So, let me offer another example. Brown bears and Polar bears.
They are obviously different in appearance, but more than that, there are many other differences. Polar bears have webbed feet. Polar bears have colorless fur (not white) that transmits light (and heat) to the (black) skin. Polar bears have a double coat of fur, long hair and a short, dense interior coat that is essentially, water proof, much like a duck. It is laden with oils from the skin that makes it waterproof. Polar bears lack the dished face of brown bears. Polar bears have hind legs that are proportionally longer than those of brown bears. Polar bears are generally larger than brown bears. Polar bears have smaller ears. Only Kodiak bears rival the size of Polar bears, and yet, on average, Kodiak bears are smaller. These species are distinguishable from the skeleton alone.
And yet, Brown bears and Polar bears are interfertile. And, as I understand, so are the hybrids with each other and both parent species.
So the two interfertile species are distinguishable by outward appearance as well as skeletal structure. Moreover, they have been distinguished by genetic analysis, except for the Brown bears of the ABC islands. In appearance, these bears are indistinguishable from any other Brown bear. Genetically, they are indistinguishable from Polar bears.