Professor
The evidence that the lines in the Sinosauropteryx fossil represent feathers is very strong. The arguments of the critics are unconvincing.

First, it is unlikely that the lines are a result of the decomposition of the dinosaur’s skin, because we don’t see any such decomposition in the fossils of other animals buried at the same site. In fact, the fossils of many other animals buried at the site show evidence that their functional skin structures have been beautifully preserved in volcanic ash. They well-preserved condition of the other fossils makes it likely that the Sinosauropteryx’s lines are also well- preserved functional structures, possibly feathers, and that they are not fibers caused by decomposition.

Second, the idea that the lines represent frills… well, there is an important chemical difference between feathers and frills. Feathers contain a great deal fo aprotein called Beta-keratin. Frills, on the other hand, do not contain beta-keratin.
Our chemical analyses suggest that the Sinosauropteryx structures did contain beta-keratin. So that indicates that the structures were feathers, not frills.

Third, feathers can be used for other functions than flight and thermoregulation. Think of a bird, like peacock, for example.
The peacock has long, colorful feathers in its tail. And it displays its tail in order to attract a mate. That’s a distinct function of
feathers called the display function. Recently, we have been able to do analyses on the Sinosauropteryx structures that show us that the structures were colorful. They were orange and white. The fact they were colorful strongly supports the idea that they were feathers that this dinosaur use for display.