Creationists, for instance, are certain that Archaeopteryx is in no sense transitional, or indicative of any transition, between reptiles and birds. However some claim that it is not transitional because it is a reptile (with hoaxed feathers) whereas most claim it is not transitional because it is NOT a reptile, but simply a bird.
The archaic ceticean Basilosaurus has been identified both as just a whale and as a marine reptile, in this case (at different times, i.e. before versus after its rear limbs were discovered) by the same individual, creationist fossil "expert" Duane Gish!
Homo erectus, albeit different examples thereof, has been classified by creationists both as an ape and as a human.
That bird has no known ancestors and birds did not arise till more than 50 million years later. There is no way it can be claimed as either an ancestor to birds or as proof of Darwinian evolution.