Which subfamily of Cercopithecoids has thick enamel and low, rounded cusps on their molars?

The subfamily that has thick enamel and low, rounded cusps on their molars is the Cercopithecines. This dental morphology is well-suited for their dietary habits, which include a variety of foods such as fruits, seeds, and possibly some animal matter. The thick enamel provides durability to withstand the wear that comes from processing these tougher food items. In contrast, Colobines, another subfamily of Cercopithecoids, typically have thinner enamel and high, sharp cusps on their teeth, reflecting a diet that tends to focus more on leaves and other fibrous materials. Hominoids, which include apes and not Old World monkeys, have their own unique dental adaptations. Lemuridae, being a family of strepsirrhines, represents a different evolutionary lineage and does not share the characteristics associated with Cercopithecoids. Thus, the distinctive features of molars in Cercopithecines align with their ecological niche and dietary preferences, making them the correct answer.