"It is a true transition form , but the argument is whether several different reptile-bird transitionals evolved and which one actually is the ancestor of the birds ."
"Actually , no . A specific fossil can not be , and probably will never be , identified as the ancestor of birds with any certainty . It is doubtful that the fossil record will ever be so complete as to make that possible . Your remark tends to support the confusion of creationists . They tend to represent the idea of a transitional as ancestral . Since the ancestral status of any particular fossil ca n't be acertained for any given fossil , and since any given fossil is usually placed in one of the major taxonomic groups , creationists feel justified in claiming that it is just a bird - thus , no transitionals exist . But if you look at life you will see that it is like a bush with many branches . What is being discovered in China is part of the bush that was the lineage from theropod to avian , as was Archaeopteryx . That bush is what is expected from evolutionary theory . There are several fossils that show a progression from dinosaur to bird . We do n't expect a ladder-like chain of a single lineage that evolved until a point that it branched into the birds . There are many lines along that path that went no where but were similar to the one that became the birds ."
"the argument is whether several different reptile-bird transitionals evolved and which one actually is the ancestor of the birds ."
"Actually , no . A specific fossil can not be , and probably will never be , identified as the ancestor of birds with any certainty ."