Rather than this convoluted scenario, I still don't see why _Rahonavis_ couldn't just be considered a relict taxon. After all, there were long-bony-tailed birds around in the Early Cretaceous.
And Madagascar is certainly no stranger to relict faunas. -- T. Michael Keesey The Dinosauricon: http://dino.lm.com Parry & Carney: http://parryandcarney.com