The largest predatory dinosaur to walk this earth wasn’t the T. rex. It was Spinosaurus aegyptiacus, a 50-foot long creature with powerful jaws and a solid, spiny sail on its back that dwelled in Northern Africa 95 million years ago. But even though paleontologists have known about this particular dinosaur for almost a century, its true form has only just been revealed.

"The only dinosaur that shows [aquatic] adaptations."

This is "the first water-adapted non-avian dinosaur on record," said University of Chicago paleontologist Paul Sereno in a press conference yesterday. Sereno is part of a team of researchers that was finally able to reconstruct Spinosaurus in full using newly discovered fossils and information gathered from the dinosaur’s initial discoverer, a German paleontologist named Ernst Stromer. According to their reconstruction, published today in Science, Spinosaurus aegyptiacus was a gigantic fish-eating, water-paddling marvel; one that, in Sereno’s words, was "a chimera — half duck, half crocodile."

"Spinosaurus is the only dinosaur that shows [aquatic] adaptations," said Nizar Ibrahim, a study co-author and paleontologist also at the University of Chicago. These include "a nose opening far back on the skull" which allowed the animal to breathe when its head is partially submerged, he said, as well as cone shaped teeth and slender jaw that would have allowed it to catch aquatic prey. The dinosaur’s hip and leg bones were also reduced compared to other Spinosaurus species. "This is something we’ve seen animals that return to the sea such as the ancestors of modern whales," Ibrahim said.

"it is going to force dinosaur experts to rethink many things they thought they knew about dinosaurs."

Moreover, its bones were very dense and compact — an adaptation that the researchers think was meant to help it with buoyancy control in water. "The animal we are resurrecting is so bizarre," Ibrahim said, that "it is going to force dinosaur experts to rethink many things they thought they knew about dinosaurs."

Yet, despite Ibrahim's claim, Spinosaurus’ oddly shaped body isn’t the only surprising aspect of the discovery. Arguably, the events that allowed the researchers to come to these conclusions are just as captivating.

Credit: Tyler Keillor, Lauren Conroy, and Erin Fitzgerald, Ibrahim et al., Science/AAAS

"Spinosaurus were first named by German paleontologist, Ernst Stromer" in 1915, Ibrahim explained. Back then, Stromer described several bizarre backbones with spines — "some as tall as a person," Ibrahim said, and slender jawbones. Based on that finding alone, Stromer was able to deduce that he was likely dealing with a fish-eating dinosaur that was larger than the 40-foot long North American Tyrannosaurus rex. He didn’t possess enough information to guess at its aquatic lifestyle, however. And sadly, the bones he collected were lost in 1944, when a Royal Air Force raid destroyed the Bavarian State bone collection in Munich.

Although some of Stromer’s descriptions and drawings were recovered, Ibrahim said, "Spinosaurus was seemingly lost forever."

"Spinosaurus was seemingly lost forever."

Yet, by chance, Ibrahim met an amateur fossil collector in Morocco in April 2008 while conducting research for his PhD. "He had a cardboard box and inside were several bones," he said. "They were mostly covered in sediment [...], but one bone really caught my attention." It wasn’t until much later that the researcher found out what is was: the spine of a Spinosaurus.

"We made sure that [the bones] were deposited in the university collection at Casablanca where all our finds are curated," he said, "and I thought maybe one day I’ll figure out what these bones are." Eventually, Ibrahim’s Italian colleagues, Cristiano Dal Sasso and Simone Magsanuco, told him the truth. "But we had one big problem; my Italian colleagues didn’t know where exactly the skeleton came from, you know?" And so, Ibrahim and his colleagues set out to track down the amateur fossil hunter that had given them the spine. Ibrahim knew nothing about him, except that he sported a mustache.

Still in 2013, they found him. "We were just sitting at a café in Erfoud sipping mint tea and I just saw all of my dreams going down the drain," Ibrahim said. And in that very moment, the researcher spotted him, the mustachioed man, walking past his table in the café. "I just caught the glimpse of his face, but I immediately recognized it."

"We found 'our needle in the Sahara.'"

The man remembered Ibrahim, and agreed to take the researchers to the site in Morocco where he had found the spine. There, the paleontologists found vertebrae, teeth, and jaw pieces belonging to Spinosaurus. "We found our 'needle in the Sahara.' And so that’s when we started the real scientific work."

Over the course of the next year, the researchers worked tirelessly to compile information from Stromer’s sketches, records from various other museums, and the fossils they collected in Morocco, in a single 3D model of the gigantic, semi-aquatic Spinosaurus. "We didn’t overturn a single thing [Stromer] said — an astounding fact considering that he just had the material that he collected from the early part of the century," Sereno said. "It’s really a tribute to [Stromer’s] excellent work and, in fact, his excellent interpretations."

Now that the researchers have the skeleton in place, they hope to use the 3D models they generated to study how it might have moved on land, as well as in water. Chances are that it wasn’t all that graceful on land, Sereno said. "I think that we have to face the fact that the Jurassic Park folks have to go back to the drawing board on Spinosaurus." Given its proportions, it likely wasn’t a two-legged animal on land that deftly wielded its arms. Still, he said, "it would’ve been a fearsome animal. There is no question about it. You would not want to meet this animal."