Edmonton palaeontologist solves pterosaur pelvis puzzle

Two years after the unearthing of a puzzling fossil in southern Alberta, an Edmonton paleontologist has finally identified the mysterious bone, showing in the process thatthe winged reptile it belonged to rarely got off the ground.

The pelvis bone, discoveredby a group of University of Alberta researchersin a sandstonebone bed near Steveville in Dinosaur Provincial Park, turned out to belong to a pterosaur, an order of reptilesbestknown for the ability to fly.

Pterosaur bones are notoriously rare because the fossils are so fragilefew remain intact. When found, they are either highly fragmented or severely eroded.

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"It confused us for a long time, because it's such an unusual bone," said GregFunston, a University of Alberta PhD student in paleontology. "At every turn we would come up with an idea of whatit could have been and then some feature would tell us it was something else.

"It took a long time to figure out but it was veryrewarding because it ended up being be something really unique ... It was less frustrating than it was fascinating."

Puzzled over bizarrespecimen

For months, Funston puzzled over the bizarrespecimen trying to identify the species of animal and body partthe bone belonged to.

He initially thought the bone might belong to either a theropod dinosaur or a prehistoric bird, but nothing matched.

Finally, after detailed imagining, painstaking measurements and insightfrom his PhD supervisor, world-renowned paleontologistPhil Currie, Funstonidentified the bone as a pelvis belonging to an azhdarchid, making Funston's fossil the first its kind to be found in North America.

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This family of oddly proportioned pterosaurs had gigantic heads, long necks, and short wings.

Funston'sazhdarchid roamed the earth during the Late Cretaceous period andlikely had a wingspan of between three and sevenmetres.

Azhdarchidsincluded some of the largest known flying animals of all time.

'The smoking gun was thehind limb'

Howeverthe featuresof the pelvic bone Funston identified,such as muscle scarring, suggests his giant reptileactually spent more time walking.

"By looking at their biomechanics, we can tell these animals were probably spending a considerable portion of their time on the ground," hesaid.

"The smoking gun was the hind limb. We typically find a lot of wing and vertebral bones of these animals, so finding a pelvis became important for understanding whether these animals were spending time on the ground."

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Unlike its flying ancestors, these pterosaurs likely adapted to land travel to accommodate larger bodies but also to improve their access to prey, Funston speculates.

Sticking close to the ground or "land stalking" would have made hunting easier for these strange creatures.

The fossil is raredirectevidence that these creatures were land-bound, something that was only a hypothesis until now, he said.

"It helps confirm some ideas that have been out there," Funston said. "They were spending less time in the sky and more time on the ground.

"It was a different lifestyle than their ancestors had, and it also tells us about the animals in that region."

"The first pterosaur pelvic material from the Dinosaur Park Formation (Campanian) and implications for azhdarchid locomotion" appears in Facets, a new open-access journal from Canadian Science Publishing.

"When we think of that region,the Dinosaur Park area,we think of the major predators as the raptor dinosaurs and the tyrannosaurs, but we also have to consider that these giant flying reptiles were there as well."

"Having direct evidence of that ... I think it will help stimulate more thought on that ecosystem and how these animals were living."