Wing types, Sharovipteryx, Longi

In his review on wing evolution Dietrich Schaller (1985) distinguished wing types according to function, type of wing attachment, and type of airfoil support.

Accordingly there are 'limb wings' and wings not involving limbs. The latter ones can be jointless, such as the pleural wings of Draco and kuehneosaurids, or single-jointed, such as the chitinous wings of insect flapping fliers.

What about the "enigmatic" Madygen beasts?

Sharovipteryx was an early limb-wing glider. Depending on the interpretation of wing topology it is reconstructed either with the fore- and hindlimbs connected by a wing membrane - representing the type of a 'skelobrachial glider' (sensu Schaller) - or with separate brachial (arm) wings and skelosal (leg) wings.

The latter case is discussed in particular by Dyke et al. (2006): Their modelling of the aerodynamic properties of different Sharovipteryx wing configurations demonstrates that a double delta wing morphology would have been the most advantageous for gliding (using certain input conditions based on model assumptions derived from the study of the morphology of the only fossil specimen).

Longisquama as a two-wing glider is not classified as easily. It would possess multi-segment and muli-jointed gliding wings which would constitute airfoils without further structures for support. Schaller did not consider such a configuration. Or else, it would have jointless wings comparable to the membranous muscle-supported flank wings of the gliding gecko Ptychozoon - but with the difference of being segmented, attached to the back and several times as long (minor drawbacks?).

References:

Schaller, D. (1985): Wing Evolution. In: Hecht, M.K., J.H. Ostrom, G. Viohl & P. Wellnhofer: The beginnings of birds. - Eichstätt (Freunde des Juramuseums), pp. 333- 348.

Dyke, G.J., R.L. Nudds & J.M.V. Rayner (2006): Flight of Sharovipteryx mirabilis: the world's first delta-winged glider. - Journal of Evolutionary Biology 19(4): 1040-1043.