May 27, 2009
Giant Sauropods Held Heads High And Upright
Paleontologists reported new evidence that suggests 150 million years ago the diplodocus dinosaur may have held its impressive neck and head higher than originally thought, BBC News reported.
Mike Taylor from the University of Portsmouth and his team reshaped the dinosaur's resting pose by studying the skeletons of living vertebrates.
However, more than one theory on the sauropods' stance exists, as there is more than one way to assemble a dino-skeleton.
Dr. Taylor said he is not suggesting that museums should re-pose their long-necked sauropod skeletons from the current horizontal position to a more upright posture.
Taylor told BBC News the diplodocus in the main hall vestibule of the Natural History Museum is in a perfectly good posture.
"It's one within a whole range of movement that would have been entirely possible," he said.
However, Taylor is convinced that when they were not reaching down for a drink, the sauropods stood with their heads held very high, according to X-rays of members of 10 different vertebrate groups.
The dinosaur's high straightened necks "” much like giraffes "” would have towered up to 50 feet above the ground.
The necks of mammals and birds, which are the only modern groups that share the upright leg posture of dinosaurs, are "strongly inclined" vertically, Taylor and his colleagues found.
Taylor said the team's approach was embarrassingly straightforward.
"We looked at real animals, and at the whole animal," he said.
He explained that since bones could only offer so much information, for further study they turned to the soft tissue in the animal's huge neck, which could "enable greater flexibility than the bones alone suggest".
The first reconstructions of sauropod skeletons in the late 19th and early 20th Century were displayed with erect necks, so the idea is an old one.
Taylor said it was mostly in recent years that this view has changed and experts are now confident that they held their heads upright.
Other scientists still maintain a more horizontal view, and a recent study by Australian scientist Roger Seymour in the journal Biology Letters even suggested that the creatures would not actually be able to lift their heads up high enough to eat from tall trees, as it would raise their brains so far above their hearts that their blood pressure would have to be elevated to a dangerous and possibly lethal levels.
Dr. Taylor and colleagues remain skeptical, however.
He cited several living animals where the heart is able to exert much greater pressure than Seymour's equations predict is possible.
"We don't see why that couldn't also be true in sauropods," Taylor added.
The sauropods would likely have been able to lift their heads high, according to Paul Barrett, a paleontologist from London's Natural History Museum.
But he remains unconvinced that would have been their "resting posture" since it would require lots of muscular activity, and put a lot of strain on their hearts.
Considering it is impossible to know how thick the pads of connective tissue between the dinosaurs' vertebrae were, Barrett said it is difficult to estimate how much of a role this tissue, along with muscles and tendons, played in the animals' range of movement.
He said since there is no living animal built in the same way as sauropods, the study of living animals' skeletons is very valuable.
"Finding a model to explain the biology of these creatures is not that easy," he added.
On the Net:
- University of Portsmouth
- London Natural History Museum
- Biology Letters
- Acta Palaeontologica Polonica