"The small cosmological backrack is portrayed three times at Yaxchilan. It is clearly shown on Step VIII of Structure 33. There the artist turned the figure of Bird Jaguar III so that the backrack is clearly displayed. The framework of the backrack consists of the Cosmic Monster with a deer-eared dragon as its front head, the tail of a caiman, and a quadripartite badge riding on the monster. In the center of the "body"of the monster is a pendant worn on many occasions, carved with the image of a profile jaguar. This monument shows Bird Jaguar IV's grandfather engaged in the cosmic pursuit of playing the ritual ballgame. His opponents were likely the Lords of the Underworld."
Carolyn E. Tate, Yaxchilan: The Design of a Maya Ceremonial City, p. 78