Spinosaurus mirabilis

Spinosaurus mirabilis is a recently described species of spinosaurid theropod dinosaur from fossil material found in the central Sahara, in the Jenguebi region of Niger, within early-to-middle Cenomanian river sediments, approximately 95 million years old. The species was formally established in a study led by Paul Sereno and colleagues, published in the journal Science in 2016, making it the first valid new species of the genus Spinosaurus described in over a century.

This spinosaurid was a large predator specialized in inland river environments. Current estimates place its body length at approximately 12 to 13 meters, with a potential mass of between 5 and 7 tons in adult individuals. Although it shares general traits with other spinosaurids, such as an elongated and narrow skull with a morphology similar to that of crocodilians, S. mirabilis has several diagnostic characteristics that clearly distinguish it from Spinosaurus aegyptiacus .

The most distinctive anatomical feature of this species is a massive scimitar-shaped cranial crest that rises above the nasal and prefrontal regions of the skull. This bony structure could reach approximately 50 cm in height, not including the keratinous sheath that likely covered it in life. Tomographic analysis of the bone tissue reveals a dense network of vascular canals, indicating that the crest was covered by a keratinous sheath, possibly brightly colored, and used in social display behaviors or intraspecific recognition. It is one of the largest known cranial ornamental structures among theropod dinosaurs.

The skull retains the typical spinosaurid morphology adapted to piscivory: an elongated and relatively narrow snout, posteriorly displaced nostrils, and dentition composed of conical, slightly recurved teeth lacking serrations, designed to capture slippery prey such as large fish. The anterior teeth exhibit an interdigitating pattern that functions as an effective trap for holding aquatic prey.

At the postcranial level, the animal also possessed a dorsal sail formed by elongated neural spines on the dorsal vertebrae, a typical feature of the Spinosaurinae clade. However, the functional interpretation of the animal differs somewhat from that proposed for S. aegyptiacus . The location of the fossil site—more than 500 to 1000 km from the Cretaceous coastline—indicates that this taxon inhabited forested continental riverine ecosystems with large rivers and abundant fish fauna. In this context, S. mirabilis would have acted primarily as a wading predator, ecologically comparable to a great egret, capable of venturing into waters up to approximately two meters deep to capture fish.

This interpretation suggests that, unlike the highly aquatic model proposed for other spinosaurids, Spinosaurus mirabilis was better adapted to walking in shallow water than to actively swimming for extended periods. Its body proportions and robust hind limbs appear consistent with a riparian predator lifestyle, specializing in stalking prey in inland river environments.

The discovery of this species provides important information about the late diversification of spinosaurids in Africa during the mid-Cretaceous and demonstrates that the genus Spinosaurus included ecologically distinct forms. Furthermore, it significantly expands our understanding of the evolution of piscivorous adaptations in theropods, suggesting a more complex ecological radiation within Spinosaurinae than previously proposed.

Approximate measurements of the Spinosaurus:

• 1:60 Scale Assembly Kit
  • Length 163 mm
  • Height 67 mm
  • Width 52 mm
  • Snout-tail length 210 mm
    
    
• 1:35 Scale Assembly Kit
  • Length 279 mm
  • Height 115 mm
  • Width 91 mm
  • Snout-tail length 360 mm