The alleged dinosarian ancestry of birds

The idea of dinosaurs evolving into birds has been around since 1968 when it was first proposed by Thomas Huxley. Since Huxley, the hypothesis has been going through major changes.
Even after all these years of new evidence, the interpretation is still not proven.
The presence of two new fossil species, Protarchaeopteryx and Caudipteryx, has shed little light on the topic. Depending on the bias of the interpreter, these two are either flightless birds or feathered theropod dinosaurs. The presence of short, fibrous structures on a Sinosauropteryx fossil is often interpreted as "protofeathers" despite the fact that the existence and structure of these ancestral feathers are completely hypothetical.
In another problematic find, the fossil Protoavis is considered to be more similar to modern birds than Archaeopteryx but is 75 million years older. This causes significant problems for the theropod theory because the common ancestor would need to be much older than the earlier  known dinosaur Eoraptor. The plastic nature of the evolutionary theory makes it certain that something else will be put in the role of bird ancestor if the dinosaurs don't fit.
The development of the bird lung is another major issue because no suitable ancestor exists from which the lungs could have developed. Another major question is whether birds evolved from the ground or down from the trees. Many hypotheses have been suggested, but there seems to be no solid evidence for one side or the other. The evolution of birds is an area where scientists have little to agree on. The special creation of birds and their subsequent variation explain the evident much better.