If we examine the bone structure in primate hands and bat wings and bird wings
and pterosaur wings and whale flippers and penguin flippers and horse legs and
mole forelimbs and frog legs, we find they ALL have the same bones in the same
relative positions. The standard tree diagram easily demonstrates why these
different species have this same structure. That is they have common ancestors
who possessed these structures.
Standard flawed argument of homology.
Similar features are homologous and therefore evidence of evolution.
Differentiated features are lineage-specific adaptations and therefore evidence of evolution.
For example, absence of the radius or ulna bone in one of these species would be 'evidence' that the lineage evolved to no longer rely on that bone for fitness, thus it became vestigial and eventually unexpressed.
Simply put, both the presence and absence of any feature is evidence of evolution.
If certain features are too strikingly contrasted with other members of a lineage, then a new lineage can be created for the oddball. The story will be that this lineage branched off from the others in an earlier common ancestor. (such as was done with Monotremes: platypus and echidna). The oddball characteristics themselves will be used as 'proof' of this. Any number of mystical phantom events can be conjured up to accommodate discrepant characteristics.
And if they are backed into a corner in their homology storytelling of a particular transitional sequence, evolutionists have already demonstrated they have no problem invoking mystical mutation events of the past to explain the discrepancy in alleged dinosaur-bird homology.
Embryologists and some paleontologists who oppose the bird-dinosaur link, have long numbered the digits of birds II-III-IV on the basis of multiple studies of the development in the egg. This is based on the fact that in most amniotes, the first digit to form in a 5-fingered hand is digit IV, which develops a primary axis. Therefore, embryologists have identified the primary axis in birds as digit IV, and the surviving digits as II-III-IV. The fossils of advanced theropod (Tetanurae) hands appear to have the digits I-II-III (some genera within Avetheropoda also have a reduced digit IV). If this is true, then the II-III-IV development of digits in birds is an indication against theropod (dinosaur) ancestry....
... One research team has proposed a frame-shift in the digits of the theropod line leading to birds (thus making digit I into digit II, II to III, and so forth). However, such frame shifts are rare in amniotes and—to be consistent with the theropod origin of birds—would have had to occur solely in the bird-theropod lineage forelimbs and not the hindlimbs (a condition unknown in any animal)
(From what I gather there are also many cases where otherwise homologous phenotypic traits, are developed by non-homologous genetic pathways. Apparently this is also no problem for evolution. )