It's no secret in the origins debate that transitional fossils are embarrassingly rare. While Darwin predicted they would be innumerable, blaming the incomplete fossil record for their absence in his day, only a handful of questionable examples (and even a few noteable frauds) exist.
One such questionable example is archaeopteryx, a supposed link between dinosaurs and birds. Alan Feduccia, Professor Emeritus at the University of North Carolina, is an especially vocal critic of the very idea that birds evolved from dinosaurs, and is heavily opposed to archaeopteryx being cited as a transitional form between them. He is an Evolutionist himself, but if you asked him if archaeopteryx is a valid transitional form, he'd probably sigh.
Archaeopteryx remains a transitional form at the popular level because, so far at least, nothing exists to fill the void it will leave when it is finally abandoned. The faulty claim that it is transitional highlights one of the fundamental problems with Evolution: transitional fossils, if one can claim they exist at all, are exceedingly rare.
But it also highlights just how slow Evolutionists are to catch up with the evidence. Whenever popular transitional forms are shown to not be transitional after all, Evolutionists continue to cite them over and over until something else replaces them. Then that gets refuted too, often by other Evolutionists, yet they continue to be cited as transitional. The desperate search for transitional forms is matched in tragedy only by the desperation of clinging to dead ones long after they should have been permanently laid to rest. Evolution's popularity has nothing to do with evidence.