Miocene marmosets: First fossil evidence

The first fossil remains of marmosets, an isolated incisor, premolar, and molar, all similar in size toCallithrix species, have been discovered in the middle Miocene La Venta fauna of Colombia. The M¹ is referred to a new genus and species,Micodon kiotensis, characterized by a fully developed hypocone and low occlusal relief. The P₄ and I¹ resemble those ofCallithrix, suggesting a close affinity with callitrichin marmosets. In combining small size with a four-cusped morphology,Micodon demonstrates the shortcomings of typological definitions of platyrrhine families and suggests that small body size may have preceded the tricuspid molar pattern in marmoset evolution. The 14- to 15-Ma date for the La Venta suggests that marmosets are an at least moderately ancient radiation, contrary to estimates based upon the molecular clock.