The mystic toad arises from the cleft in the earth monsters skull and mediates between the nether and upper worlds. A king, in turn, sits above the toad (only his crossed legs and torso are visible in this photo). Notice the round markings on the ruler's thigh, which represent decay spots. This is the sunset ruler, being swallowed by the toad and returning into the jaws of the earth. Significantly, this side of the frieze is on the westernmost panel.
The jaguar can again be seen sitting to the left of the toad. The jaguar's head is strange and hard to recognize. Joyce Kelly suggests it might be a skeletal representation.