It may be surprising for some people to learn that the dino to bird theory is not supported by any fossils. Those who propose the dino to bird theory acknowledge the fact that they have never found one fossil that is on the purported line from dino to bird.
There are a number of dinosaur taxa that have been found, but it has been determined that none of them are ancestors to birds.
Even so, the dino to bird enthusiasts still imagine that birds evolved from dinosaurs.
This lack of fossils is well known but never mentioned.
All that has ever been found are dinosaur taxa that are NOT ancestors. The dino to bird theorists claim they are "sister taxa". But of course that makes no sense because there is no evidence of any actual dino to bird lineage for those sister taxa to be related to. None.
It is all imagination.