Lucario is a bipedal, canine-like Pokémon, with fur that is predominantly blue and black. It possesses a short, round spike on the back of each forepaw, in addition to a third on its chest. It has red eyes, a long snout and ears. When its mouth is open, two pairs of pointed teeth, one in the upper jaw and one in the lower, can be seen. It possesses cream-colored fur on its torso, and blue fur on its thighs that resembles shorts.
It has a medium length tail of the same blue color as well and stands on its toes rather than on its entire foot. It has developed four black appendages that hang down from its head, which rise when Lucario reads or manipulates aura, a special energy that it senses. Lucario can study this energy to predict the movements of their opponents and track their quarry. They also have the power to manipulate this energy in an offensive manner, in the form of explosive spheres of energy. Lucario can understand human speech, and have been reported to communicate with humans through telepathy.

(Source: Bulbapedia)