This is sort of a follow-up to "Synapsid skin" (I wouldn't mind some more feedback on that question, by the way). I have seen a few websites* on gorgonopsids stating that their skin was likely smooth, hairless, scaleless, and covered with glands and pores (This is based on a skin fossil from Estemmenosuchus). Is there really enough evidence to suggest that gorgonopsids didn't have hairy and/or scaly skin? If I'm not mistaken, gorgonopsids were more closely related to the cynodonts, some of which were most definitely hairy, than to Estemmenosuchus. Seeing as hair is probably derived from scales (unless there's some other hypothesis I'm not aware of), wouldn't a more realistic explanation be that the ancestor of Estemmenosuchus, gorgonopsids, and cynodonts had hair, which was secondarily lost in Estemmenosuchus (as opposed to a hairless, scaleless ancestor giving rise to two smooth-skinned groups and one hairy group)? If we go with this hypothesis, then there's nothing to keep us from drawing hairy gorgonopsids, is there?