Mystery of how largest carnivorous dinosaur hunted is solved by Cambridge and Oxford palaeontologists
It is the biggest carnivorous dinosaur ever discovered - beating even the mighty T. rex - but mystery has surrounded how Spinosaurus hunted.
Now palaeontologists from the universities of Cambridge and Oxford have studied the density of their bones and compared them to animals including penguins, hippos and alligators to solve the debate over whether it swam or waded in water like a heron.
They found that Spinosaurus - which lived 99 to 93.5 million years ago in what is now North Africa - and its close relative Baryonyx had dense bones that would probably have allowed them to submerge themselves underwater to hunt.
By contrast, another related dinosaur called Suchomimus had lighter bones that would have made swimming more difficult, so it is likely it waded instead or spent more time on land like other dinosaurs.
Dr Guillermo Navalón, from Cambridge’s Department of Earth Sciences, co-author of a study published in Nature, said: “There’s nothing like Spinosaurus in our modern world, but they had a number of traits that we see today in semi-aquatic animals who specialise in aquatic prey.
“Aquatic animals need to be able to control their buoyancy, but terrestrial animals don't have this problem. Because bones are mineralised tissue, controlling the rate of deposition of mineralised tissue within them is the easiest route to become denser or lighter for a land-dwelling vertebrate.
“This happened in many groups that underwent the ‘back to water’ evolutionary journey: from whales and hippopotamuses to penguins and marine reptiles that lived in the distant past.
“Spinosaurus might have moved through shallow water using a combination of ‘bottom-walking’ – like modern hippos – and side-to-side strokes of its giant tail. It probably used this means of locomotion not to pursue prey for long distances in open water, but to ambush and catch very large fish like lungfishes or coelacanths that lived in the same environment.”
Only incomplete Spinosaurus skeletons have been found, but it is thought they could grow to 15 or 16 metres (49 to 52ft) in length and weighed 6.4 to 7.5 metric tons.
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