Below Mayan half-skull mask, the skull part is naturalistically sdone and resembles some of the Crystal skulls. At right is an illustration of a crystal skull from the 1800s taken from the records of the Smithsonian Institution (as illustrated in SMITHSONIAN magazine.)
And below is a newspaper article on a giant skull found in Texas. It is once again unusually large but conforms to the ADENA type. I have heightened the contrast on the photo at the bottom.