Generally, when furry art conflates animals or invents parts RL animals don't have -- while claiming to represent particular species. For instance, there's no nub that protrudes between the flukes of an orca's tail, but tons of artists put one there! Another example is deer that look like wolves with sideways ears and sticks attached to their heads.

I really prefer when I can tell what species a creature is supposed to be; if I can't tell the difference between an artist's wolves, coyotes, and foxes, I'll like their art less than I otherwise would. (I say this recognizing that these distinctions are HARD to capture!)