Spinosaurus fossil tail suggests dinosaurs were swimmers after all
The predator’s tail was paddlelike, with a range of motion that allowed swinging side to side
Sharp-toothed Spinosaurus didn’t just stand in the shallows to snag fish for dinner; this dinosaur may have been an excellent swimmer. Spinosaurus aegyptiacus, a new fossil discovery reveals, had a paddle-shaped tail that may have helped the predator slice through the water with the grace of a crocodile.
The fossilized tail, unearthed from 95-million-year-old rocks in Morocco, is the most complete Spinosaurus tail ever recovered. Its unusual shape suggests that this dinosaur may have been aquatic — contrary to prevailing wisdom that dinosaurs were solely land dwellers, researchers report in a study published online April 29 in Nature.
“It was basically a river monster,” says Nizar Ibrahim, a vertebrate paleontologist at the University of Detroit Mercy who led the study.
“When I first saw the illustrations of the tail, I literally giggled with surprise and delight — and I’m not someone who usually giggles,” says Matthew Lamanna, a vertebrate paleontologist at the Carnegie Museum of Natural History in Pittsburgh, who reviewed the paper for Nature. “The tail was just so awesomely weird-looking for a predatory dinosaur. I’d never seen anything like it.”
Spinosaurus was known to have lived near the water and to have dined on seafood: The animal’s cone-shaped teeth would have been adept at snagging slippery fish. “But for most people, the model they were more comfortable with was a wading dinosaur that waited for the fish to swim by,” the way a grizzly bear may splash into the water to catch a fish, Ibrahim says.
Ibrahim has previously proposed that Spinosaurus was more than an occasional wader. In a 2014 paper in Science, he and colleagues reported that the creature had denser bones than most other theropods, the branch of predatory dinosaurs that includes Tyrannosaurus rex and Allosaurus (SN: 9/11/14). Denser bones could be an evolutionary adaptation to a more aquatic life, allowing for greater buoyancy control.