Well.... there's that China bird/dino that National Geographic was pushing for a while...
That was a hoax perpetrated by a Chinese farmer and was discovered by scientists almost immediately. Someone (Sloan, the NG art editor) jumped the gun and published the find in National Geographic before it passed peer review. Both 'Nature' and 'Science' rejected the paper.
This fraud, perpetrated not by a scientist but by a poor farmer shows what can happen when peer review is bypassed.
BTW, the two fossils (Microraptor zhaoianus and Yanornis martini) which made up Archaeoraptor were important finds in themselves.