Meet Deinosuchus: A prehistoric 'terror crocodile' that once hunted dinosaurs and dominated Earth

Unlike alligatoroids, Deinosuchus kept ancestral salt glands. These glands help expel excess salt from the body. Crocodiles still have them, but alligators do not. That trait likely helped the predator survive the Western Interior Seaway. This seaway split North America during a period of high sea levels.

Salt tolerance helped Deinosuchus spread across the continent. It reached coastal marshes on both sides of the inland sea. It even lived along the ancient Atlantic coast. That ability gave it access to ecosystems filled with prey.

“This was a monstrous animal,” said Dr Márton Rabi. He is a lecturer at the University of Tübingen in Germany. “No one was safe in these wetlands when Deinosuchus was around.” Rabi told CNN that it could grow over 26 feet long.

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Rethinking Its Place in History
Fossils of Deinosuchus were found on both sides of the seaway. They belong to at least two distinct species. The largest was Deinosuchus riograndensis, which lived on Laramidia. Laramidia was an island on the seaway’s western side. The eastern side was called Appalachia.

The animal’s distribution confused researchers for decades. Alligators live only in fresh water. If Deinosuchus was an alligatoroid, how did it cross saltwater? Some thought early alligators had salt tolerance but lost it later. But no evidence supported that theory.

Others believed it spread before the seaway formed. However, the seaway existed 20 million years before the earliest Deinosuchus fossils. “The picture wasn’t very coherent,” Rabi said.

The new study added missing fossils to the family tree. These links helped scientists trace traits across crocodilian history. It also restructured how these ancient reptiles evolved.

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Salt tolerance, they found, is an ancient crocodilian trait. Alligatoroids later lost this trait. Having some salt tolerance helped species survive environmental change, said Dr Evon Hekkala. She’s a professor at Fordham University in New York. Hekkala was not involved in the study.

“This trait made crocodiles more flexible,” Hekkala said. It helped them adapt when sea levels changed and habitats shifted. Species without this ability likely died out.

A Misunderstood Giant
The team also built a new crocodilian family tree. They used modern DNA to study ancient traits. Early alligators were much smaller than other crocodilians. They only began growing larger after 34 million years ago. That’s when the climate cooled and competitors went extinct.

Deinosuchus, however, was always massive. That made it stand out from other alligator-like creatures. This suggests it evolved separately from true alligators. Rabi believes it split off before alligatoroids developed.

The study combined DNA and body shape analysis. This approach revealed how the terror crocodile evolved. Hekkala says it reshapes how scientists understand crocodilian adaptation. “It explains how these animals responded to climate change,” she said.

Deinosuchus wasn’t the only giant in history. Huge crocodilians evolved many times in the past 120 million years. They thrived even during ice ages. Some reports from the 19th century mention crocs over 23 feet long. “Giant crocs are more like the norm — of any time,” Rabi said.

This new research paints Deinosuchus as more than just a prehistoric monster. It was a survivor, a traveller, and a dominant force in its world. Its story reveals not just what it ate, but how it conquered changing environments — one marsh at a time.