(zoology) Any species of the family Cercopithecidae, the Old World monkeys.
2011, Terry Harrison, Chapter 6: Cercopithecids (Cercopithecidae, Primates), Terry Harrison (editor), Paleontology and Geology of Laetoli: Human Evolution in Context, Volume 2: Fossil Hominins and the Associated Fauna, page 134,
More importantly, perhaps, is the observation that cercopithecids are significantly under-represented in the lowermost horizons of the Upper Laetolil Beds below Tuff 5.