Martens resemble a cross between a fox and a mink, with bushy tails and large paws with partially retractable claws. (sciencedaily.com)
They are characterized by a rectangular head with bushy beard, mustache and eyebrows; teeth that meet in a «scissor bite»; oval and dark colored eyes; and v - shaped, natural forward - folding ears (when cropped, the ears point straight upward and come to a sharp point). (en.wikipedia.org)
A defining feature are their black bushy eyebrows that form a scowl. (mariowiki.com)