alula

[Philidor11@aol.com]

I was looking at the Nat Geo dino pages when I saw the factoid about 
eoalulavis, the 'first skilled flier'.  I checked the name and found that it 
was the first with an alula, a tuft of feathers on the thumb, which helps 
with takeoffs, landings, and slow flight.  I thought from prior discussions 
that takeoffs and landings had something to do with wing flexibility and 
motions.  How does a tuft of feathers help with this?
Also, if I read the summary correctly (a page wouldn't open), eoalulavis was 
an enantiornithe.  Did the alula develop twice?
Thanks.