Despite old, out-of-date drawings of long-necked dinosaurs wading in
swamps, scientists have long believed that dinosaurs were a land-loving
bunch: None were thought to swim. Now, though, a new tail fossil found
in Morocco reveals that the sharp-toothed and fearsome Spinosaurus aegyptiacus was the Michael Phelps of the Cretaceous.
The predatory Spinosaurus,
which could grow up to 23 feet (7 meters) long, had a broad,
paddle-like tail that behaved more like the tails of today's crocodiles
than that of other carnivorous dinosaurs, researchers reported today
(April 29) in the journal Nature.
"This discovery is the nail in the coffin for the idea that non-avian dinosaurs
never invaded the aquatic realm," Nizar Ibrahim, a paleontologist at
the University of Detroit Mercy and the lead author of the new study, said in a statement.
"This dinosaur was actively pursuing prey in the water column, not just
standing in shallow waters waiting for fish to swim by."
Swimming spinosaurids
Spinosaurus has always been a controversial creature. It was a
theropod, or part of a group of mostly carnivorous dinosaurs that walked
on two legs; and it was around the size of another theropod, Tyrannosaurus rex,
with massive projections of its vertebrae towering up to 5.4 feet (1.6
m) above its back. Paleontologists think these projections probably
supported a skin-covered sail. Given its long snout and cone-shaped
teeth, which look much like modern crocodiles', paleontologists have
long been confident that Spinosaurus ate fish, but most suspected that it waded along shorelines, hunting in shallow waters.
Ibrahim and his colleagues thought Spinosaurus was more than just a wader. In 2014, the researchers published a paper in the journal Science
arguing that the dinosaur was adapted for a heavily aquatic lifestyle.
It had flat feet and nostrils high on its head, as well as dense bones
that would have allowed it to control its buoyancy while swimming, they wrote at the time. But, they wrote in the new Nature paper, this idea was challenged, especially because there was no evidence to show how Spinosaurus would have propelled itself through water.
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