Sweetsops, sometimes also called Sugar-Apples, are Annona squamosa. Their fruits are sweet and good tasting, though a bit too seedy for most Northerners. Maya who take the time to work with their tongues as they eat, and spit, like them just fine.
Technically, Sweetsop fruits are "syncarps," which means that each fruit is derived from a single flower with two or more pistils, which partially fuse as the pistils mature. When the fruits are past their peak of ripeness, turn brown and start drying out, the bumps separate from one another and the fruit falls apart.
Sweetsops are native tropical American, but the Yucatan is a bit too arid for them so the Yucatan's trees are all planted.