You can find more information about Mamey Zapote here … http://en.wikipedia.org/wiki/Mamey_sapote AND here … http://www.amcostarica.com/022503.htm. (this site also has a great recipe!).

The Chico Zapote that was mentioned in a couple of comments above, also grows here in the jungles of northern Guatemala. It is a golf-ball sized fruit (although the local people tell me that the chicos used to be much much larger than they are now) with soft brown skin and a fruit that tastes like a combination of pumpkin and butterscotch with a super sticky aftertaste. This fruit comes from the tree that was, for many years, tapped to collect the sap called “chicle” which was then used to make chewing gum.

(Anne of Rainforest Recipes)