Palaeontologists have revealed an extraordinary new species of dinosaur. This giant theropod, named Spinosaurus mirabilis, lived around ninety-five million years ago in what is now the central Sahara Desert. It is the first new species in the Spinosaurus genus described in more than a century.

The discovery challenges long-held ideas about how spinosaurids lived and hunted. The name mirabilis means “marvellous” in Latin, reflecting the unique and striking anatomy of this Cretaceous piscivore.

A Spinosaurus mirabilis has caught a coelacanth. Picture credit: D. Navarro.

Picture credit: D. Navarro

A Remarkable Discovery

The story began in 2019 when scientists pulled a massive, oddly shaped bone from Sahara sands. The scimitar-shaped crest of this dinosaur was so large and unexpected that the scientists initially did not recognise it for what it was. Only after a return expedition was despatched (2022) and the discovery of additional fossils did the truth emerge — a new dinosaur species had been found.

The research team, led by the University of Chicago’s Paul Sereno, published the findings in the academic journal “Science”.

Based on the crest’s surface texture and interior vascular canals, the study team concluded that this crest was sheathed in keratin.  It may have been brightly coloured and played a role in species identification and visual display.

Ana Lázaro holding crest of Spinosaurus mirabilis in field. Picture credit: Alvaro Simarro.

Picture credit: Alvaro Simarro

Another striking feature of the skull is its interdigitating upper and lower tooth rows. These make a deadly trap for slippery fish. Interdigitating teeth, where those of the lower jaw protrude outward and between those of the uppers, is a time-honoured adaptation on among piscivores in the fossil record. For example, this type of dentition is found in ichthyosaurs, crocodilians and pterosaurs. Among dinosaurs, it sets Spinosaurus and closest kin apart.

Commenting on the significance of this discovery, lead author Paul Sereno, (PhD, Professor of Organismal Biology and Anatomy at the University of Chicago) stated:

“This find was so sudden and amazing, it was really emotional for our team. I’ll forever cherish the moment in camp when we crowded around a laptop to look at the new species for the first time, after one member of our team generated 3D digital models of the bones we found to assemble the skull — on solar power in the middle of the Sahara. That’s when the significance of the discovery really registered.”

Field team members getting their first look at the tall crested Spinosaurus skull. Picture credit: Jessica Schwartz.

Picture credit: Jessica Schwartz

What Made Spinosaurus mirabilis Special?

Previously, spinosaurid bones and teeth had only been found principally in coastal deposits. This led to some experts postulating that these fish-eating theropods may have been fully aquatic, pursuing prey underwater. However, the new fossil area in Niger documents animals that were living inland, some 500 to 1000 km from the nearest coastline. The proximity of the spinosaurid material to the fossilised remains of sauropods suggest that this was a forested, inland ecosystem crossed by many rivers.

Paul Sereno added:

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

Paul Sereno with a cast of the skull of Spinosaurus mirabilis. Picture credit: K. Ladzinski.

Picture credit: K. Ladzinski

An Amazing Journey

The journey that culminated in this remarkable fossil discovery began with a single sentence in a monograph from the 1950s.  A French geologist mentioned finding a single fossil tooth resembling those of the giant carnivore Carcharodontosaurus found in Egypt’s Western Desert at the turn of the last century.

The field team ended up meeting a local Tuareg man who led them on his motorbike deep into centre of the Sahara, where he had seen huge fossil bones. After nearly a day of travel with no shortage of doubts regarding the success of this venture, the local man led them to the fossil site (Jenguebi).  There, with little time to spare before returning to camp, the team found teeth and jaw bones of what turned out to be a new Spinosaurus species.

The snout end of Spinosaurus mirabilis weathering out of the substrate. Picture credit: Daniel Vidal.

Picture credit: Daniel Vidal

What Does this Mean for the Spinosauridae?

The discovery of Spinosaurus mirabilis expands our view of spinosaurid evolution. It shows that these theropods were not restricted to coastal habitats. Instead, they thrived inland inhabiting river systems.  This new Spinosaurus species suggests that the spinosaurids diversified in ways we are only beginning to understand.

This species helps fill a gap in the fossil record. It hints at a broader evolutionary story across Africa’s Cretaceous landscapes.

The locality, representing the Farak Formation may yield numerous vertebrate remains. The spinosaurid material is approximately ninety-five million old (Cenomanian faunal stage of the Late Cretaceous). At the end of the Cenomanian faunal stage, an abrupt rise in sea levels and climate change probably brought the spinosaurid radiation to an end.

The Phylogeny of Spinosaurus mirabilis

A time-calibrated phylogenetic analysis resolves three Spinosauridae evolutionary phases. Firstly, an initial Jurassic radiation when their distinctive elongate fish-snaring skull evolved and split into two distinctive designs, baryonychine and spinosaurine. Secondly, an Early Cretaceous circum-Tethyan diversification when both reigned as dominant predators. Finally, an early Late Cretaceous phase when spinosaurines attained maximum body size as shallow water ambush specialists limited geographically to northern Africa and South America.

The discovery of the tall-crested Spinosaurus mirabilis in a river system within an inland basin supports a lifestyle interpretation of a wading, shoreline predator with visual display an important aspect of its biology.

Everything Dinosaur acknowledges the assistance of a media release from the University of Chicago in the compilation of this article.

The scientific paper: “Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation” by Paul C. Sereno, Daniel Vidal, Nathan P. Myhrvold, Evan Johnson-Ransom, María Ciudad Real, Stephanie L. Baumgart, Noelia Sánchez Fontela, Todd L. Green, Evan T. Saitta, Boubé Adamou, Lauren L. Bop, Tyler M. Keillor, Erin C. Fitzgerald, Didier B. Dutheil, Robert A. S. Laroche, Alexandre V. Demers-Potvin, Álvaro Simarro, Francesc Gascó-Lluna, Ana Lázaro, Arturo Gamonal, Charles V. Beightol, Vincent Reneleau, Rachel Vautrin, Filippo Bertozzo, Alejandro Granados, Grace Kinney-Broderick, Jordan C. Mallon, Rafael M. Lindoso and Jahandar Ramezani. Paper published in the journal Science.

The award-winning Everything Dinosaur website: Museum Quality Dinosaur Models.

A remarkable Edmontosaurus skull fossil on display at the Montana State University’s Museum of the Rockies sheds new light on how members of the genus Tyrannosaurus tackled their prey. Moreover, this intriguing specimen forms the centrepiece of a new collaborative study involving scientists from Montana State University and the University of Alberta.  The research, published in the academic journal PeerJ, provides potential evidence of tyrannosaur hunting strategy as well as insights into feeding behaviour.

In 2005, a nearly complete Edmontosaurus skull (MOR 1627) was found in the Hell Creek Formation of eastern Montana on lands managed by the Bureau of Land Management. Importantly, the skull preserves a dramatic detail. A broken tyrannosaur tooth remains embedded in the dinosaur’s face. A partial tooth crown is embedded in the nasal bone. Consequently, it attracted the attention of doctoral researcher Taia Wyenberg-Henzler (University of Alberta) and Dr John Scannella, Curator of Palaeontology at the Museum of the Rockies.

The researchers wanted to identify the owner of the tooth.  Is this evidence of Tyrannosaurus rex hunting behaviour?

Rare Evidence of Ancient Behaviour

Although bite marks frequently appear on fossil bones, embedded teeth are extremely uncommon. Therefore, this specimen offers exceptional scientific value.

Co-author of the study, Wyenberg-Henzler explained:

“The great thing about an embedded tooth, particularly in a skull, is it gives you the identity of not only who was bitten but also who did the biting. This allowed us to paint a picture of what happened to this Edmontosaurus, kind of like Cretaceous crime scene investigators.”

Confirming the Culprit

Crocodilians or pterosaurs were quickly ruled out.  They compared the tooth crown with teeth from Hell Creek Formation theropods. The morphology most closely matched teeth from a large-bodied predator. Curvature and ovoid cross-sectional shape of the tooth further suggests that the tooth is a maxillary tooth from a middle or posterior tooth position. The researchers concluded that the embedded crown is most likely an adult Tyrannosaurus maxillary tooth rather than an immature Tyrannosaurus or Nanotyrannus tooth. Denticle shape also suggests that the embedded tooth is a tyrannosaurid tooth.

To read Everything Dinosaur’s recent blog post about evidence for Nanotyrannus being a valid taxon: Nanotyrannus Hyoid Bone Makes Crucial Breakthrough.

Furthermore, CT scans of the skull provided additional detail. These scans were carried out at Advanced Medical Imaging at Bozeman Health Deaconess Hospital. Dr Scannella (Museum of the Rockies) emphasised the importance of the find. The fossil captures a moment of behaviour, specifically a tyrannosaur biting into the face of a duck-billed dinosaur.

An artist’s reconstruction of the tyrannosaur attack on the unfortunate Edmontosaurus. Picture credit: Jenn Hall.

Picture credit: Jenn Hall

Predator or Scavenger?

Interestingly, the skull shows no signs of healing around the embedded tooth. The lack of reactive bone in the region surrounding the tooth suggests the animal died around the time the tooth became embedded in the nasal. Therefore, two possibilities remain. The Edmontosaurus may already have been dead when bitten. Alternatively, the attack itself may have been fatal.

Nevertheless, the position of the tooth offers further clues. The researchers noted that the impact angle suggests a face-to-face encounter. Typically, such injuries occur during active predation rather than casual scavenging. An examination of the hunting strategies of extant mammalian and reptilian carnivores confirmed that bites to the head are often employed to swiftly despatch prey.

The study authors conclude that the embedded tooth is most consistent with a bite inflicted during an attempt to control the struggling Edmontosaurus or deliver a killing blow followed by carcass consumption. In addition, the force required to snap a tyrannosaur tooth inside bone indicates a powerful, potentially lethal bite. Consequently, the evidence paints a vivid picture of the duck-billed dinosaur’s final moments.

Edmontosaurus Skull Provides New Insights into Tyrannosaurus Feeding Behaviour

The feeding ecology of Tyrannosaurus has long generated debate among palaeontologists. Some researchers have argued for active predation, while others have emphasised scavenging. However, this remarkable Hell Creek fossil adds an important data point. It provides rare, direct evidence of tyrannosaur feeding behaviour preserved in the fossil record.

For scientists and dinosaur enthusiasts alike, the specimen offers a compelling glimpse into the harsh realities of Late Cretaceous ecosystems.

Everything Dinosaur acknowledges the assistance of a media release from the Museum of the Rockies in the compilation of this article.

The scientific paper: “Behavioral implications of an embedded tyrannosaurid tooth and associated tooth marks on an articulated skull of Edmontosaurus from the Hell Creek Formation, Montana” by Taia C.A. Wyenberg-Henzler​ and John B. Scannella published in PeerJ.

The award-winning Everything Dinosaur website: Tyrannosaurus Models and Dinosaur Figures.