New fossils rewrite the story of dinosaur evolution and ecology — and change the appearance of Spinosaurus

April 29, 2020
University of Detroit Mercy professor Nizar Ibrahim holds pickaxe at dig site with fellow explorer.

Scientists have long opposed the idea that dinosaurs lived in aquatic habitats. Now, an international team of researchers, led by National Geographic Explorer and University of Detroit Mercy professor Nizar Ibrahim, has discovered unambiguous evidence that Spinosaurus aegyptiacus, the longest predatory dinosaur known, was aquatic, and used tail-propelled swimming locomotion to hunt for prey in a massive river system. It is the first time that such an adaptation has been reported in a dinosaur.

The findings, published today in the journal Nature and featured on, are based on a multidisciplinary investigation of the world’s only existing Spinosaurus skeleton, found in the Kem Kem region of the Moroccan Sahara. The skeleton is now also the most complete one to date for a Cretaceous predatory dinosaur from mainland Africa.

“This discovery really opens our eyes to this whole new world of possibilities for dinosaurs,” Ibrahim said. “It doesn’t just add to an existing narrative, it starts a whole new narrative and drastically changes things in terms of what we know dinosaurs could actually do. There’s nothing like this animal in over 220 million years of dinosaur evolution, which is pretty remarkable.”

Led by Ibrahim, the team returned to the site where parts of a Spinosaurus skeleton had first been uncovered in 2008. In a previous study, Spinosaurus had been identified as a fish-eating dinosaur with adaptations for an amphibious lifestyle, supported by its relatively short hindlimbs, wide feet, dense bones and elongated jaws studded with conical teeth. However, suggestions that it may have been a truly water-dwelling dinosaur were met with considerable opposition, in large part because the partial skeleton provided little to no evidence of the propulsive structure needed to move such a giant dinosaur through water.

Between 2015 and 2019 Ibrahim’s team recovered many more fossils of the skeleton, including a remarkably complete, fin-like tail capable of extensive lateral movement and characterized by extremely long spines.

After preparing all of the fossils, the team used photogrammetry to digitally capture the anatomy of the tail.

To quantitatively assess the performance of the tail, a team of Harvard researchers made a flexible model of the tail and attached it to a robotic system that mimics swimming movements. They then compared the swimming performance of the Spinosaurus tail to model tails from other animals, including other dinosaurs, crocodiles, and newts. The results were fully consistent with the idea of a truly water-dwelling, tail-propelled, “river monster.”

“This discovery is the nail in the coffin for the idea that non-avian dinosaurs never invaded the aquatic realm,” Ibrahim said. “This dinosaur was actively pursuing prey in the water column, not just standing in shallow waters waiting for fish to swim by. It probably spent most of its life in the water.”

The discovery also points to the possibility of a persistent and widespread invasion of aquatic habitats by relatives of Spinosaurus.

“This new discovery changes our current understanding of dinosaurs and reflects Dr. Ibrahim’s boundless curiosity and dedication to uncovering the secrets of the Sahara’s dinosaurs," said Alex Moen, vice president of explorer programs at the National Geographic Society. "His work is at the nexus of science and exploration, and embodies the unique role National Geographic has in illuminating the wonder of our world.”

Today, all of the original bones found throughout the project are housed at the University of Casablanca in Morocco. For Professor Samir Zouhri, capacity and infrastructure building in North Africa was a major goal of this research project.

“In the past, Moroccan fossils like this one would inevitably end up in collections in Europe, Asia, or the United States,” he stated. “Now we have the best collection of Kem Kem fossils right here in Morocco, including the most complete predatory dinosaur from the Cretaceous of mainland Africa. This is a game changer.”

Media coverage

Most dinosaurs didn’t swim—but this ‘dino equivalent of Jaws’ sure did
Popular Science | 5/14/20
The ancient animals have been thought to be exclusively land-lovers, until now.

Swimming Dinosaurs: Paleontologists Unearth Spinosaurus Fossils
NPR | 5/7/20
Paleontologists in the Moroccan Sahara have unearthed one of the largest intact dinosaur fossils ever found in the region, and their discovery could be the first example of a dinosaur with an aquatic lifestyle.

A war, bones dealer and a desert expedition: The story behind learning Spinosaurus could swim
CNN | 4/29/20
Unlike most dinosaurs, it seems that Spinosaurus liked the water. This suggestion is based on the analysis of a well-preserved fossil tail of Spinosaurus aegyptiacus, published Wednesday in the journal Nature.

A Strange Dinosaur May Have Swum the Rivers of Africa
New York Times | 4/29/20
The Spinosaurus possessed a long, powerful tail. Paleontologists think the dinosaur used that to propel itself through water.

Team presents groundbreaking evidence Spinosaurus dinosaur was aquatic
ABC News | 4/29/20
The Spinosaurus is thought to have been a 50-foot predatory, water-loving beast.

Terrifying Spinosaurus had powerful tail, becoming first known dinosaur to live underwater
FOX News | 4/29/20
Researchers have discovered that Spinosaurus aegyptiacus, the terrifying aquatic dinosaur that lived 100 million years ago, had a powerful tail that enabled it to live underwater, making it the first known dinosaur to do so.

A swimming dinosaur: The tail of Spinosaurus
Nature | 4/29/20
A new fossil of one of the most unusual dinosaurs, Spinosaurus aegyptiacus, suggests it was a swimming predator powered by a fin-like tail. Paleontologist Nizar Ibrahim has been working at the dig site in the Sahara and describes his amazement at the unique tail bones they found under the rock and sand.

'River monster': Huge African dinosaur Spinosaurus thrived in the water
Reuters | 4/29/20
The huge African predator ​Spinosaurus spent much of its life in the water, propelled by a paddle-like tail while hunting large fish — a “river monster,” according to scientists.

Bizarre Spinosaurus makes history as first known swimming dinosaur
National Geographic | 4/29/20
A newfound fossil tail from this giant predator stretches our understanding of how—and where—dinosaurs lived.

Reconstructing a gigantic aquatic predator
National Geographic | 4/29/20
Explore how scientists discovered the largest predator ever lived and hunted almost entirely in the water.

New Spinosaurus fossil proves the villain of Jurassic Park III could indeed swim
SYFY | 4/29/20
Spinosaurus aegyptiacus, aka the dreaded, spine-backed antagonist from the 2001 film, is now considered to be the first dinosaur that was able to live underwater.

Hundred million-year-old 'river monster' with a powerful fin-like tail is discovered in the Sahara — proving that dinosaurs DID live underwater
Daily Mail (UK) | 4/29/20
The first ever evidence of a dinosaur which swam, lived and hunted underwater has been discovered in the now-barren wilderness of the Saharan desert.

Terrifying 50-FOOT ‘river monster’ with huge teeth for gobbling prey is first aquatic dinosaur
The Sun (UK) | 4/29/20
A terrifying "river monster" that measured up to 50-foot long once hunted prey across the Sahara Desert.

'River-monster' discovered that was a cross between T-Rex and Great White Shark
The Mirror (UK) | 4/29/20
Spinosaurus was a cross between T-Rex, a Great White Shark and a crocodile that had a paddle-like tail and a bony sail like structure on its back.

Scientists discover first ‘river monster' dinosaur
The Irish News | 4/29/20
Scientists have rewritten the textbooks with the discovery of the remains of the first “river monster” dinosaur.

Scientists pinpoint 'most dangerous place in the history of planet Earth'
CNET | 4/29/20
A paleontologist says time travelers would not survive long in this predator-packed area of Africa 100 million years ago.

Spinosaurus Natonal Geographic Discovery
FOX2 Detroit | 5/12/20
A new dinosaur discovery by a University of Detroit Mercy Professor changes what we know.

A Dangerous and Mysterious Prehistoric Predator
BYU Radio | 6/25/20
The 50-foot-long spinosaurus was one of the most terrifying prehistoric creatures, but it didn’t roam the earth like the T. rex—it was actually lurking underwater.

Infographic on recently discovered dinosaur by University of Detroit Mercy professor Nizar Ibrahim
University of Detroit Mercy professor Nizar Ibrahim holds recently discovered fossil.