SORDES PILOSUS AND THE NATURE OF THE PTEROSAUR FLIGHT APPARATUS

IT is now generally accepted that pterosaurs, Mesozoic reptiles, were true fliers, but the nature of their flight apparatus is still much di sputed. Evidence has been presented in favour of bird-like reconstruct ions with narrow, stiff wings free of the legs(1-6) and bat-like recon structions with extensive wings incorporating both fore and hind limbs (7-10), but the Solnhofen Limestone pterosaurs, upon which these model s are based, are not sufficiently well preserved to resolve these conf licting interpretations. Here we present a new model, founded on Sorde s pilosus from the Jurassic of middle Asia (ref. 11, and N.N.B. and D. M.U., manuscript submitted), in which exceptionally well preserved win g membranes show that the hind limbs of pterosaurs were intimately inv olved in the flight apparatus; connected externally to the main wing m embrane and internally by a uropatagium, controlled by the fifth toe. Sordes also reveals that, uniquely among flying vertebrates, pterosaur s had a structurally non-homogenous flight surface with a stiffened ou ter half and a softer, more extensible inner region.