only began around 34 million years ago, likely as a result of climate cooling and the extinction of their competitors.

At the time Deinosuchus lived, however, it stood out as a giant among much smaller alligatoroid relatives. This, combined with new insights into early dwarfism in the group, supports the conclusion that Deinosuchus branched off from the family tree before alligatoroids began to evolve.

“Giant crocs are more like the norm — of any time,” Rabi said.