a ritual seat or throne. The chacmools in Tula also had an association with thrones or raised seating platforms, either in front of the throne or at the entrance to a chamber containing a throne. Two chacmools have been recovered that were associated with the Great Temple of Tenochtitlan, the Aztec capital. The first was discovered in 1943, on the junction of Venustiano Carranza and Pino Suarez, about two blocks south of the temple itself. The second chacmool was excavated in the sacred precinct. This is the only fully polychrome chacmool that has been recovered anywhere; it had an open mouth and exposed teeth and stood in front of the temple of Tlaloc, the Aztec rain god; its sculpted bowl probably received heart and blood sacrifices. This latter sculpture is by far the older of the two. Chacmools have been reported as far south as the Maya city of Quiriguá, near the Guatemalan border with Honduras. The Quiriguá chacmool most likely dated to the Postclassic period and is stylistically similar to those of Tula rather than Chichen Itza. Two chacmools were reported from Tazumal, a Maya site in western El Salvador. A chacmool was excavated at Las Mercedes in Guácimo, Costa Rica. Dating and origin The oldest chacmool ever discovered was the Terminal Classic. The form was unknown in such important Mesoamerican cities as Teotihuacan and Tikal. After the first appearance of the form, it was rapidly disseminated throughout Mesoamerica, spreading as far south as Costa Rica. Although a central Mexican origin is generally assumed, there are no antecedents pre-dating the Toltecs and the form is not present in central Mexican codices. The positioning and context of the chacmool form do have antecedents in Classic Maya art and art historian Mary Ellen Miller has argued that the chacmool developed out of Classic period Maya imagery. No central Mexican chacmool has been found that clearly predates the Chichen Itza examples. However, Tula and Chichen Itza may have developed simultaneously with rapid communication of the chacmool form from one city to the other. The wider variety of chacmool forms at Chichen Itza has also been used to support the development of the form there; no two possess identical form, dress and proportions. At Tula the chacmools have a standardised form with little variation in position or proportions. Miller has proposed that the chacmool developed out of Classic Maya iconography and underwent a