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big, slow, pterosaurs



http://rspb.royalsocietypublishing.org/content/278/1713/1881.abstract?etoc

Palmer, C. (2011). "Flight in slow motion: aerodynamics of the
pterosaur wing", Proceedings of the Royal Society B, 278:1881-1885.

Abstract

The flight of pterosaurs and the extreme sizes of some taxa have long
perplexed evolutionary biologists. Past reconstructions of flight
capability were handicapped by the available aerodynamic data, which
was unrepresentative of possible pterosaur wing profiles. I report
wind tunnel tests on a range of possible pterosaur wing sections and
quantify the likely performance for the first time. These sections
have substantially higher profile drag and maximum lift coefficients
than those assumed before, suggesting that large pterosaurs were
aerodynamically less efficient and could fly more slowly than
previously estimated. In order to achieve higher efficiency, the wing
bones must be faired, which implies extensive regions of pneumatized
tissue. Whether faired or not, the pterosaur wings were adapted to
low-speed flight, unsuited to marine style dynamic soaring but adapted
for thermal/slope soaring and controlled, low-speed landing. Because
their thin-walled bones were susceptible to impact damage, slow flight
would have helped to avoid injury and may have contributed to their
attaining much larger sizes than fossil or extant birds. The trade-off
would have been an extreme vulnerability to strong or turbulent winds
both in flight and on the ground, akin to modern-day paragliders.