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How Pterosaurs Terrorized the Skies

29 October 2003 (All day)
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Cretaceous ace. The large inner ear and related brain region (lower left, red) of this pterosaur implies aerial prowess, and a lowered head.

With wingspans as broad as 10 meters, pterosaurs were impressive predators. Now the first detailed x-ray images of their skulls have provided new insights to their aerial abilities, implying that they had a steady gaze and fine control of their skin-covered wings. "It's one of the most exciting pieces of work on pterosaurs in recent years," says David Unwin of the Museum of Natural History in Berlin.

It's not often that paleontologists can study the brains of pterosaurs, because the delicate skulls are usually distorted or crushed. After colleagues scanned two pristine specimens using computed tomography (CT), however, Lawrence Witmer of Ohio University, Athens, had an unvrivaled view of their anatomy. The CT scans revealed the semicircular canals of the inner ear, for example, which provide the sense of balance. The radius of the three these looping canals was quite large, which correlates with enhanced agility in modern animals.

Using the canals, Witmer was also able to figure out how the pterosaurs held their heads. One of the canals is typically horizontal when living animals are alert. This orientation of this canal in Rhamphorynchus indicates that its head was level in flight and while walking. But Anhanguera held its head downward, 30 degrees lower. That may have improved the aerodynamics of its large, crested bill, Witmer proposes. The head angle certainly would have helped Anhanguera see better while walking too, because it would allow the eyes to look ahead, Witmer says.

Witmer could also see the shapes and sizes of various lobes of the brain. That's because pterosaur brains pressed tightly against the skull, leaving an impression. Compared to birds, pterosaurs had a remarkably large flocculus. This part of the brain helps coordinate the head, neck, eyes, keeping the gaze steady while an animal moves. Why such a big flocculus? Witmer speculates that it was receiving signals from the skin covered wings, which contained muscle fibers. "It's conceivable that they've recruited the wing as a large sensory organ," he says.

"That's an important idea and a really exciting one," Unwin says. He says the potential efficiency of such a "smart wing" could help explain how giant pterosaurs were able to get off the ground.

Related sites
More about wings and maneuverability
Witmer's lab site

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