A Second Species of Spinosaurus: Spinosaurus mirabilis
Recently described from 95-million-year-old (Late Cretaceous) rocks in Niger, central North Africa, Spinosaurus mirabilis is the first new species added to the genus in over 100 years.
Its fossils were found in ancient river deposits, showing that it lived in large freshwater river systems that once flowed through what is now the Sahara Desert. One of its most striking features is a tall, curved, scimitar-shaped crest on its skull, which may have been used for display or species recognition.
Unlike Spinosaurus aegyptiacus the original species described in 1915 from Egypt and often linked to coastal and delta environments S. mirabilis appears to have lived
farther inland. Both species show clear adaptations for eating fish and spending time in the water, but S. aegyptiacus is currently interpreted as being highly
specialized for semi-aquatic life, possibly even more adapted for swimming. The discovery of S. mirabilis suggests that different species of Spinosaurus
may have occupied slightly different habitats within North Africa’s vast river systems.
If you'd like to learn more about this newly described dinosaur, read the full news article on Spinosaurus mirabilis here, which
includes images of it's head crest and a video.
Fast Facts about Spinosaurus aegyptiacus
- Name:
Spinosaurus aegypaticus (pronunciation: "SPINE-oh-SAW-rus") - The name means "Spine lizard of Egypt" - Taxonomy:
Dinosauria (Dinosaur) - Saurischia (Lizard Hipped) - Theropoda (Beast Footed) - Spinosauroidea aka Megalosauroidea (Superfamily) - Spinosauroidea (Family) - Spinosaurus (Genus) - S. aegyptiacus (species) - Age:
Spinosaurus lived during the Cenomanian and Albian ages, 94-110 million years ago. It became extinct about 30 million years before T. rex appeared. - Discovery:
In 1912, Richard Markgraf found a partial specimen in the Baharia Oasis of Egypt. He sent the fossils to Ernst Stromer in Germany, and in 1915 this dinosaur was named Spinosaurus (Stromer, 1915). - Distribution:
S. aegyptiacus is only found in Northern Africa. Fossil locations include Egypt, Morocco, Algeria, Tunisia, Libya, and even Kenya. Other spinosaurids are found globally in Brazil, Asia, Europe, and Australia. - Body Size:
Spinosaurus was the longest theropod at around 15 meters (49 feet) with a skull over 4 feet long. It was about 10 feet longer than T. rex and 7 feet longer than Carcharodontosaurus, though those dinosaurs were bulkier. - Diet:
Spinosaurus' teeth and jaws were designed primarily for eating fish. - Habitat / Swimming:
Some research suggests Spinosaurus likely stayed along riverbanks and floodplains, stalking fish rather than swimming in open water, and was not a fully aquatic predator. - Designed for the Water:
Unlike other theropods, Spinosaurus had several aquatic specializations (Ibrahim 2014, 2020): - Crocodile-like head with a long, slender snout and interlocking pointy teeth for grasping large fish.
- Pressure sensors in the snout to detect moving prey in the water, similar to crocodiles.
- Long, crocodile-like tail ideal for propulsion in water.
- Possible webbed back feet.
- Hind legs adapted more for paddling than walking.
- Robust front arms with rigid hands to support weight when walking on all fours.
- Nostrils positioned further up on the skull, allowing breathing while mostly submerged.
- Dense bones, like whales and other aquatic mammals, for improved buoyancy while swimming and diving.
Spinosaurus aegyptiacus fossils have been found in the following formations:
| Mid-Late Cretaceous Formations | Locations |
|---|---|
| Bahariya Formation | Egypt |
| Aoufous Formation (Kem Kem Beds) | Morocco |
| Tegana Formation (Kem Kem Beds) | Morocco |
| Chenini Formation | Tunisia |
| Cabao Formation | Libya |
| Turkana Grits Formation | Kenya |
| "Gara Samani" | Algeria |
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The Discovery and Fossil Record of Spinosaurus
1911: Stromer and Markgraf: The Spine Lizard of Egypt
The story of Spinosaurus aegyptiacus, the iconic sail-backed dinosaur, begins in 1911 when Ernst Stromer, a Bavarian paleontologist, led an expedition
to the little-explored deserts of Egypt in search of mammal fossils. Stromer teamed up with Richard Markgraf, an Austrian fossil collector based near
Cairo, whose local knowledge proved invaluable.
Although the expedition yielded few mammal fossils, it uncovered a treasure trove of Cretaceous dinosaurs in the Baharia Oasis, including several large
carnivorous species. By 1912, Stromer returned to Germany while Markgraf continued excavating on-site. Later that year, Markgraf discovered a partial
skeleton of an unusually shaped dinosaur, which he carefully shipped to Stromer for study (Smith et al., 2006).
In 1915, Stromer formally described the specimen, naming it Spinosaurus aegyptiacus, meaning the "Spine Lizard of Egypt." This discovery marked the
first identification of the world's only known semi-aquatic giant theropod, cementing its place as one of the most fascinating dinosaurs of the Cretaceous period.
1936 Spinosaurus Reconstruction: Early Interpretations of the Giant Sail-Backed Dinosaur
As more fragmentary Spinosaurus fossils were discovered and sent to Ernst Stromer, by 1936 he had enough material to create the first full reconstruction. This early model depicted Spinosaurus as a massive, lumbering bipedal carnivore with a striking sail on its back.
1944 Spinosaurus Fossils Destroyed: The Loss of Stromer's Original Specimens
Ernst Stromer's Spinosaurus fossils had been on display at the Bavarian State Collection in Munich. During World War II, Stromer attempted to move
his specimens to safety, but in 1944 an Allied bombing raid destroyed the museum and obliterated all of Stromer's original Spinosaurus fossils.
For decades, this iconic Cretaceous predator remained largely a mystery. Only fragments of Spinosaurus and related spinosaurids were occasionally
discovered, but nothing substantial enough existed to allow a complete analysis or accurate reconstruction. As a result, Spinosaurus remained enigmatic for over 50 years.
2008-2020: Nizar Ibrahim's New Spinosaurus Discoveries and Semi-Aquatic Insights
In 2008, paleontologist Nizar Ibrahim was conducting fieldwork in the Cretaceous Kem Kem Beds near Erfoud, Morocco.
While there, he acquired a small box containing unusual dinosaur bones embedded in a distinctive purple matrix with yellow streaks. The fossils also
had a unique cross-section, setting them apart from typical finds.
A year later, at the Natural History Museum in Milan, Italy, Ibrahim was shown a partial dinosaur specimen from Morocco. He immediately recognized it
as a rare Spinosaurus specimen, similar in appearance to his 2008 fossils. Realizing the significance, he aimed to locate the original
dig site to recover more of the specimen.
Four years later, Ibrahim returned to Erfoud to track down the fossil dealer. After numerous false leads, he almost gave up-until, by chance, he
recognized the dealer walking by a cafe. The dealer guided him to the excavation site, where Ibrahim, alongside Paul Sereno, returned
with a team to uncover additional parts of the Spinosaurus specimen. Using digital measurements of their new fossils, Stromer's photographs,
and other fragmentary North African finds, they conducted a detailed analysis. In 2014, Ibrahim and colleagues published the most
accurate reconstruction of Spinosaurus to date, revealing it as a semi-aquatic dinosaur.
Following this publication, Ibrahim returned to Morocco and excavated an area adjacent to the original specimen. In 2018, his team unearthed an 80% complete
tail of a juvenile Spinosaurus-previously missing from all specimens. The discovery revealed a paddle-shaped tail, similar to a crocodile, ideally suited for water propulsion,
providing strong evidence that Spinosaurus was aquatic. These groundbreaking findings were published in a 2020 paper, confirming the unique semi-aquatic
adaptations of this remarkable Cretaceous predator.
Aquatic Adaptations of Spinosaurus: Skull, Limbs, Tail, and Bone Density
Members of the Spinosauroid family show some aquatic adaptations, but Spinosaurus aegyptiacus took these features to an extreme. Its skull, teeth, limbs, tail, and even bone density were specialized for a semi-aquatic lifestyle. Overall, Spinosaurus resembled a crocodile or an early cetacean (whale) more than a typical theropod. Below are the key aquatic adaptations of this remarkable dinosaur.
YOUTUBE VIDEO - Spinosaurus Aquatic Adaptations
5 minute Video about Spinosaurus from Nature with Nizar Ibrahim's new findings from his 2020 paper.
The Teeth: Ideal for Grasping Fish
Unlike other theropods, Spinosaurus teeth were long, conical, and peg-like rather than blade-like and serrated. Stromer noted they were unlike any other theropod teeth. These peg-like teeth are perfect for grasping fish and slippery aquatic prey, similar to crocodiles, toothed whales, and even sand tiger sharks. The teeth were not designed for slicing large chunks of meat or crushing bones.
The Skull: Crocodile-Like Adaptations
Spinosaurus' narrow jaws resemble the Gavial, a fish-eating crocodile, and are optimized for catching smaller aquatic prey rather than tackling large,
struggling animals. The front of the snout contains numerous small foramina, which, according to Ibrahim et al. (2014), function as pressure sensors to
detect movement in water.
The nostrils are positioned further back on the skull, allowing Spinosaurus to breathe while mostly submerged, similar to early whales. Unlike crocodiles,
Spinosaurus lacked large muscle attachment areas for powerful bite forces, emphasizing its specialization for fish and aquatic prey.
Limbs and Tail: Swimming Specialists
The Tail: Designed for Water Propulsion
Spinosaurus had an unusually long, flexible tail with tall processes, unlike the rigid tails of most theropods. This paddle-shaped tail was ideal for
lateral bending, enabling propulsion through water, much like crocodiles and bony fish (Ibrahim et al., 2020).
The Hind Limbs: Adapted for Swimming
The pelvis and hind limbs were shortened but robust, with strong muscle attachments, similar to semi-aquatic mammals and early whales (Ibrahim et al., 2014).
The hind feet were flattened and possibly webbed, adapted for walking on soft substrates or paddling in water.
The Hind Limbs: Adapted for Swimming
The pelvis and hind limbs were shortened but robust, with strong muscle attachments, similar to semi-aquatic mammals and early whales (Ibrahim et al., 2014).
The hind feet were flattened and possibly webbed, adapted for walking on soft substrates or paddling in water.
Spinosaurus' center of gravity was shifted toward its rib cage, making bipedal locomotion difficult. Forelimbs were necessary for support, indicating Spinosaurus
was likely quadrupedal on land, further emphasizing its aquatic adaptations (Ibrahim, et al. 2014 and 2020).
Dense Bones: Like Early Cetaceans (Whales)
Spinosaurus had exceptionally dense bones - 30-40% denser than other theropods - which improved buoyancy control for swimming and diving (Ibrahim et al., 2014). This high bone density is similar to early whales, highlighting Spinosaurus' evolutionary adaptations to an aquatic environment.
This cast is on display at the Smithsonian Museum of Natural History in Washington, D.C.
The Sail of Spinosaurus
Spinosaurus' dorsal vertebrae had massive processes, over 5 feet tall, forming the tallest known vertebral spines of any dinosaur. Stromer originally proposed they formed a sail. Later studies suggested a hump or thermoregulatory function, but Ibrahim et al. (2014) found the spines were dense, non-vascularized, and had ligament scars along the edges, confirming the sail likely served as a display structure, possibly visible while swimming.
Conclusion and 3D Model
The rediscovery and analysis of Spinosaurus show it was at least semi-aquatic. Its crocodile-like skull and peg teeth, posteriorly positioned nostrils,
dense bones, paddle-like tail, and wide, flat hind feet make it one of the most specialized aquatic theropods known.
The story does not end here. Paleontologists, including Henderson (2018) and Hone & Holtz (2021), suggest that Spinosaurus was not fully aquatic.
Henderson's simulations of buoyancy, based on bone density and lung placement, indicated that it could not dive and would have been unstable at the
water's surface, with its sail causing it to roll to one side. Hone and Holtz also proposed that it likely stayed along riverbanks, stalking fish rather than swimming in open water. The discovery
of a second Spinosaurus species, Spinosaurus mirabilis, in 2026 in
inland Cretaceous deposits of central Niger, far from the coast, further supports the idea that spinosaurids inhabited rivers and floodplains rather than
being fully open-water swimmers.
Below is an interactive 3D model of Spinosaurus that uses the new findings including the paddle-like tail that is clearly designed for water propulsion.
3D INTERACTIVE MODEL - Spinosaurus with Texture - Tap to Start Model
Interactive 3D Model of Spinosaurus by Julian Johnson-Mortimer (CC BY 4.0) on Sketchfab
