"...Similar in their essential features to their profile counterparts, from which the three-dimensional types seem to have been derived, and whose long vertical stacks flank the central entrance, these corner masks nevertheless present a series of traits that give this theme, so common in Maya iconography, a distinctive touch.
Thus, even though there remain nearly immutable features, such as the eyes, maxillaries, fangs (and to a lesser degree, the earplugs with their usual decorations), the nostrils with their long bone nosepieces disappear almost completely, and a peninsular trait par excellance the nose appendage becomes more and more prominent, like a trunk, usually twisting downward and then turning the tip into a kind of hook that, in the present example, is scarcely noticeable."
Paul Gendrop, "Rio Bec, Chenes, and Puuc Styles in Maya Architecture," p. 100-102.
It is interesting to compare these masks with masks from Labna, Uxmal, and Sayil representing the later Puuc style from northern Yucatan [use your browser's BACK button to return here]. Even though the elements are the same, each mask has it's own distinct personality. Gendrop writes:
"It is from this time [830 A.D.] that we see a spectacular development of the architectonic mask in the Puuc region. With the exception of the already mentioned late revivals of zoomorphic doorways, it now appears as a theme disassociated from the worship of Itzamná and becomes the only religious theme that traditionally is associated with Chac--or Chaac--the Yucatecan god of rain (an interpretation that would be worth reconsidedring, in view of the substantial differences among many of these masks)."