In February 2026, a new species of Spinosaurus, "Spinosaurus mirabilis", was described. It is a theropod excavated during surveys in the inland Sahara Desert of Niger in 2019 and 2022.
This new species, which casts a new stone into the century-long debate over Spinosaurus morphology, possesses the following characteristics:
- Giant cranial crest: A "scimitar" shaped crest about 50 cm high, one of the largest among non-avian dinosaurs.
- Inland habitation: Adapted to an inland river ecosystem hundreds of kilometers away from the coastline of the time, rather than the traditional coastal areas.
- "Hell Heron": Proposal of a new predation model of ambushing prey in the shallows like a modern blue heron, rather than diving.
On this page, we will explain in detail the unique anatomical features of this "amazing Spinosaurus" and the latest paleoecological model research regarding its semi-aquatic adaptation, which has been a mystery for many years.
Introduction: A New Horizon in Spinosaurus Research
In the history of dinosaur science, few taxonomic groups have seen their true image change and sparked as much fierce debate as Spinosaurus. The type species, Spinosaurus aegyptiacus, first described by Ernst Stromer in Egypt in 1915, suffered the tragedy of losing its type specimen to the flames of World War II. Since then, every time new fossils have been discovered from the Kem Kem beds in Morocco and elsewhere in the 21st century, its morphological reconstruction has been dizzyingly updated: from a bipedal terrestrial predator, to a semi-aquatic animal close to a quadruped, and even to a fully aquatic "underwater monster" that swam using its tail for propulsion.
Then, in February 2026, the discovery of the new species Spinosaurus mirabilis, announced by an international research team led by Professor Paul Sereno of the University of Chicago, brought a decisive turning point to this century-long quest. Yielded from strata in the central Sahara Desert of the Republic of Niger, hundreds of kilometers inland from the coastline, this new species not only established itself as the second species in the genus Spinosaurus, but also presents crucial evidence for elucidating the ecological adaptation and phylogenetic evolution process of the group.
Discovery and Excavation Process: Record of the Niger Expedition
The discovery of Spinosaurus mirabilis was not a product of coincidence, but the result of a tenacious investigation following a slight clue from decades ago.
Tracking from Historical Fragments and the Guidance of the Tuareg
The starting point of the investigation was a monograph by French geologists from the 1950s and 60s. It contained just a single line stating that "saber-like teeth" similar to those of Carcharodontosaurus were discovered at a specific point in the Niger desert. Professor Paul Sereno focused on this description, and in 2019, he stepped into the unexplored lands of Niger.
During the expedition in November 2019, the team met a local Tuareg guide, Mr. Abdul Nasser. He guided the team to a site where giant bones were exposed, an area later named "Jenguebi". Initially, the team could not fully understand the oddly shaped skeleton exposed on the surface, and temporarily withdrew after recovering only a few teeth and jaw fragments, as well as the base of a "crest" that would later prove to be important. However, the moment they examined the 3D digital model created at the camp, they were convinced that they were facing a new species of Spinosaurus with one of the largest cranial crests among non-avian dinosaurs, something they had never seen before.
Full-scale Excavation in 2022
After a few years of stagnation due to the COVID-19 pandemic, a full-scale expedition team of 20 members was reorganized in 2022. Through this expedition, fossils of multiple individuals, including a total of three well-preserved cranial crests, limb bones, and vertebrae, were recovered from Jenguebi and the nearby Iguidi. At this time, fossil specimens with a total weight of approximately 55 tons were transported out of Niger.
Geological Background: Paleoenvironment of the Farak Formation and Adaptation to the Inland
The fossils of S. mirabilis were buried in the Farak Formation, which was formed during the Cenomanian stage of the Late Cretaceous period (about 95 million years ago). This formation reflects the vast river networks and floodplains that spread across the inland of the African continent at the time, and consists mainly of sandstone and sandy shale.
The locality of Jenguebi was situated in an inland basin about 500 to 1000 km away from the coastline of the Tethys Sea at the time. This is in contrast to the fact that many of the Spinosauridae up to now have been discovered from coastal deposits. This geographical background indicates that Spinosaurus was ecologically extremely versatile, reigning as an apex predator not only in marine environments but also in inland freshwater river systems.
| Taxon | Specific Content and Significance |
|---|---|
| Theropods | In addition to Spinosaurus mirabilis, giant carnivorous Carcharodontosaurid dinosaurs were present. |
| Sauropods | Unnamed Titanosauriformes and Rebbachisauridae (two new species candidates). |
| Fish | Giant freshwater coelacanth Mawsonia, reaching 3.6 m (12 feet) in length. |
| Aquatic reptiles | Fossils of giant crocodiliforms and multiple turtles. |
| Plants | Geological evidence indicating a forest environment along the river. |
Anatomical Details and Definition as a New Species
The new species Spinosaurus mirabilis (meaning "amazing Spinosaurus"), as its name suggests, retains extremely unique traits.
Giant Cranial Crest (Scimitar Crest)
The most prominent autapomorphy of this species is the giant midline crest formed by the nasal and frontal bones. Viewed from the side, it has a "scimitar" shaped profile that curves sharply posterodorsally. The height of the crest skeleton itself reaches about 50 cm (20 inches), which is one of the largest among non-avian dinosaurs.
Surface Structure and Asymmetry:
Complex longitudinal and intersecting grooves, as well as countless microscopic vascular foramina, have been confirmed on the bone surface. This closely resembles the structures seen in the crests of modern cassowaries and guineafowl, suggesting that it was covered by a brightly colored keratinous sheath in life. Additionally, the crest is asymmetrically distorted in all three discovered specimens, potentially indicating the importance of individual differences and sexual display.
Specialized Dentition and Jaw Mechanism
The jaws of S. mirabilis have undergone ultimate evolution as a "fish trap" to efficiently capture slippery aquatic prey. It adopts a structure where the dentitions of the upper and lower jaws interdigitate, arranged to pierce the prey without gaps when the mouth is closed. Furthermore, the snout is relatively low, and when viewed from the side, the upper and lower margins are nearly parallel, which is a clear difference from S. aegyptiacus.
Physique and Limb Proportions
Most of the discovered specimens are subadults, but the total length of the subadult specimens is estimated to be about 8 m, and it is considered certain that adults reached 13 to 15 m in length and 6 to 8 tons in weight. Furthermore, according to the analysis of the preserved tibia, the hind limbs of this species may have been relatively longer compared to S. aegyptiacus, suggesting that it had a greater mechanical advantage in locomotion on land and in the shallows.
Phylogenetic Evolution: Three-Stage Radiation of Spinosauridae
Professor Paul Sereno and colleagues proposed a "Stepwise radiation" model that divides the evolution of Spinosauridae into three discrete phases by integrating the data of S. mirabilis.
- Phase 1 (Initial Divergence in the Late Jurassic): About 150 million years ago, they diverged from other Tetanurae and began to acquire a unique cranial morphology specialized for piscivory. At this stage, the divergence into the two major lineages of Baryonychinae and Spinosaurinae had already begun.
- Phase 2 (Pan-Tethyan Diversification in the Early Cretaceous): They rapidly expanded their distribution in the coastal areas around the Tethys Sea and became major predators of the ecosystem. Suchomimus in Africa and Baryonyx in Europe flourished during this period.
- Phase 3 (Specialization and Gigantism in the Late Cretaceous): During the Cenomanian, they grew to maximum sizes in North Africa and South America, possessing both giant sails and complex cranial crests. However, this unique radiation came to a sudden end toward the end of the Cenomanian due to rapid environmental changes.
"Hell Heron" Model: Redefining Paleoecology
The discovery of S. mirabilis strongly reinforced the "Shoreline ambush predator" theory proposed by Professor Paul Sereno and colleagues in the long-standing debate over the lifestyle of Spinosaurus.
Reevaluation of Bone Density and Buoyancy Control (Counterargument to the Diving Theory)
Previous studies argued that the extremely high bone density of Spinosaurus functioned as ballast, similar to diving animals like penguins, and was an adaptation for pursuing prey underwater. In response, Professor Sereno and colleagues have deployed the following counterarguments.
Terrestrial giants like elephants can also have similarly high bone density, and this does not necessarily mean aquatic adaptation. Furthermore, the 2-meter tall back sail would create enormous drag underwater, and the latest simulations have also shown that Spinosaurus could not dive stably underwater and was prone to capsizing.
Comparison with Modern Herons
Professor Sereno compares the elongated neck, powerful hind limbs, and jaw structure suited for piercing fish of this species to modern large herons (especially the great blue heron). It is thought to have adopted a style of standing firmly in shallow waters about 2 meters deep, and striking down like lightning at giant fish (such as Mawsonia) below the water surface from above. It is speculated that the giant, colorful cranial crest and the sail on its back were not tools for pursuing prey, but functioned as "billboards" for displaying presence to peers and for mate selection in the complex inland river environment.
| Comparison Item | Spinosaurus mirabilis | Modern Great Blue Heron |
|---|---|---|
| Main prey | Giant coelacanths, lungfish | Small fish, amphibians, insects |
| Habitat | Cretaceous rivers and floodplains | Modern wetlands, ponds, and rivers |
| Predation method | Ambush and strike in the shallows | Standing still and piercing |
| Ornamental structures | Giant cranial crest, back sail | Head plumes, decorative feathers |
Conclusion: Revolutionizing the Understanding of Cretaceous North African Ecosystems
The discovery of Spinosaurus mirabilis is a historic achievement that fundamentally rewrites our understanding of the Cretaceous North African ecosystem.
One of the largest "scimitar-shaped" cranial crests among non-avian dinosaurs and a highly specialized interdigitating dentition indicate that the ornamentation and feeding adaptation of Spinosaurus had reached their limits. Also, the discovery in the inland area 1000 km away from the coastline proved that this group had broad adaptive capabilities that did not rely on the ocean.
The "Hell Heron" model, which replaces the "Diving theory", provides a more consistent explanation from all aspects of morphology, geology, and statistics, and has elevated the debate on the semi-aquatic adaptation of dinosaurs to a new dimension. This "amazing" Spinosaurus, appearing for the first time in about a century, has once again made the world aware that many unseen tales of life still sleep beneath the desert sands.
References & Bibliography
- 'Hell-heron' dinosaur discovered in the central Sahara | University of Chicago News, https://news.uchicago.edu/story/hell-heron-dinosaur-discovered-central-sahara
- Bizarre Dinosaur With a Giant Sword-Shaped Crest Discovered During the 'Expedition of the Century' in African Desert - ZME Science, https://www.zmescience.com/science/news-science/spinosaurus-mirabilis-african-desert/
- Spinosaurus mirabilis: A New Scimitar-Crested Spinosaurus - FossilEra.com, https://www.fossilera.com/pages/spinosaurus-mirabilis-a-new-scimitar-crested-spinosaurus
- New 'scimitar-crested' Spinosaurus species discovered in the central Sahara | EurekAlert!, https://www.eurekalert.org/news-releases/1116589
- New Spinosaurus Species Discovered in Niger | Sci.News, https://www.sci.news/paleontology/spinosaurus-mirabilis-14571.html