As I detail in DA, the Johel dromaeosaurs have a large
set of arm, pectoral girdle, and trunk adaptations for advanced flight not present in Archaeoptryx, which itself
was probably a competent powered flier, not just a
glider. In no regard are the flight adaptations of the dromaeosaurs' forelimbs inferior (read the descriptions of the various Johel coracoids and study the illustrations
carefully).
Do you not mean "Jehol"?
The spherical femoral head of the type Sinornithosaurus
is pictured in the Nature description, my hi-res photos
verify it. Combined with the splayed out hindlegs of
the completely articulated spread eagled sinornithosaur later described in Nature and the presence of well developed leg wings, the burden is upon those who wish to challange
the ability of Johel dormaeosaur legs to sprawl.
Biplane, for those having trouble with basic etymology, means two(bi) wings(planes). The arrangment of the wings is not definitive. There are tandem biplanes, staggered biplanes, and so forth.
Nick Gardner