"On Yaxchilan Lintel 2...are crosses with flowers and small birds terminating the arms of the crosses. V. Garth Norman collected examples of the use of cross-like forms to represent trees in his interpretation of the three-branched cross on Izapa Stela 25. He concluded that in all cases, the cross was a stylized tree. Tree symbolism appears in Maya art from the earliest period. In addition to the Izapa stela, tree images appear on Early Classic pots which illustrate royal human participation in the cosmis process. The bird-cross scepter is probably a local reference to the Axis Mundi, as is the Sarcophagus Lid at Palenque."
Carolyn E. Tate, Yaxchilan: The Design of a Maya Ceremonial City, p. 107