New fossils may settle debate over enigmatic spinosaurs with sails

Were the mysterious dinosaurs known as spinosaurs excellent swimmers who could dive to catch prey? Or were they “herons of hell” plucking huge fish from shallow waters? Fossils of a new spinosaurus species that lived about 1,000 kilometers inland should settle the debate, according to its discoverers, confirming that it was a wading bird. “Coup de graceas far as I’m concerned,” he says Paul Sereno at the University of Chicago.

The lifestyle of spinosaurs has been a controversial topic among paleontologists, as the animal has a peculiar combination of features, including a large sail, huge claws, wide feet, and crocodile-like jaws. In 2025 BBC series Walks with dinosaurs he depicted them as aquatic hunters.

In 2019, a local guide took Sereno’s team to a remote desert site in Niger, where they found fragments of jaw bones that they later realized belonged to some species of spinosaurus. Due to the covid-19 pandemic and the remote location of the site, it took years before they could return.

On their second trip, Sereno and his colleagues found the bones of about 10 individual spinosaurs. Within hours of the first finds, the team realized that these spinosaurs had a large crest on their heads in addition to the characteristic sail on their backs.

“It was a wonderful moment because we knew this was a new spinosaurus, something that would have a big impact on how we understand this animal,” says Sereno.

A new species, named Spinosaurus mirabilislived about 95 million years ago and grew to about 10 to 14 meters in length, the team estimates – almost as big as the most famous spinosaur, Spinosaurus aegyptiacus. “I wouldn’t want to be near this animal because it would kill a person in about 3 seconds,” says Sereno.

S. aegyptiacus it also had a crest, but that of the new species is much larger – the bony part of the skull crest would be at least 40 centimeters high in large individuals. Based on comparisons with modern birds with crests, such as the helmeted guinea fowl, the team believes the bone would likely have been covered in a keratin sheath, so the crest would have been at least 50 centimeters high.

The comb is too fine to be a weapon of any kind. “It was probably brightly colored,” says Sereno. “It’s meant to be, ‘I’m here, I’m healthy.’

Spinosaurs’ large sails are also thought to have been for visual display, he says. “So these animals are really on display and the question is why?”

The answer could be that spinosaurs hunted along rivers where they needed to defend territory. “The proliferation of visual stimuli in environments such as beaches or riverbanks tends to be exaggerated because there you can look for a mile without obstruction and see your competitor or your mate much more easily than [in] a typical terrestrial environment,” says Sereno.

Modern wading birds like the great egret are also extremely display-oriented, Sereno says, and other characteristics of spinosaurs also fit the wading hypothesis. When his team plotted the range of animals on a graph based on the relative length of the jaw, neck, and hind limbs, spinosaurs appeared alongside wading birds like herons.

“It can’t swim well because it has a huge sail that makes it very unstable in the water. But it can reach up to 10 feet.” [3 metres] of water as an adult,” says Sereno.

Then there’s the fact that it lived far inland, while most other spinosaurs were found closer to where the seas were. No marine predator weighing more than a ton has ever moved into fresh water, Sereno says. There are porpoises and dolphins, but no killer whales. “And so I think it all plays into the same story that these animals are mega-heron-type animals.”

“The paper really confirms a lot of the consensus that has been building for these animals,” he says David Hone at Queen Mary University of London. “They are not super swimmers or divers, but much more like a heron or a stork, wading into the water to catch prey, mostly fish.”

“I think it’s pretty convincing that this is a new species. If it was just a crest, it could be a variation, but there are also differences in the jaws and teeth,” says Hone.

“The fact that the legs were not particularly short or poorly muscled suggests that it was no less capable of walking and wading than any other predatory dinosaur,” he says. Mark Witton at the University of Portsmouth in Great Britain. “This does not bode well for swimming lifestyle designs, which are already struggling with questions about swimming stability and propulsion. Spinosaurus.“

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