Jon Barber wrote (in part):
D) It lacked an alula, which assists in low-speed flight and
maneuverability control.<
It's been my hypothesis for a long time that the aerodynamic function of
the alula could have been fulfilled by the exposed finger claws of early
birds such as Archie (see my post from several years ago at
http://dml.cmnh.org/2001Jan/msg00543.html). As I note in that post, other
vertebrate flyers without feathers (bats and pterosaurs) have/had
non-feathered leading edge protuberances (aka, claws) in approximately the
same leading edge location. It's my belief that these did/do function like
an alula. This could be tested empirically, but I haven't done it, and
neither has anyone else that I know of. Without testing this, it's
premature to dismiss low-speed flight and maneuverability control simply
because this protuberance wasn't comprised of feathers.