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A colossal, prehistoric reptile, the Deinosuchus, once preyed on dinosaurs. This ancient crocodilian possessed a broad snout reminiscent of an alligator but thrived due to a unique adaptation lacking in modern alligators: tolerance to saltwater environments. Delve into the fascinating world of this “terror crocodile” and its place in evolutionary history.
Deinosuchus: The Terror Crocodile That Conquered the Seas
Deinosuchus, meaning “terror crocodile,” was among the largest crocodilians ever to exist, possessing a body stretching nearly the length of a bus and teeth rivaling the size of bananas. Roaming North American rivers and estuaries approximately 82 to 75 million years ago, this apex predator featured a distinctive, broad, and elongated skull capped with a prominent bulge, a feature uncommon among other crocodilians. Fossil evidence, including tooth marks on Cretaceous bones, suggests Deinosuchus actively hunted or scavenged dinosaurs.
Despite its fearsome reputation, Deinosuchus was often referred to as a “greater alligator,” and previous evolutionary assessments aligned it with alligators and their ancestral kin. However, recent fossil analyses, combined with DNA evidence from extant crocodilians, propose a revised placement for Deinosuchus on the crocodilian evolutionary tree.
Published in the journal *Communications Biology* on Wednesday, scientists revealed that unlike alligatoroids, Deinosuchus retained salt glands—a characteristic inherited from ancestral crocodilians. These glands facilitated the regulation of sodium chloride, allowing it to thrive in saltwater environments. Modern crocodiles possess similar glands that serve the same purpose.
Salt Tolerance: The Key to Domination
Deinosuchus’s ability to tolerate saltwater proved advantageous, enabling it to navigate the Western Interior Seaway, which once bisected North America during a period of rising global sea levels. This unique adaptation allowed the terror crocodile to disperse across the continent and inhabit coastal marshes along the ancient inland sea and the Atlantic coast. Here are some key benefits of salt tolerance:
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- Facilitated movement across the Western Interior Seaway
- Enabled access to diverse habitats
- Provided a competitive advantage over less tolerant species
This new research presents groundbreaking insights into the climate adaptability of the crocodilian lineage, illustrating how certain species thrived in response to environmental cooling while others faced extinction. Salt glands empowered Deinosuchus to venture into territories inaccessible to its alligatoroid relatives, leading it to inhabit areas abundant with large prey.
Dr. Márton Rabi, a lecturer at the University of Tübingen and the senior author of the study, described the terror crocodile as “an absolutely monstrous animal,” emphasizing its dominance in marshy ecosystems. “No one was safe in these wetlands when Deinosuchus was around,” Rabi stated, estimating its total body length at roughly 8 meters (26 feet) or more.
Deinosuchus: Redefining Alligator Ancestry
Fossils of Deinosuchus have been discovered on both sides of the ancient seaway since the mid-19th century and are classified into at least two distinct species. The largest, Deinosuchus riograndensis, resided on the western side along the coast of an island known as Laramidia. This island, bordered by the Pacific Ocean, accounted for less than a third of North America’s landmass, while the remaining portion was known as Appalachia.
Unraveling the Puzzle of Distribution
The presence of Deinosuchus on both sides of the seaway has long perplexed scientists. If the giant reptile was indeed an alligator relative, which primarily inhabits freshwater habitats, how could it traverse a sea extending over 620 miles (1,000 kilometers)? A prevailing hypothesis suggested that early alligators possessed saltwater tolerance, a trait subsequently lost over time. However, limited evidence supported this theory, hinging primarily on the classification of Deinosuchus within the alligatoroid group, as Rabi explained.
Another explanation suggested that Deinosuchus dispersed across North America before the formation of the Western Interior Seaway. Nevertheless, fossil records contradict this speculation, with the seaway emerging approximately 100 million years ago, preceding the earliest known Deinosuchus fossils by roughly 20 million years.
To resolve these discrepancies, the researchers incorporated data from previously unanalyzed extinct crocodilians. These “missing links” facilitated the identification of previously unrecognized relationships between species and helped reconstruct the evolutionary timeline of specific traits.
“Our analysis found that saltwater tolerance is a fairly ancient trait of many crocodilians, and was secondarily lost in the alligatoroids,” Rabi stated. Dr. Evon Hekkala, a professor at Fordham University, noted that even a moderate tolerance for salt would have significantly benefited ancient crocodiles during climate-induced habitat transformations.
Hekkala, who was not involved in the study, asserted that “This ecological trait would have allowed lineages of crocodiles in the past to be more opportunistic in times when drastic environmental changes, such as sea level rise, were causing extinctions in less tolerant species.” This highlights the adaptability and resilience of terror crocodiles in the face of significant environmental change.
The Revised Crocodilian Family Tree
The research team also developed a revised crocodilian family tree by incorporating molecular data from modern crocodilians, allowing them to delineate the distinguishing characteristics shared by all alligatoroids. The findings revealed that early alligators were considerably smaller than contemporary crocodilians. Only after a climate shift and the extinction of other species, around 34 million years ago, did alligators develop larger body sizes. When alligatoroids emerged, the prodigious size of the terror crocodile was particularly striking.
The diminutive size of early alligatoroids served as additional evidence that the massive Deinosuchus was not a “greater alligator” but had, in fact, diverged onto a distinct branch of the family tree before the evolution of alligatoroids.
The study’s integrated approach, combining morphological analysis with a cutting-edge molecular tree to comprehend the evolution of Deinosuchus, offers a more precise depiction, according to Hekkala. “This new paper really reaches into both the evolutionary and ecological role of this amazing animal,” she concluded, pointing out how moving terror crocodile away from alligatoroids “fits much better with our current understanding of ecological flexibility among the extinct and living crocodiles.”
Deinosuchus was one of the largest crocodilians that ever lived, but it was not alone. Massive crocodilians evolved independently in aquatic ecosystems more than a dozen times over the past 120 million years, encompassing diverse climatic phases, including ice ages, as the study indicates. Reports of living crocodilians measuring 23 feet (7 meters) or more persisted until the 19th century, suggesting that enormous apex predators, such as the terror crocodile were more common than previously understood.
“Giant crocs are more like the norm – of any time,” Rabi said. The enduring legacy of terror crocodiles underscores the significance of ecological adaptability as a driving force in the evolution of these remarkable reptiles.