With respect to the diversification of spider monkeys in Mesoamerica, Ford (2006) has recently analyzed the geographic changes that occurred in South America and the Isthmus of Panama since the late Miocene and discussed how these changes may have affected the migration of primates into Central America. She suggests that as early as 8–10 Ma, the Cordillera Oriental in Colombia and Venezuela would have been a limiting barrier for the interchange of taxa between the Amazon and the northwestern regions of Colombia and Ecuador. Under Ford’s (2006) reconstruction, when the connec- tion between South and Central America was first completed (around 3.5 Ma), the only lowland primate taxa that could have feasibly migrated into Central America would have been those already living in the Cauca and Magdalena valleys in Colombia and the Choco region. Ford (2006) suggests that subsequent to the formation of the Panamanian Isthmus, there have been two distinct migrations of spider monkeys from northwestern South America into Mesoamerica. The first migration of an initial source popula- tion of spider monkeys from Panama to the southern states of Mexico would have occurred around 2 Ma, with these diversifying into the extant forms of A. geoffroyi sensu lato. Ford (2006) also argues that A. fusciceps represents a more recent, second invasion of Ateles into Central America, particularly into the northeastern region of Panama, from northwestern Ecuador and western Colombia.