The long-running debate over how spinosaurs—those bizarre, sail-backed dinosaurs—lived has likely reached its end. A newly discovered species, Spinosaurus mirabilis, found in an inland desert site in Niger, provides strong evidence that these predators were not deep-water divers but instead resembled enormous, prehistoric herons, stalking fish in shallow waters. The discovery settles a dispute that has divided paleontologists for decades: were spinosaurs aquatic hunters or wading specialists?
The Mystery of the Spinosaur Lifestyle
Spinosaurus’ anatomy has always been a puzzle. It possessed a large sail, massive claws, broad feet, and crocodile-like jaws—a combination of traits that suggested both aquatic and terrestrial behavior. Early reconstructions, like those in the 2005 BBC series Walking With Dinosaurs, depicted them as active underwater hunters. However, the new fossil challenges that notion.
Discovery in the Niger Desert
The fossil site was first identified in 2019 by a local guide working with Paul Sereno’s team from the University of Chicago. The remote location and the onset of the COVID-19 pandemic delayed full excavation for years. When the team returned, they unearthed remains from roughly ten individuals, all sporting a distinctive, large crest atop their skulls in addition to the familiar sail along their backs.
Spinosaurus mirabilis : A New Species
S. mirabilis lived approximately 95 million years ago and reached sizes comparable to the well-known Spinosaurus aegyptiacus, growing up to 10–14 meters long. The most striking feature of the new species is its crest, which could reach at least 50 centimeters high when covered in keratin. According to Sereno, “It was meant to say, ‘I am here; I am healthy.’” The crest, alongside the sails, likely served as a display feature for territory defense and mate attraction.
Wading Behavior Supported by Anatomy
The team’s analysis of jaw, neck, and limb proportions places spinosaurs firmly alongside modern wading birds like herons. Their anatomy—particularly the sail—makes efficient swimming unlikely. “It can’t swim well because it’s got this huge sail that makes it very unstable in water,” Sereno explains. The inland location of the fossils further supports the wading hypothesis, as no marine predator of this size has ever adapted to freshwater environments.
Expert Consensus
David Hone of Queen Mary University of London confirms the findings: “They are not super swimmers or deep divers, but much more like a heron or stork, wading into water to catch prey.” Mark Witton of the University of Portsmouth agrees, stating that the leg structure doesn’t support swimming adaptations.
The evidence is mounting: spinosaurs were not underwater predators but rather gigantic, display-oriented waders that stalked prey in shallow rivers and defended territories through visual signaling. The discovery of Spinosaurus mirabilis provides the most compelling evidence yet, bringing a definitive end to the debate over their lifestyle.
