Sordes pilosus and the nature of the pterosaur flight apparatus

A pterosaur model based on Sordes pilosus, a Middle Asian pterosaur from the Jurassic era, reveals well conserved wing membranes that indicate close involvement of the wind limbs of pterosaurs in the flight apparatus. The link limbs are joined externally to the primary wing membrane and are linked internally through a uropatagium that is supported by the clawless fifth toe. The Sordes model reveals that the structurally non-homologous flight surface of pterosaurs, which is unique among flying vertebrates, has a stiffened outer region and a soft, flexible inner region.