Dinossauro aquático quebra o molde

sábado, fevereiro 20, 2010

Water-dwelling dinosaur breaks the mould

Spinosaurs' semi-aquatic habits helped them coexist with tyrannosaurs.

Matt Kaplan

Researchers have found evidence of dinosaurs that spent much of their time in water. The discovery, made by analysing oxygen isotopes found in the fossils of a spinosaur that fed on fish, shows how the dinosaur might have coexisted with other large predators such as tyrannosaurs.

Spinosaurs may have spent much of their lives in water.Marc Simonetti

The results, published inGeology by Romain Amiot at the University of Lyon in France and a team of colleagues, show that dinosaurs were not in fact restricted to land as had been previously thought1. Water-dwelling animals such as Plesiosaurus andIchthyosaurus, which although dinosaur-like in appearance, are not part of the dinosaurian lineage.

Baryonyx walkeri, from the spinosaur family, had a long, crocodile-like skull littered with iconic cone-shaped teeth. When it was found, theories swirled that with piercing teeth, rather than the serrated teeth so often found in closely related meat eaters such asTyrannosaurus rex, and a long snout, the dinosaur was a fish feeder.

Evidence of fish-eating behaviour came with the discovery of partially digested fish scales inside the fossilized gut contents within aBaryonyx skeleton unearthed in England in 1983. But the gut contents also contained dinosaur remains and other evidence since has shown that pterosaurs also formed part of spinosaur diets, muddling the issue. The lack of noticeable fins, webbing or propelling tails also did not suggest an aquatic way of life.

This led Amiot and his colleagues to look at oxygen isotopes locked away inside the enamel of the spinosaur's teeth and compare them to the oxygen isotopes found in the teeth of crocodiles and other dinosaurs, and turtle-shell fragments from the same period.

Read more here/Leia mais aqui: Nature