Scientists report world's 1st shark-eating semiaquatic dinosaur

Scientists on Thursday unveiled what appears to be the first truly semiaquatic dinosaur, saying the monster may have spent much of its life in Africa's ancient "river of giants," feeding on giant sharks, sawfish and lungfish and other aquatic prey.

New fossils of the massive Cretaceous-era predator, Spinosaurus aegyptiacus, revealed it adapted to life in the water some 95 million years ago, according to a report in the US journal Science that provided the most compelling evidence to date of a dinosaur able to live and hunt in an aquatic environment.

The fossils also indicated that Spinosaurus is the largest known predatory dinosaur to roam the Earth, measuring 15 meters in length, or more than 2.7 meters longer than the world's largest documented Tyrannosaurus rex.

"Working on this animal was like studying an alien from outer space," said lead author Nizar Ibrahim, vertebrate Paleontologist at the University of Chicago. "It's unlike any other dinosaur I have ever seen."

Ibrahim and his colleagues from the US, Italy and Morocco studied the new fossils uncovered in the Moroccan Sahara, including portions of a skull, axial column, pelvic girdle and limbs and compared them to earlier members of the spinosaurid family that lived on land but were known to eat fish.

The researchers also analyzed a partial Spinosaurus skull and other remains housed in museum collections around the world as well as historical records and images from the first reported Spinosaurus discovery in Egypt more than 100 years ago.

"The image that emerged ... is that of a giant, front heavy dinosaur with a series of unique adaptations," Ibrahim told reporters. "We interpret these as adaptations to a semiaquatic lifestyle and, so far, Spinosaurus is the only dinosaur that shows these adaptations."

The adaptations include a nose opening far back on the skull, allowing the animal to breathe when its head is partially submerged, as well as openings at the end of the snout that are reminiscent of ones in crocodiles and alligators, enabling them to sense movement in water, Ibrahim said.

Giant slanted teeth that interlocked at the front of the snout seemed well-suited for catching fish, and curved, blade-like claws would have been ideal for hooking or slicing slippery prey, he said.

A long neck and trunk could shift the dinosaur's center of mass forward, which made walking on two legs on land nearly impossible, but facilitated movement in water, said Ibrahim.

A small pelvis, short hind legs and big flat feet seemed to be adaptations for paddling in water, he said. Some unusually dense limb bone, more like those seen in king penguins than those found in other dinosaurs, would have allowed the creature to keep itself under the water, instead of just floating.

Even the 2.1-meter-tall sail on the back of Spinosaurus, which sets a record among dinosaurs, may in part be an adaptation to a life often spent in water, Ibrahim said, adding it would have been visible even when the animal is partially submerged, probably meant for display and communicating important information to other dinosaurs such as "not getting too close to my fishing ground."

"Taken together, these features strongly suggest that Spinosaurus is the first dinosaur that spent a significant amount of time in the water," Ibrahim said.

Spinosaurus first came to light more than 100 years ago when German paleontologist Ernst Stromer described bones of the dinosaur found in the Egyptian Sahara. These Spinosaurus fossils were displayed in a museum in Munich, Germany, but an Allied bombing raid hit the museum in 1944, destroying Stromer's Spinosaurus collection.

The new Spinosaurus fossils were discovered in the Moroccan Sahara along desert cliffs known as the Kem Kem beds. This area was once a large river system, stretching from present-day Morocco to Egypt. At the time, a variety of aquatic life populated the system, including large sharks, coelacanths, lungfish and crocodile-like creatures, along with giant flying reptiles and predatory dinosaurs.

"In the last two decades, several finds demonstrated that certain dinosaurs gave origins to birds," said co-author Cristiano Dal Sasso of the Natural History Museum in Milan, Italy. Spinosaurus represents an equally bizarre evolutionary process, revealing that predatory dinosaurs adapted to a semiaquatic life and invaded river systems in Cretaceous North Africa."