Originally Posted by Jim_Gunn

The archeopteryx in the first link could have evolved from dinosaurs that existed before it, and probably did taking into consideration the shape of hip bone and other morphological factors. It also may have been an evolutionary dead end meaning that it was not necessarilly ancestral to modern birds. The second example is not a bird at all- the article linked uses quotes to call it a "bird"- but a flying reptile. There were a lot of flying reptiles that existed at the same time as the dinosaurs, but they weren't birds either.