A gigantic dinosaur that terrorized the Earth during the mid-Cretaceous period is not just potentially the largest predatory dinosaur that lived on Earth. It also appears to be the weirdest.

The characteristics of the 50-foot long monster called Spinosaurus aegyptiacus, which lived 95 million years ago in the mid-Cretaceous Period, is unlike those that paleontologists know of. With its front-heavy build, agile tail, flat hind feet and relatively short limbs, the animal appearS to have a body built for spending most of its time on the water, making it the first and only known dinosaur to have a semi-aquatic lifestyle.

Unlike other carnivorous dinosaurs such as the T. rex, Allosaurus and Giganotosaurus that move on two feet, the Spinosauraurus also had four legs and it is the only known quadrupedal predatory dinosaur to date.

"The animal is unlike any other predatory dinosaur. There's no blueprint for it. There's no modern-day equivalent for it. It's looking at a completely new kind of animal," Nizar Ibrahim, from the Organismal Biology and Anatomy at the University of Chicago said.

Ibrahim and colleagues who described the dinosaur in a study published in the journal Science on Sept. 11, reconstructed the animal based on newly found bone of Spinosauraurus, fossils from collections in North America and Europe, and records from the family of Ernst Stromer, the German paleontologist who was the first to find remains of the dinosaur about one hundred years ago, which were unfortunately destroyed during the war.

The humungous creature that measured about nine feet longer than the T. rex likely feasted on marine prehistoric animals. The researchers found that the creature's long and slender jaws as well as its conical teeth were adept at catching slippery fish. The sail-like structure at its back also stuck out of the water as the animal waded and swam for its prey.

Ibrahim said that the creature terrorized an immense river system in North Africa that spanned from Morocco and Egypt and while the animal may have favored feasting on car-sized fish, early crocodiles and prehistoric sharks, it is also believe to have occasionally taken down other smaller dinosaurs albeit scientists believe it is not as fast when it walked on land.

"It probably had outsized arms, with flashing scythe-like claws," said study researchers Paul Sereno, from the Organismal Biology and Anatomy, University of Chicago. "It wouldn't have been fast on land, but you would not want to encounter this animal."