Muscular swimmer was one of last dinosaurs

One of the last non-avian dinosaurs on Earth was a muscular, swimming duck-billed species that paleontologists recently discovered in Spain, according to a new study that has been accepted for publication in the journal Comptes Rendus Palevol.

Co-author Jose Ignacio Canudo told Discovery News that the hadrosaur, Arenysaurus ardevoli, meaning "sand dinosaur," lived just "a few thousand years before the K/T boundary."

This was the event 65.5 million years ago that wiped out all of the world's dinosaurs, save for a group of carnivorous dinosaurs that evolved into birds.

"Arenysaurus was certainly one of the dinosaurs that might have seen the fall of the K/T asteroid and suffered the consequences," said Canudo, a University of Zaragoza paleontologist.

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He and his colleagues found the remains of the new hadrosaur in the tiny South-central Pyrenees village of Aren in Huesca, Spain. The site consists of hard sandstone, which required hours of expensive, complex stone-cutting work to excavate.

A process called magnetostratigraphy, which looks at changes in polarity of geomagnetic fields preserved in sediment sequences, was used to date the dinosaur's remains, which include the best-preserved skull for a western European hadrosaur.

Noteworthy characteristics
According to the researchers, the plant-eating dinosaur's most noteworthy characteristics were its very powerful limb muscles, situated right around where modern birds possess their flight muscles.

"Arenysaurus was a terrestrial animal, so this abnormal development was not required for flying," Canudo said, pointing out that a biomechanical study is currently underway to precisely determine how the dinosaur used these muscles.

Several possibilities are under consideration, "one being that it represented an advantage for moving in marshland where such powerful anterior limbs would help it through the mud."

Eight surprising fossil findsAnother possibility is that the dinosaur's powerful limbs improved its ability to swim.

"Arenysaurus was not a marine animal, but it lived on the coast in an area where there were islands," he explained. "The ability to swim strongly would have been an advantage for moving between the islands."

Europe at the end of the Cretaceous 60 to 65 million years ago consisted of a set of various sized islands separated from Asia by a sea.

Intercontinental bridges
Since the newly excavated dinosaur is closely related to Asian hadrosaurs, the scientists believe intercontinental bridges between Asia and Europe must have existed, at least for certain periods of time, allowing "dinosaurs to pass between them."

Hadrosaurs, such as the new species with its ability to navigate through mud and water, thrived on most continents of the northern hemisphere.

"For millions of years, until their extinction at the end of the Cretaceous, duck-billed dinosaurs, or hadrosaurs, were the world's dominant herbivores," said Mark Purnell of the University of Leicester Department of Geology.

Purnell and his colleagues are particularly interested in how the last hadrosaurs ate and otherwise behaved.

Not knowing the answers to these questions makes it difficult to understand Late Cretaceous ecosystems and how (the dinosaurs) were affected during the major extinction event 65 million years ago."

Both he and Canudo are hopeful that future studies on duck bills will reveal, as Canudo said, "whether the extinction was sudden and global, or took place over a more protracted period of time lasting several thousand years."

For now, dinosaur buffs desiring a more up close and personal look at Arenysaurus can visit a mini, shrine-like museum that's been erected at the site where the dinosaur was excavated, Blasi 3 in the village of Aren. Canudo said it features a reconstruction of the hadrosaur's bones "in the very position where we found them."

"All of this," he concluded, "forms part of the project Los Ultimos Dinosaurios Europeos, 'The Last European Dinosaurs.'"