This skeletal reconstruction of Spinosaurus shows bones from the Egyptian discoveries by Stromer (orange), the new Moroccan finds (red and yellow), and bones modeled after other spinosaurid species (green and blue). | Tyler Keillor, Lauren Conroy, and Erin Fitzgerald/ Science/AAAS
Spinosaurus aegyptiacus — a flesh-eating dinosaur, significantly larger than Tyrannosaurus rex — was a fantastic swimmer in its day, new research shows. Until now, scientists had assumed that the ferocious carnivore was, like all other known dinosaurs, a land-dweller. But new fossils from Morocco suggest that S. aegyptiacus actually spent much of its time in the water.
The dinosaur has always been considered enigmatic, especially since the first set of S. aegyptiacus fossils was destroyed by a British bombing raid during World War II. At the time, the fossils only hinted at the creature's appearance, showing that it sported enormous backbones and an elongated skull. The researchers named it Spinosaurus, or "spine reptile."
Now, Nizar Ibrahim from the University of Chicago and colleagues from around the world present a much more complete set of S. aegyptiacus fossils that show specific adaptations for a semi-aquatic lifestyle. Their findings are published in the 12 September issue of Science.
Ibrahim and his colleagues expand upon the work of German paleontologist Ernst Stromer von Reichenbach, an outspoken critic of Nazi dictatorship who lost much of his family in addition to the first S. aegyptiacus fossils during the Second World War.
Nizar Ibrahim and David Martill examine a spine fragment of Spinosaurus found in southeastern Morocco | Cristiano Dal Sasso
"We had to wait close to 100 years for a new skeleton," explained Ibrahim during a 10 September press teleconference. "Our new Spinosaurus, from the Kem Kem region in southeastern Morocco, overlaps with Stromer's bones from Egypt. His drawings and publications survive, and they allowed us to make detailed comparisons. But the new find also preserves important parts of the skeleton that were not represented in the first skeleton."
The researchers' report describes the new fossils, which include portions of a skull, spinal column, pelvic girdle and limbs. Equipped with these new puzzle pieces, Ibrahim and his team created a digital model of an adult S. aegyptiacus, which suggests that the dinosaur was more than 49 feet (15 meters) long, or about as long as a tractor trailer.
Their analysis revealed that S. aegyptiacus spent much of its time in the water, feeding on sharks, sawfish and lungfish, and walked on all four limbs when it was on land.
"I think that we have to face the fact that the Jurassic Park folks have to go back to the drawing board on Spinosaurus," said Paul Sereno, a co-author of the Science report from the University of Chicago. "It was not a balancing, two-legged animal on land. It would have been something very peculiar."
The dinosaur could probably retract its fleshy nostrils to a spot on top of its head and use its flat feet to propel itself through water, according to the researchers. The pelvic girdle and hind legs of S. aegyptiacus were smaller than those of related species, and the dinosaur's center of gravity appears to have been shifted to the rear in order to facilitate swimming, they say.
Paul Sereno describes some of Spinosaurus's unusual skeletal traits. | University of Chicago
The researchers also suggest that the creature's neck, spine and tail were adapted for pursuing prey underwater — and that the "sail" on its back probably remained visible as a fin when S. aegyptiacus was in the water.
"The place Spinosaurus lived was a bizarre ecosystem," Ibrahim explained. "It was a fairly diverse river system with things like temporary lakes, deltas and some very large and wide rivers. The river system was home to many large aquatic vertebrates — and when I say 'large,' we're talking about giant, car-sized, seven-meter sawfish, giant lungfish, several different kinds of sharks, and six to eight different kinds of crocodile-like predators."
The researchers are quick to acknowledge all of the great detective work on the species that was performed before their time."Stromer's papers were beautifully illustrated, and it was his detailed work on these papers that allowed us to go as far as we did," said Sereno.
"My hope is that this great discovery and its incredible background story will encourage decision-makers in my country to do more to protect our incredible paleontological and geological heritage," said Samir Zouhri, a study co-author from Université Hassan II in Casablanca, Morocco.