When found, the stone measured nearly twelve feet across and was called the Sun Stone since it was believed to depict the face or mask of the sun god, Tonatiuh, which was at the center of the stone. It has also been called the Calendar Stone because time was a dominant feature on the stone. One of the circular bands records the signs for the twenty days of a month and the motifs at the center part of the stone depict the Aztecs' five historical ages or eras.

An alternative to the Sun Stone/Calendar Stone theory was that of the theory proposed by Richard Townsend. Using information obtained from research done since 1978 at Tenochtitaln's principal temple - Temple Mayor. Townsend believes the face or mask in the center of the stone represents the earth monster, Tlaltecuhtli, rather than the sun god.

The Earth Monster is often depicted in Aztec inscriptions as having a gaping, toothy mouth at the center of the Earth where he is consuming blood sacrifices.

Does anyone know if there has been any more research on the Stone?