Sharovipteryx - delta-winged glider?

[Tim Williams <twilliams_alpha@hotmail.com>]

Dyke, G.J., Nudds, R.L. and Rayner, J.M.V. Flight of _Sharovipteryx 
mirabilis_: the world's first delta-winged glider.  Journal of Evolutionary 
Biology (Online Early)

Abstract: "The 225 million-year-old reptile _Sharovipteryx mirabilis_ was 
the world's first delta-winged glider; this remarkable animal had a flight 
surface composed entirely of a hind-limb membrane. We use standard 
delta-wing aerodynamics to reconstruct the flight of _S. mirabilis_ 
demonstrating that wing shape could have been controlled simply by 
protraction of the femora at the knees, and by variation in incidence of a 
small forelimb canard. Our method has allowed us to address the question of 
how identifying realistic glide performance can be used to set limits on 
aerodynamic design in this small animal. Our novel interpretation of the 
bizarre flight mode of _S. mirabilis_ is the first based directly on 
interpretation of the fossil itself and the first grounded in aerodynamics."

This paper left me a tad confused.  The authors attempt to reconstruct how 
_Sharovipteryx_ might have glided with only a hindwing slung between the 
legs and tail; but later on they state that
_Sharovipteryx_ probably needed some kind of forewing too, in order to 
balance the large hindwing surface.  If mobile, paired forewings would have 
vastly improved control during landing and gliding.  The authors concede 
that no forewing is actually preserved in the specimen, noting that the 
"sediment surrounding this region in PIN 2584/8 has been disturbed by 
preparation."  But if we don't know what kind of gliding membrane (if any) 
was connected to the front half of _Sharovipteryx_, then all bets are off.  
Maybe Sharov was right, and _Sharovipteryx_ had a membrane connecting the 
fore- and hindlimbs?

_Microraptor_ gets an honorary mention, but only in the context of early 
experimentations in hindlimb flight surfaces.

Cheers

Tim