I had heard that some of the suspected basal
Dromaeosaurids were in fact, closer to birds!!! (e.g.
*Sinornithosaurus* & *Achillobator*)
_Achillobator_ is a basal dromaeosaurid? That does not appear very likely.
There is an emerging consensus that derived dromaeosaurids (including
_Velociraptor_) reversed many of the bird-like characters present in basal
dromaeosaurids (e.g., _Microraptor_, _Sinornithosaurus_). These "bird-like"
characters are actually primitive eumaniraptoran traits, and were
differentially lost in derived dromaeosaurids. _Achillobactor_, which
appears the least "bird-like" of any dromaeosaurid, might represent the
extreme end of this trend.