Dino with trick up its sleeve

September 15, 2000

Pterosaurs, the largest creatures ever to fly, used the same engineering tricks to stay airborne as Barnes Wallace's wartime bombers.

Scientists have discovered that the wing bones of the extinct reptiles possessed the same internal reinforcements as the fuselage of the Royal Air Force's Wellington Wimpy.

Lorna Steel and David Martill, palaeontologists at Portsmouth University, discovered the system of tiny cross-hatched ridges on the insides of 115 million-year-old bone fragments dug up in Brazil.

The structures would have provided vital resistance to the forces that would have acted on the pterosaur's wings while in flight.

"The pterosaurs had the same sorts of problems that face experts in aerodynamics - getting airborne and flying efficiently," Martill said.

The millimetre-scale reinforcing was discovered during a detailed analysis of the internal surfaces of fragments of well-preserved pterosaur bone not suitable for display in a museum.

It echoes the far larger geodetic cross-hatching of aluminium alloy that was used by Barnes Wallace, the inventor of the bouncing bomb, to create the Wellington Wimpy, an aircraft that was lightweight yet strong enough to carry a heavy bomb load.

Martill observed that evolution had equipped the pterosaurs similarly, making their bones light but capable of withstanding the various forces that flight exerted on them:

* The hollow wing bones, peppered with air sacs, were not circular in cross-section, but triangular, oval or "D" shaped with thickened corners. This increased their stiffness

* The bones were laminated with two directions of fibres, with the inner layer wrapped around and the outer running end to end

* Cross-struts bridged the cavities inside the bones at those points where the stresses peaked to prevent budding.

Martill and Steel's research, presented at the Symposium of Vertebrate Palaeontology and Comparative Anatomy, suggests the internal helical reinforcing is the fourth element in this natural engineering.

Steve Farrar

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