Semi-aquatic dinosaur trumps prior assumptions
Water-friendly attributes could contradict evolution
A strange dinosaur fossil dug up in the deserts of Morocco and whose parts were flung across two continents has been reunited — and its bizarre body parts show it may be the first known semi-aquatic dinosaur.
Dinosaurs were long thought to be landlubbers. But the 95-millionyear-old Spinosaurus aegyptiacus, described in a study in the journal Science, features the first-ever dinosaur whose body evolved to live a life partly in the water and could contradict many assumptions about dinosaur evolution.
“We have to face the fact that the Jurassic Park folks have to go back to the drawing board on Spinosaurus,” study co-author Paul Sereno, a paleontologist at the University of Chicago said in reference to its duel with Tyrannosaurus rex in the film Jurassic Park III. “It was not a balancing, two-legged animal on land. It would have been something very peculiar.”
At 50 feet long, Spinosaurus was likely the largest predatory dinosaur to walk the Earth. It had a long, thin snout with conical teeth that jutted diagonally from its mouth — perfect for snapping at fish. Its nostrils were small and pushed far up on its skull — ideal for breathing while partly submerged. Odd openings at the front of the snout could have housed pressure sensors, rather like the ones on alligators and crocodiles that help them sense movement to hunt in murky water. The differences from this Spinosaurus and other theropods run from head to toe. Theropods ran on two powerful legs and had small, spindly arms. By contrast, Spinosaurus had muscular arms with bladelike claws that could have nabbed slippery fish and shorter legs that were ill-equipped to walk on land. The bones’ marrow holes were closed, making them very dense — an adaptation seen in aquatic animals like penguins to control buoyancy. Its feet were wide and flat and might even have been webbed. “It’s about time that they found a dinosaur that was semi-aquatic,” said Hans The wissen, an anatomist at Ohio Medical University who was not involved in the paper, but has studied whales’ transition from land mammals to the sea.