Mendez XIV was a mutant leader from the Mendez Dynasty. Little is known about this mutant, except for the fact that a bust of him was constructed and placed upon a plinth within a passageway outside the mutant cathedral. 
Possibly, Mendez XIV was a biological descendant of the first Mendez who occupied the West Coast Forbidden Zone in the late 20th/early 21st century. It might also be assumed that Mendez' genealogical line extended into the 40th century, culminating with the Dynasty's final inheritor, Mendez XXVI, though whether 'Mendez' was the mutant's true birth name or merely an honorarium is unknown.
According to the 2018 novel Death of the Planet of the Apes the busts in the mutant city contained the preserved memories of its former leaders, which could be accessed through touch. That of Mendez XIV revealed the first encounter with the 'Inheritors' - who had defeated the 'Makers' - during his reign.
- The first draft screenplay for Beneath the Planet of the Apes gave an insight into the character of Mendez XIV. "Guards lead Brent down a long white corridor lined on one side by head-and-shoulder portraits - each titled and dated... We start on an antique, cracked canvas in an old-fashioned gilded frame, labelled: Mendez I: 1997-B.3. The portrait is that of a handsome, strong-jawed, dark-haired, military-moustached soldier in the 20th century uniform of a U.S. Army five-star General. His likeness survives in the portrait of Mendez II - V... As we pan past Mendez VI - XIII, a strain of no more than ordinary depravity appears to be developing in the Mendez dynasty.. coarser features, a fatter face, a weaker chin, a balder head; possible evidence of alcoholism in a bulbous nose; and of brawling, in an eye-patch. But Mendez XIII, a handsome enough rogue, must have made a good marriage; because Mendez XIV (who appears to have succeeded him when young) is of a beauty sufficiently remarkable to halt Brent in his stride. But the giant guards will brook no delay and threateningly hurry him past the remaining portraits, which are all handsome. And the new, healthier infusion into the dynastic strain survives to the last portrait of all." Of course, the reason for the sudden youthful improvement in looks is not attributable to genetics as Brent supposes, but rather to the adoption of facial masks to conceal the increasing deformaties of the mutant community. Mendez XIV, it seems, introduced this tradition.
- The Beneath the Planet of the Apes novelization as well as the final shooting script by Paul Dehn indicates that all of the bronze busts featured in the cathedral's underground causeway were those of the entire Mendez family line.
- Planet of the Apes Revisited - First Draft Screenplay at Hunter's Planet of the Apes Scripts Archive