A New Giant From the Sahara Rewrites the Story of Spinosaurus

Deep in the central Sahara, led by a local Tuareg man on a motorbike into a landscape of towering dunes and fossil-studded rock, a team of paleontologists stumbled onto something that had not been seen in over a century — a new species of Spinosaurus. The bones they pulled from the desert surface in November 2019 were so strange and unexpected that the researchers initially didn’t know what they were looking at. It wasn’t until they returned in 2022, found two more specimens, and assembled the skull digitally on a laptop powered by solar panels in the middle of the Sahara, that the magnitude of the discovery registered.

“This find was so sudden and amazing, it was really emotional for our team,” said Paul C. Sereno, Professor of Organismal Biology and Anatomy at the University of Chicago and lead author of the study published February 19 in Science. “I’ll forever cherish the moment in camp when we crowded around a laptop to look at the new species for the first time.”

The new dinosaur, named Spinosaurus mirabilis — the species name meaning “astonishing” in Latin — is distinguished above all by a sweeping, blade-shaped bony crest that arches upward over the skull like a drawn scimitar. It is the tallest cranial crest ever recorded on any non-avian theropod dinosaur, exceeding in height the rest of the cranium at the orbits. In life, it would have been extended further by a sheath of keratin and was likely brightly colored, functioning as a visual display structure. The comparison to the helmeted guinea fowl (Numida meleagris), a living bird whose bony casque is extended by just such a keratinous sheath, is explicit in the paper’s imagery.

That connection matters. Spinosaurus mirabilis sits squarely within the long, strange bridge between non-avian dinosaurs and the birds alive today. Modern birds are avian dinosaurs — direct descendants of the theropod lineage that also produced Spinosaurus, Tyrannosaurus, and the small, feathered Velociraptor. The features that we associate with birds — cranial crests used for display, elaborate ornamentation, visual signaling — were not inventions of birds. They are ancient, deep-rooted traits in the theropod lineage that birds inherited and elaborated. The towering crest of S. mirabilis echoes what a cassowary carries on its head today, and for likely the same reason: to be seen.

The skull of S. mirabilis also features interdigitating upper and lower tooth rows, where the teeth of the lower jaw protrude outward between those of the upper jaw, forming an interlocking fish trap. This adaptation has appeared repeatedly across the history of vertebrate life — in the aquatic ichthyosaurs, semi-aquatic crocodilians, and airborne pterosaurs — and it sets Spinosaurus apart from all other dinosaurs as an extreme piscivore.

Beyond its anatomy, the location of the find carries enormous scientific weight. Until now, all Spinosaurus fossils had been recovered from coastal deposits near the margins of the ancient Tethys Sea. That fact had fueled a long and heated debate: was Spinosaurus a wading shoreline predator, or a fully aquatic pursuit diver that hunted fish underwater much as a penguin does? Proponents of the aquatic hypothesis, most prominently Nizar Ibrahim and colleagues writing in Nature in 2020, argued that the dinosaur’s paddlelike tail was adapted for underwater propulsion.¹ Sereno’s team had previously pushed back in eLife in 2022, arguing the skeletal evidence better supported a semiaquatic wading lifestyle.²

The discovery of S. mirabilis in an inland basin — some 500 to 1,000 kilometers from the nearest Cenomanian-era marine shoreline — now tips the scales decisively. All large-bodied secondarily aquatic tetrapods known from the fossil record, living or extinct, are marine animals. Finding a seven-tonne-plus Spinosaurus that far inland, buried alongside long-necked sauropod dinosaurs in river sediments, is powerful evidence that these animals were not aquatic divers bound to the sea.

“I envision this dinosaur as a kind of ‘hell heron’ that had no problem wading on its sturdy legs into two meters of water but probably spent most of its time stalking shallower traps for the many large fish of the day,” Sereno said.

To quantify that interpretation, the research team conducted a principal component analysis of body proportions — measuring skull dimensions, neck length, and hind limb length — across 43 living and extinct carnivorous archosaurs. Spinosaurids plotted between semiaquatic wading birds such as herons and aquatic diving birds such as darters, far from all terrestrial theropods and from short-limbed crocodylians. The analysis placed spinosaurid body form closest to that of long-legged wading predators, consistent with hunting fish in shallow water rather than pursuing prey in open water.

The paper also situates S. mirabilis within a sweeping new three-phase model of spinosaurid evolution. The first phase, spanning approximately 35 million years from the Jurassic into the earliest Cretaceous, saw the emergence of the elongate, fish-snaring skull and the fused median nasal crest that would define all later spinosaurids. During this phase, two distinct evolutionary paths diverged: the baryonychines, characterized by narrow gharial-like jaws and a profusion of small dentary teeth, and the spinosaurines, featuring broader posterior snouts with fewer, more spaced teeth. In a second phase during the Early Cretaceous, spinosaurids spread around the habitats bordering the Tethys Sea, becoming the dominant large predators of their ecosystems on both Gondwana and Laurasia. Well-known members of this phase include Suchomimus tenerensis from central Africa and Irritator challengeri from Brazil, the latter described in detail by a 2023 reassessment in Palaeontologia Electronica.³

The final phase — represented by S. mirabilis and its close relative S. aegyptiacus — lasted some 15 million years before a catastrophic end. Around 94.5 million years ago, a rapid global rise in sea level flooded low-lying continental areas across the Sahara, creating a shallow Trans-Saharan seaway and triggering marine biotic turnover. On land, the massive piscivores of the Spinosaurini appear to have gone extinct. Finding S. mirabilis in an inland basin, where no spinosaurid had previously been documented, establishes that these animals ranged far more widely in their final days than the coastal fossil record had suggested.

The Science editor’s summary captured the broader arc: the researchers argue that this group of dinosaurs underwent three phases of evolution with increasing aquatic adaptations and existence in habitats around the Tethys Sea.

The fossils are housed at the Musée National Boubou Hama in Niamey, Niger, where Sereno’s team is also working to build the Museum of the River — the world’s first zero-energy museum — to showcase Africa’s paleontological heritage for local communities and the world. Casts of the new skull and a touchable model of the scimitar crest will join an existing dinosaur exhibit at the Chicago Children’s Museum beginning March 1.

For a lineage that dominated predatory ecosystems across two continents for tens of millions of years, the story of the spinosaurids is remarkable — and now, with S. mirabilis, considerably richer.

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Endnotes

1. Ibrahim, N., et al. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature 581, 67–70 (2020). doi:10.1038/s41586-020-2190-3
2. Sereno, P.C., et al. Spinosaurus is not an aquatic dinosaur. eLife 11, e80092 (2022). doi:10.7554/eLife.80092
3. Schade, M., et al. A reappraisal of the cranial and mandibular osteology of the spinosaurid Irritator challengeri. Palaeontologia Electronica 26, 1–116 (2023). doi:10.26879/1242
4. Sereno, P.C., et al. Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation. Science 391, eadx5486 (2026). doi:10.1126/science.adx5486
5. University of Chicago Medical Center. New ‘scimitar-crested’ Spinosaurus species discovered in the central Sahara. EurekAlert! February 19, 2026. https://www.eurekalert.org/news-releases/1116589