Im thinking that now and... a Werewolf can be considered furry art or what? lol
If they're transformed into their wolf-person form, then yeah werewolf art can be considered furry. Although "transformation" is a small often creepy fetish unto itself.
This is a lot like the "adult baby" fetish that Slayer was talking about. An even smaller niche fetish that latches onto the larger furryfandom because many many people active in said fandom are so desperate for approval of their own fetish** they'll accept anyone/thing. Which in the case of adult babies leads to oft-disturbing and unsanitary "diaper fur" subgroup.
**A lot of people in the furry fandom have a persecution complex. To the point that the term "fursecution" was created to describe this, I shit you not. Usually these days the term is used in a derisive way by furries to make fun of other furries who are whining about people not liking the fandom, so even furries have a small self-regulating outlier.