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Paleontologist Paul Sereno and an international team have named a new species of sail-backed predator, Spinosaurus mirabilis, from fossils pulled out of remote desert outcrops in Niger. The animal rivaled Tyrannosaurus rex in size and carried a tall, blade-like crest on its skull unlike anything seen on a spinosaurid before. Published in Science, the description represents the first new Spinosaurus species recognized in more than a century, rewriting assumptions about how many of these giant predators roamed North Africa during the Cretaceous.
Why a second Spinosaurus species changes the North African fossil record
Since Ernst Stromer named the original Spinosaurus aegyptiacus in 1915, researchers have debated whether a second spinosaurine species existed in the same Cenomanian-age rocks of North Africa. A 2016 study of quadrate bone anatomy argued that at least two spinosaurine forms were present, but the evidence fell short of a formal species description. Spinosaurus mirabilis fills that gap with diagnostic skull material, including the scimitar-shaped cranial crest that gives the animal its informal name.
The crest raises a question that goes beyond taxonomy. Its tall, laterally compressed shape sits at the junction of the skull roof and snout, a position that would have been submerged during any head-first strike into water. One testable reading is that the structure acted as a hydrodynamic stabilizer during shallow-water lunges, reducing lateral deflection of the skull the way a keel steadies a boat. That idea could be checked by running finite-element analysis on the crest and quadrate geometry and comparing the stress patterns against the morphofunctional dataset from the 2016 study. If the crest absorbed and redirected hydrodynamic loads rather than simply serving as a visual signal, it would add a functional dimension to spinosaurid diversity that no one has modeled.
From a decades-old book to the Jenguebi site
The trail to the new species began with a clue buried in a mid-twentieth-century French monograph. Sereno, a professor at the University of Chicago, traced a reference to a locality deep in the central Sahara and organized a 2019 reconnaissance trip to Niger. That initial survey identified promising exposures but did not produce the key fossils. The team returned with a larger crew and reached the Jenguebi site, where the crest element and skull pieces emerged during the 2022 field season.
The formal description, which appears in a Science article, places Spinosaurus mirabilis within a stepwise radiation of spinosaurids across the late Early and mid-Cretaceous. Rather than a single lineage that spread along ancient coastlines, the group appears to have diversified through successive ecological expansions. The inland location of the Jenguebi fossils supports that reading: this animal lived far from any reconstructed shoreline, suggesting spinosaurids occupied a broader range of habitats than coastal or riverine models predict.
The discovery supplies what the research team called the first indisputable evidence of a new Spinosaurus species in over a century. Stromer’s original Egyptian material was destroyed in a 1944 Allied bombing raid on Munich, leaving paleontologists to work from casts, drawings, and fragmentary finds for decades. The Niger fossils now provide a second anchor point for understanding how Spinosaurus-grade animals varied across geography and time. Additional anatomical details in the technical description emphasize differences in skull proportions, tooth spacing, and crest morphology that separate S. mirabilis from S. aegyptiacus.
Open questions about crest function and inland ecology
Several threads remain unresolved. The full morphometric dataset and body-mass calculations appear only in the paywalled supplement to the Science paper, so independent researchers have not yet been able to scrutinize the size comparison with Tyrannosaurus rex. Press materials describe the animal as T. rex-sized but do not publish the raw measurements needed to evaluate that claim on its own terms. Until those data are widely accessible, any statement about exact mass or length should be treated as provisional.
The age of the Jenguebi deposits also rests on stratigraphic correlation rather than new radioisotopic dates. Without independent geochronology, the placement of Spinosaurus mirabilis within the Cenomanian stage depends on the team’s reading of the local rock sequence and its similarity to better-dated sections elsewhere in North Africa. Future dating work could shift the animal earlier or later within the mid-Cretaceous, which would affect how the stepwise radiation model is calibrated and how closely S. mirabilis overlaps in time with S. aegyptiacus.
The broader debate over spinosaurid ecology, specifically whether these animals were specialized swimmers or shoreline waders, gains new texture from the inland Niger locality. A 2020 study in Nature described tail vertebrae shaped for propulsion through water, fueling the swimmer interpretation. But an animal living hundreds of kilometers from the nearest reconstructed coast complicates any model that ties spinosaurids exclusively to deep-water hunting. The crest’s possible hydrodynamic role, if confirmed by biomechanical modeling, would suggest that even inland populations used water in ways that shaped their anatomy, perhaps in shallow wetlands or broad floodplains rather than open marine settings.
Another layer of uncertainty involves the broader ecosystem at Jenguebi. The Science paper mentions associated fish, crocodile, and turtle remains, but the faunal list has not yet been fully synthesized into a paleoenvironmental reconstruction. If future work shows that large-bodied fish were abundant in perennial channels, it would bolster the view of Spinosaurus mirabilis as a fish specialist exploiting inland waterways. Conversely, evidence for strongly seasonal or ephemeral water bodies might push interpretations toward a more generalist predator that split its time between aquatic and terrestrial foraging.
The Niger fossils also intersect with a longer-running argument over how many giant theropods coexisted in mid-Cretaceous North Africa. Some researchers have proposed that spinosaurids, carcharodontosaurids, and abelisaurids partitioned prey and habitat to avoid direct competition. A second Spinosaurus species in roughly the same temporal window raises the possibility of niche partitioning within the spinosaurids themselves, perhaps with S. mirabilis favoring inland basins while S. aegyptiacus tracked coastal deltas. Testing that scenario will require more complete skeletons and better-constrained localities for both species.
Data access, collaboration, and future work
Absent from the public record so far are direct statements from Nigerien collaborators or permitting authorities. All published quotes trace to University of Chicago releases, leaving unclear how local scientists and institutions shaped the project on the ground. That silence does not imply a lack of involvement, but it highlights a recurring visibility gap in international fieldwork, where researchers from the country hosting the fossils often appear only in author lists rather than in press coverage.
Longer-term, the scientific value of Spinosaurus mirabilis will depend on how openly the underlying data are shared. The main article summarizes the diagnosis, but detailed measurements, CT slices, and digital models are essential for independent teams to test biomechanical claims about the crest and to refine phylogenetic analyses. A related entry in the biomedical index underscores how much of the technical content currently sits behind paywalls or in supplementary files that are difficult to access outside major research institutions.
Sereno’s team has indicated that additional material from Jenguebi remains under preparation, including postcranial bones that could clarify how the Niger species moved on land and in water. If those fossils confirm a robust, tail-powered swimmer with a stabilizing cranial crest, they would strengthen the case for a highly aquatic lifestyle that nonetheless extended far inland. Alternatively, evidence for more terrestrial limb proportions could revive arguments that spinosaurids were amphibious generalists rather than true aquatic specialists.
For now, Spinosaurus mirabilis stands as both a spectacular new species and a reminder of how incomplete the North African fossil record remains. A single locality, rediscovered from an old monograph and excavated over a few seasons, has doubled the named diversity of one of the most iconic dinosaur lineages. As more of the Sahara’s Cretaceous basins are mapped and systematically sampled, paleontologists expect additional surprises-perhaps further spinosaurids, or entirely new kinds of giant predators that will force yet another rewrite of the region’s deep-time history.
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*This article was researched with the help of AI, with human editors creating the final content.
