While N.A. has had several feathered dinos discovered, it has seemed that the Mongolian-Chinese fossil record is 'richer' in these animals (going by the various news outlets.) Is that just chance? Could the environments have been different enough to spur feathers in what is today's Orient?
It's a matter of preservation.Think about it: anurognathid pterosaurs, for instance, have so far _only_ been found in the places with the very best preservation (Karabastau Fm, ?Tiaojishan Fm, Solnhofen/Eichstätt, Yixian Fm, Jiufotang Fm). Not one fragment elsewhere so far.