Deer endemic to the New World fall in two biogeographic lineages: the first, which includes genus "Odocoileus" and "Mazama americana", is distributed in North, Central, and South America, whereas the second is composed of South American species only and includes "Mazama gouazoubira". This implies that the genus "Mazama" is not a monophyletic taxon. Genetic analysis reveals high levels of molecular and cytogenetic divergence between groups of morphologically similar species of brockets ("Mazama") and suggests a polyphyletic origin. In particular, "M. americana" showed a striking kinship with "Odocoileus" on the basis of several DNA sequences, in contrast to that expected, since this "M. americana" (now "M. temama") haplotype, of Mexican origin, was not close to several Bolivian "Mazama" sequences analyzed. Thus, "Mazama" as traditionally circumscribed may not be monophyletic. These Bolivian "Mazama" species were instead grouped with "Pudu puda" and "Ozotoceros bezoarticus". This could be explained by various possibilities, among them the existence of common ancestral haplotypes among the species or the need for a revised phylogenetic tree, with revised placement into true monophyletic genera that better reflect the true ancestry.