There are 4 kinds of apes (not counting man) alive today, but the Gibbons didn’t make it into the 1968 movie, nor as I can gather from the trailers, into the 2001 remake.
Why no Gibbons in early movie (same question for book)?
As I remember the Orangs are politicians, Gorillas soldiers and Chimps scientists. If you were going to cast the Gibbons what would they be? Athletes?
They’re probably the type of second rate people who were sent to the planet Earth in The Restaurant at the end of the Universe. That’s why they never made it in, probably were shipped off to the sun or something.
A quick Google search confirms my suspicion that gibbons (and, apparently, the siamang of Asia) are lesser apes (genus Hylobatidae) … presumably, in the Planet of the Apes universe, only the great apes (genus Pongidae) evolved into sentience.
Of course, there are four species of great apes; the missing one is the bonobo, or pygmy chimpanzee. Given that these are the apes which always get a mention in discussions of anthropoid sexuality, we can guess that, on the Planet of the Apes, bonobos are prostitutes.
They were in San Francisco and only really came out at Christmas time. They died off when the humans were put into bondage, because Yule Gibbons only ate fruits and nuts.
I would just like to point out here that the Japanese movie Time of the Apes, while not having Gibbons, does contain mandrils. I would also like to point out that without that film, it would be impossible to know “Why doesn’t Johnny Care?”