New Fossil Discovery Could Resolve Controversy Surrounding Spinosaurus Sailback Features

The fascinating debate surrounding the dinosaur Spinosaurus continues: was it an exceptional swimmer capable of diving to catch prey or a “hell’s heron” that snatched giant fish from shallow waters? Recent fossils of a new species, Spinosaurus mirabilis, discovered approximately 1,000 kilometers inland, may provide clarity, asserting that it resembled a sandpiper, as suggested by Paul Sereno from the University of Chicago.

The discussion of Spinosaurus lifestyles among paleontologists is ongoing, characterized by distinctive features such as large sails, massive claws, wide feet, and crocodilian jaws. Previous depictions in the 2025 BBC series Walking with Dinosaurs presented them as aquatic hunters.

In 2019, local guides led Sereno’s team to a remote Niger desert, where they unearthed a fragment of jaw bone identified later as belonging to a type of spinosaur. The COVID-19 pandemic delayed their return to the site.

During their second expedition, researchers discovered about ten Spinosaurus bones. Remarkably, they observed large crests atop the skulls and unique sails along their spines shortly after their initial find.

Sereno stated, “This was a shining moment because we recognized it as a new species of Spinosaurus that would significantly enhance our understanding of these dinosaurs.”

Named Spinosaurus mirabilis, this species is estimated to have roamed the Earth around 95 million years ago, growing to lengths of about 10 to 14 meters, comparable to the renowned Spinosaurus aegyptius. Sereno warned, “You wouldn’t want to be close to this animal; it could take you down in about three seconds.”

Similar to Spinosaurus aegyptius, this new species possessed a noticeable crest, though its crest was significantly larger—potentially reaching at least 40 centimeters in height for larger individuals. Researchers believe that, comparable to modern crowned birds such as the guinea fowl, these crowns were likely covered with a keratin sheath, standing at least 50 centimeters high.

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The delicate crest probably served not as a weapon but as a visual display. “It likely boasted bright colors,” Sereno remarked. “It signals, ‘I’m here, I’m healthy.’

The significant sails of the Spinosaurus might also have been utilized for visual signaling. Sereno suggests it raised questions about their purpose in mating and territorial protection. “Such environments, like beaches and riverbanks, enhance visibility, allowing animals to spot rivals and mates over long distances,” he explained.

Modern sandpipers, like the great blue heron, exhibit similar display characteristics, reinforcing the migration theory posited by Sereno. When comparing various animals based on the proportions of their jaws, necks, and hindlimbs, spinosaurids were found adjacent to heron-like species.

Although Spinosaurus struggled to swim efficiently due to its large sails, it could dive to depths of about 10 feet (3 meters) as an adult, according to Sereno.

Evidently, most spinosaur fossils have been discovered near oceans, while S. mirabilis thrived far inland. Sereno notes, “No marine predator weighing over a ton has entered freshwater habitats.” The absence of major freshwater predators, like river killer whales, supports the idea that these creatures were adaptations, similar to modern herons.

Sereno mentions, “This study validates the consensus developed regarding these animals. They aren’t super swimmers or deep divers; rather, they resemble herons and storks, foraging through shallow waters for their primary diet of fish.”

David Horn from Queen Mary University of London remarked, “The unique crest suggests a new species, and variations in jaws and teeth further solidify this point.”

Mark Witton at the University of Portsmouth, UK, emphasized that the lengths of the legs indicate Spinosaurus was capable of efficient movement, countering claims of a predominantly aquatic lifestyle.

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