Laventiana annectens, new genus and species: fossil evidence for the origins of callitrichine New World monkeys.

A previously unidentified middle Miocene primate from the La Venta deposits of Colombia is intermediate between squirrel monkeys (Saimiri) and callitrichines (marmosets and tamarins) in the morphology of the lower molars, mandible, and talus. Laventiana annectens is closely related to Saimiri and to Cebus (capuchin monkeys) yet resembles the probable callitrichine morphotype, demonstrating that archaic relatives of a Saimiri-like stock were suitable structural ancestors for the enigmatic callitrichines. Laventiana is also more primitive than Saimiri (= Neosaimiri) fieldsi from the same fauna, further increasing the likelihood that the latter is a lineal ancestor of modern squirrel monkeys.