No one actually knows for sure. The only thing we are absolutely sure of, is the fact that the fossils of their skin/scales were almost as identical to an alligators. In my personal opinion, I do not believe they were from/apart of the “bird family”, only because it just doesn’t add up, nor does it make any legitimate sense to me. :)
Hundreds of years ago, when men roamed with Dinosaurs, there were drawings/sketches/paintings against sheltered rocks and none seemed as if they were covered in feathers.
Not to mention... I don’t recall seeing any feathered beasts in Jurassic Park. ;)