Tim Williams and myself have suggested the possibility *Rapator* repr= esents a pdI-1 phalanx of an alvarezsaurian (possibly a mononykid=2C based = on morphology=2C but this is even more far-fetched due to biogeography reas= ons).
A mononykine would be far-fetched, but an alvarezsaurid in general would not be -- South America and Australia weren't isolated from each other.