Dinosaur Larger Than T-Rex Was a Great Swimmer, Ate Sharks

Image: National Geographic

The dinosaur Spinosaurus aegyptiacus enjoyed surf with its turf since a new study has found this dino was a skillful swimmer that ate sharks and other marine life, sported an eye-catching sail, and was the biggest carnivorous dinosaur ever known.

The 44,000-pound 50-foot-long beast, described in the latest issue of the journal Science, measured more than 9 feet longer than the world's largest documented T. rex specimen.

Spinosaurus' size and big teeth alone would have drawn attention to the dinosaur during its lifetime 95 million years ago. The Cretaceous dino's large, and possibly multicolored, sail added yet another dramatic feature to its presence.

"The sail must have played an important function—after all, this is a very, very big thing to carry around on your back!" lead author Nizar Ibrahim told Discovery News. "We think that the sail served as a display structure, as it would stick out of the water even when the dinosaur was swimming at the surface, with most of its body submerged."

"The sail would tell other dinosaurs, and especially other Spinosaurus, a lot about the size of the animal, and may have conveyed other information, such as gender, but we don't know that for sure," continued Ibrahim, a paleontologist at the University of Chicago. "Dinosaurs had pretty good eyesight, so it is quite likely that many were brightly colored. The sail of Spinosaurus is a great 'canvas,' so I would expect it to be multicolored."

The huge dinosaur was first discovered in the Egyptian Sahara more than a century ago by German paleontologist Ernst Freiherr Stromer von Reichenbach. The remains were brought to Munich's state paleontology museum, but were later destroyed during the April 1944 allied forces bombing of parts of Munich.

Ibrahim managed to track down Stromer's surviving notes, sketches and photos at the Stromer family castle in Bavaria. With an international team of researchers that included paleontologist Paul Sereno, he found additional fossils for Spinosaurus in the Moroccan Sahara along desert cliffs known as the Kem Kem beds. During the dinosaur's lifetime, this region was once a large river system, stretching from present-day Morocco to Egypt.

CT scanning and digital modeling determined that Spinosaurus was built for both land and marine life. Adaptations for swimming included dense bones similar to those of penguins and sea cows, feet with flat and broad claws that might have been used like paddles, a flexible tail that likely helped with propulsion in water, and much more.

Its crocodile-like head, long neck, and trunk shifted the dinosaur's center of mass forward, such that the dinosaur looked "like a duck with the tail of an alligator attached to it," according to Sereno.

"The jaws of Spinosaurus were long and slender, with big conical teeth," Ibrahim said. "Perfect tools to catch slippery prey—fish, turtles, etc. The Kem Kem was a huge river system, full of big sawfish, lungfish, a car-sized coelacanth and several sharks. Those are the kinds of animals Spinosaurus would have preyed on."

After grabbing a victim with its long teeth, the dinosaur would then "either swallow its prey whole or slice it into smaller pieces with its powerful arms and large claws."

As a top predator in what Ibrahim said was "the lost world of African dinosaurs," Spinosaurus had no direct rivals, but likely would have avoided confrontations with the other T. rex-sized carnivorous dinosaurs in the area.

Evidence suggests that Spinosaurus was not the only dinosaur in the world that willingly ventured into water. For example, Scott Persons of the University of Alberta discovered scratches that, he said, were left behind by the feet of a two-legged dinosaur doggy-paddling in a Chinese river 100 million years ago.

Persons explained, "The dinosaur's claw marks show it was swimming along in this river and just its tippy toes were touching the bottom."

The fossil record for this and other swimming dinosaurs, including Spinosaurus, is incomplete. It is therefore unclear if any of these animals evolved into fully aquatic species that might have survived the Cretaceous-Paleogene extinction event 66 million years ago.

The possibility is "very, very unlikely," according to Ibrahim. He said, "We don't have any evidence for little mini Spinosaurus surviving the extinction event."

Dinosaur buffs, however, can visit a new exhibit on Spinosaurus that opens September 12 at the National Geographic Museum in Washington, D.C.

This article originally published at Discovery News here