Shark-Eating Spinosaurus, Earliest Mammals Discovered

Scientists peeking millions of years into the past have uncovered a giant creature named Spinosaurus that dined on early sharks, and tiny squirrel-like critters that may expand the timeline for the first mammals.

The discovery in Morocco of bones from a 50-foot dinosaur with a spiny protuberance on its back suggests the largest-ever predatory animal spent much of its time in water, according to a study in the journal Science. Meanwhile, tiny skeletons found in China, reported in the journal Nature, suggest mammals existed 40 million years earlier than previously thought.

The findings open new lines of investigation for paleontologists seeking to trace the route of life on the planet. The Spinosaurus bones, for instance, offer new insight on a form of dinosaur that split its time between the land and the water, at a time in history when Morocco’s current desert landscapes were hotbeds of aquatic life.

“The animal we are resurrecting is so bizarre, it’s going to force dinosaur experts to rethink many things,” said Nizar Ibrahim, a researcher at the University of Chicago who helped discover Spinosaurus, said on a call with reporters yesterday.

Spinosaurus was nine feet longer than the biggest known Tyrannosaurus rex, and probably used its claws to slice open sharks and sawfish for meals, the scientists said.

Along with his colleagues, Ibrahim found the Spinosaurus bones in the southeastern Kem Kem region of Morocco. The researchers made inferences about its lifestyle by comparing it with notes from Ernst Stromer von Reichenbach, the scientist who first discovered fragments of the species at the turn of the 20th century and called it “spine reptile.”

Aquatic Hunter

Spinosaurus may be the only dinosaur that spent substantial time hunting and living in water, unlike the land beasts dinosaurs were thought to be, according to the report. It probably had webbed feet and a sail on its back that breached the surface while it moved through rivers and lakes.

Its ability to swim well enough to catch its prey, including armored, razor-nosed fish that grew as large as buses and the first sharks, likely made Spinosaurus slower on land, Ibrahim said. On land, the dinosaur probably lumbered on all fours, dragging its 50-foot-long body across the ground no faster than a sloth.

“One of the things we are really interested in is how exactly this animal moved,” Paul Sereno, a paleontologist at the University of Chicago and study co-author said. “It’s like working on an extraterrestrial, a very strange creature.”

About 100 million years before Spinosaurus, three newly discovered mammals, tiny creatures with slender fingers and a furry tail, lived among the trees at a time in the earth’s history when China’s rocky hills were thick with forests.

170 Million Years

The creatures suggest there was an explosion of mammals in the Late Triassic period, about 208 million years ago. Previously, the starting point for mammals had been considered to be about 170 million years ago.

The skeletons are so intact, as opposed to small shards found previously, that scientists were able to discover they had traits distinct to mammals. The new findings may cause researchers to reclassify past fossil findings that they hadn’t been certain came from mammals.

“Our new discovery not only let us know about morphology, it gave us strong evidence showing it was a mammal,” said Jin Meng a verterbrate paleontologist that works with the American Musuem of Natural History, in a telephone interview.

The idea “existed previously,” he said. “But our evidence is pretty strong.”

The creatures likely ate insects, fruit and nuts, and were spread out across the globe. The earliest fossils found of their type were in England in the early 1800s.

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