At a digging site in the Sahara desert, the paleontologist Nizar Ibrahim recently found the biggest carnivorous dinosaur fossil; the unusual Spinosaurus.

By reassembling the new bone structure that Nizar found, paleontologists can affirm that it was bigger than a giganotosaurus, Tyrannosaurus and Carcharodontosaurus. The new fossil rewrite history as the first known swimming dinosaur.  

The Spinosaurus had a wide tail that could act like a propeller, it is the most extreme aquatic adaptation ever seen in a large dinosaur. “This was basically a dinosaur trying to build a fish tail,” says National Geographic Emerging Explorer Nizar Ibrahim, the lead researcher examining the fossil.

Before founding this specimen, many scientists believed that dinosaurs didn’t go in the water, but everything discovered about Spinosaurus contradicted them. This river monster was 50-feet in length and was longer than a T-Rex. His structure of dense bones like water mammals add evidence to an argument that has raged for many years among paleontologists.

Millions of years ago in the Cretaceous period, many groups of reptiles evolved to live in sea environments, such as ichthyosaurs and plesiosaurs. However, these marine dinosaurs are on a different branch of the reptile family tree compared to true dinosaurs like Spinosaurus have long been believed to live on land. “This dinosaur was swimming,” says team member Samir Zouhri, a paleontologist at the University of Hassan II.

Spinosaurus was specialized to hunt in the water and it would have followed its prey on land. Its slender jaw was ideal for catching slippery prey, helped by its wide tail that could act like a propeller. Its palmed toes had claws set in weird angles. “Spinosaurus is even weirder than we thought it was,” says University of Maryland paleontologist Tom Holtz, who wasn’t involved with the study.

The discoveries change the history of the Sahara Desert during the prehistoric period. It was once a place rich in vegetation paved with giant rivers. The streams of water contained fish the size of cars who were prayed by the legendary Spinosaurus. 

Over a century has passed since the first partial skeleton of a Spinosaurus has been found by a German paleontologist Ernst Stromer. Unfortunately, when he brought back the bones with him in Germany, they ended up being destroyed during World War II. And now, the history of Spinosaurus finally rose back to the surface after all these years.