Researchers find Spinosaurus' dense bones allowed it to hunt underwater

March 23 (UPI) -- Spinosaurus, the largest known predatory dinosaur, had bones dense enough to submerge itself to hunt, according to a study released Wednesday.

A group of paleontologists analyzed the density of Spinosaurid bones and compared them to animals such as penguins, hippos, and alligators to determine that both the Spinosaurus and close relative Baryonyx could swim and actively pursue prey in the water, they said in a paper published in Nature.

Scientists were aware that these dinosaurs, which lived in Britain during the Cretaceous period, were able to navigate water, with Sponosaurids boasting elongate jaws and cone-shaped teeth like other fish-eating predators and half-digested fish scales found in the ribcage of Baryonyx from Surrey, but some believed they did not swim well and instead waded in the water.

"We battled sandstorms, flooding, snakes, scorpions and more to excavate the most enigmatic dinosaur in the world and now we have multiple lines of evidence all pointing in the same direction -- the skeleton really has 'water-loving dinosaur' written all over it!" paleontologist and National Geographic explorer Nizar Ibrahim said in a statement.

The paper's lead author, Matteo Fabbri, said researchers sought an alternative means of identifying how the Spinosaurus and other long-extinct dinosaurs lived.

"The idea for our study was, okay, clearly we can interpret the fossil data in different ways. But what about the general physical laws?" Fabbri said. "There are certain laws that are applicable to any organism on this planet. One of these laws regards density and the capability of submerging into water."

Ultimately, they found that animals that submerge themselves underwater to find food have bones that are almost completely solid throughout while dinosaurs that live on land have hollow centers.

"The bones don't lie and now we know that even the internal architecture of the bones is entirely consistent with our interpretation of this animal as a giant predator hunting fish in vast rivers, using its paddle-like tail for propulsion," Ibrahim said.

"It will be interesting to reconstruct in a lot more detail how these river monsters moved around -- something we are already working on."