Paleontologist Who Uncovered Prehistoric River Monster's Tail Explains Why It's Such a Game-Changer

Three years after the glittering Crystal Palace drew luminaries like Charles Darwin, Karl Marx, Charles Dickens, Charlotte Brontë and Lewis Carroll to a world's fair exhibition in London, the cast-iron and plate-glass building—a technological marvel for the time—reopened miles to the south, in the town of Bromley, with a new exhibition that made almost as big a splash: dinosaurs. Employing 1854's most up-to-date paleontological science, sculptor Benjamin Waterhouse Hawkins created statues in 15 genera of extinct animals, including dinosaurs like the ankylosaurian Hylaeosaurus, Jurassic-period predator Megalosaurus and the herbivorous Iguanodon.

Workers cleaning one of the Crystal Palace dinosaurs in 1927. Photo by Fox Photos/Getty Images

Squatting, lizard-like and arrayed in or near bodies of water, the cutting edge depictions were quickly made obsolete by an explosion of new discoveries. The park's dinosaurs—still standing today—became avatars of the outdated, and discoveries since have consistently brought paleontology further away, toward more aerobic, warmblooded, active—even feathered—dinosaurs. Meanwhile, massive aquatic, non-dinosaur reptile discoveries populated the Mesozoic oceans with bus-sized predators like the Mosasaurus (seen chomping people and dinosaurs alike in the Jurassic World movies).

So when paleontologist and National Geographic Explorer Nizar Ibrahim, assistant professor of biology at University of Detroit Mercy, began proposing that the largest dinosaur predator ever discovered—Spinosaurus—may have lived a primarily aquatic lifestyle, the paleontological community was hesitant to agree. While adaptations like conical teeth for eating fish and flat-bottomed feet for paddling suggested a semi-aquatic lifestyle, with the spinosaurus hunting in and along waterways, there wasn't yet justification to rethink dinosaurs as fully occupying aquatic ecosystems as completely as on land.

But Ibrahim and his colleagues' theories regarding aquatic dinosaurs were confirmed in spectacular fashion on Wednesday, when National Geographic unveiled the discovery of a mostly intact Spinosaurus tail completely unlike anything found on a dinosaur before (for more on this discovery visit

In their paper "Tail-propelled aquatic locomotion in a theropod dinosaur," published Wednesday in the academic journal Nature, Ibrahim and an international team presented "unambiguous evidence for an aquatic propulsive structure in a dinosaur." Their Spinosaurus had long spines emerging from its tail vertebrae, forming a flat paddle for propelling it through the water.

Cristiano Dal Sasso, Italian Paleontologist (Milan Museum of Natural History), part of the Italian team of the Spinosaurus expedition. Cristiano is holding one of the first—and most complete—caudal vertebrae (tail bones): Caudal 4. The caudal series of Spinosaurus aegyptiacus was found in the Kem Kem region of Morocco. The vast majority of the tail bones were found in 2018 and 2019. Paolo Verzone/National Geographic

"This could have been a real, long-term invasion of aquatic habitats by dinosaurs, which is something that up to this point was kind of unthinkable," Ibrahim told Newsweek. "I think the main reason why people were reluctant to accept Spinosaurus as a fully aquatic animal is that up until now we didn't really have the propulsive structure, the motor, that would propel these animals through the water. Now we have it."

This Spinosaurus lived more than 90 million years ago, in a lowland delta of ponds, lakes and rivers that stretched from modern-day Morocco to Egypt—an area approximately the size of the continental United States. Ibrahim referred to it as "the river of giants," because of the colossal animals the sprawling ecosystem supported, including car-sized coelacanth, lungfish and sawfish with eight-foot snouts and barbed teeth.

"That's one of the really interesting things about the Sahara a 100 million years ago: it supported a dizzying diversity of massive animals," Ibrahim said. "Not just dinosaurs, but big crocs and fish and flying reptiles. Spinosaurus—being a river monster, essentially—preyed primarily on the abundant fish in the ecosystem."

Spinosaurus was a formidable predator in this environment: 50 feet long, 16,000 pounds, with a skull nearly as long as a person is tall. Spinosaurus also sported a neural spine sail, which Ibrahim and eight co-authors suggested in 2014 may have functioned as a display that could be seen above water—like a shark fin six feet tall. But with the discovery of Spinosaurus' fin-like tail, that dorsal sail may have played a more active secondary function, providing stability, like a keel. Spinosaurus would have competed for prey with giant crocodilian animals like the Elosuchus in the water, and shared its broader ecosystem with pterosaurs overhead and Carcharodontosaurus the size of T. rex hunting the land with steak-knife teeth.

A (now outdated) Spinosaurus model on display outside the Museum of Natural Sciences in Barcelona on July 12, 2016. JOSEP LAGO/AFP via Getty Images

"One of the reasons Spinosaurus is, for me, kind of the Holy Grail of dinosaur paleontology is because it was so elusive," Ibrahim said. "There was only one skeleton, found decades ago. It was destroyed in World War II."

That specimen, discovered in Egypt in 1915, was lost when more than 900 Allied bombers attacked Munich in April 1944. Since then, Spinosaurus vertebrae, teeth and snout bones have been uncovered in the desert-bound geological Kem Kem beds, where an expedition lead by Ibrahim; paleontologist Samir Zouhri, of the Université Hassan II in Casablanca; and paleontologist David Martill of the University of Portsmouth uncovered additional Spinosaurus bones in 2013.

The find in Morocco was enough to write up a new description of Spinosaurus, but it wasn't until a 2018 return expedition supported by a grant from the National Geographic Society that the team uncovered more than 30 Spinosaurus vertebrae, including from the previously mysterious tail, which had been presumed similar to other theropod predators in previous models. Instead, the tail vertebrae had two-foot bones, thin enough to support a tall, thin tail, like a flat paddle.

"This is not like going fossil hunting in Montana or Wyoming or some places in Canada where you find almost complete dinosaur skeletons just weathering out of the ground," Ibrahim said, describing both geologic and practical obstacles to leading a team into the hostile Sahara desert.

Team members (from the left from top to down): Ayoub Amane, student, Hassan II University of Casablanca, Geology Department, Casablanca; Samir Zouhri, professor of Paleontology, Hassan II University of Casablanca, Geology Department; Cristiano Dal Sasso, Italian Paleontologist at the Milan museum of natural history; Gabriele Bindellini, Paleontologist, PhD Student and photogrammetry expert at the University of Milan, (in the center of the picture); Marco Auditore, Italian scientific illustrator; Simone Maganuco, independent researcher and Paleontologist; M’Barek Fouadassi, Moroccan team member, and Nizar Ibrahim, PhD, Paleontologist, National Geographic Explorer, Assistant Prof of Biology at the University of Detroit Mercy, excavating a Spinosaurus bone. Paolo Verzone/National Geographic

"A lot of blood and sweat went into making this discovery. Everything that could possibly go wrong did go wrong," Ibrahim said. "We had sandstorms, we had torrential flooding (in the desert, mind you), we lost one of our field vehicles. We had all kinds of equipment fail us, like a jackhammer we used to remove over 15 tons of rock in 120 fahrenheit. The list goes on and on. You can see why people might go, you know what, I'll just stick with Montana."

But the results are spectacular: the most complete Cretaceous period predatory dinosaur ever found in Africa, with around 60 percent of the animal unearthed, including fragments of the skull and most of the Spinosaurus' unexpected tail.

In 2001's Jurassic Park 3, Spinosaurus appears as a bigger, nastier replacement for Tyrannosaurus, snapping a T. rex's neck, then chasing paleontologist Alan Grant—who can speak to Velociraptors now—across land and water. Similar to other predatory theropods across the 140 or so million years spanning the Jurassic and Cretaceous, the movie's Spinosaurus walked upright, balanced by a long and stiff tail.

But now, with the discovery of Spinosaurus' tail, we are confronted with a very different animal, with a posture more suited for swimming than running on land. It may have been more accurate to have pitted Sam Neill and William H. Macy against a titanic newt.

"When you're dealing with an animal like Spinosaurus there's no blueprint you can look at," Ibrahim said.

So the discoverers of the Spinosaurus tail started searching the scientific literature ("and Google," Ibrahim admitted) for useful comparative anatomies. They found a surprisingly similar silhouette—albeit only 1/100 the length—in the Danube crested newt, with its jagged dorsal crest and oar-shaped tail, which it uses to pursue tadpoles across Hungarian riverbeds. The newt was selected as one of four species used in comparative tail swimming measurements, which compared laser-cut models of tails, mounted underwater on a robotic drive shaft.

"We confirmed that the Spinosaurus tail would generate substantial thrust," Stephanie Pierce, Associate Professor of Organismic and Evolutionary Biology at Harvard University, told Newsweek.

The efficiency of the 2D plastic Spinosaurus tail shape generated more thrust than the tails belonging to land-based carnivores Coelophysis and Allosaurus, but less than the Nile crocodile or crested newt. While Pierce emphasized that Spinosaurus swimming locomotion still had many unknowns—including whether or not it paddled with its limbs—the shape of the dinosaur's tail allowed for a leisurely underwater cruising speed over five miles per hour.

"Contrary to recent suggestions that Spinosaurus was confined to wading and the apprehension of prey from around the edges of bodies of water, the morphology and function of its tail—along with other adaptations for life in water—point to Spinosaurus having been an active and highly specialized aquatic predator that pursued and caught its prey in the water column," the team concluded in the Nature paper.

This finding was backed up by the loose interlock between the caudal—or tail—vertebrae, which would have given Spinosaurus more flexibility than the stiffer, balancing tails of land-bound dinosaur predators.

"We think that it is likely that with such a large and flexible tail, Spinosaurus had considerable maneuverability, and of course the ability to capture prey in different directions was enhanced by the long neck," George Lauder, Professor of Organismic and Evolutionary Biology at Harvard University, told Newsweek.

Paleontology involves detective work both in the field and the lab, so Ibrahim, Lauder and Pierce all emphasized that the Spinosaurus discovery doesn't just put to rest a debate over the lifestyle of the Cretaceous giant, but also introduces all new questions.

"The really exciting thing for me and my team—which by the way was the most amazing team you could imagine; I had extremely hardworking and sharp colleagues working with me on this paper—the reason why I was excited about this is unlike most other paleontology stories, it's not just a find that adds to an existing narrative," Ibrahim told Newsweek. "This discovery opens up a whole new world of ecological possibilities."

This reframing of dinosaurs as competitors in watery ecosystems will most likely begin with the Spinosaurus' ancestors—spinosaurids like the fish-eating Baryonyx and Suchomimus of the early Cretaceous—which may have lead more aquatic or semi-aquatic than previously believed, even without extreme adaptations like Spinosaurus' paddle tail. After decades of moving away from century-old dogma portraying dinosaurs as swamp-bound lizards, paleontologists can now reexamine the possibilities of aquatic dinosaurs with fresh eyes and new data.

"I think a lot of people will now go back to their museum collections and see that maybe other dinosaurs there were misinterpreted or overlooked in the past that may show similar adaptations," Ibrahim said. "And there are still countless paleontological treasures just waiting to be uncovered in different parts of the world, particularly in places like Africa, which has been neglected in many different ways. That's one of the things we're trying to change with our research. Spinosaurus is one part of this, but we're really trying to put African dinosaurs—and the animals that live alongside them—on the map."

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