Dr. K. A. Nowotny's note on the Xolotl figure in the Museum für Völkerkunde, Vienna raises some points of general interest. First, Xolotl is mentioned as related to Quetzalcoatl in a rather obscure way in the Codex Magliabecciano.
The writer, talking of Quetzalcoatl says: “este dizen que fue hijo de otro dios que llaman mictlan tecutli, que es sefior del lugar delos muertos. y es de otro ydolo que llaman xulutl que quiere dezir un modo de pan que ellos tienen hecho de bledos y mahiz.” In all the codices which contain the tonalpouhualli, Xolotl is given as Lord of the thirteen day period Ce Cozcaquahtli, associated with the sign of the setting sun entering the jaws of the earth. In Borbonicus, p. 26, one sees an excellent representation of Xolotl and Quetzalcoatl facing one another at a dance of the priests. In the mythological sections of Borgia, Quetzalcoatl is shown as a pair of beings descending through creation.