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The monophyletic and paucispecific assemblage of South American octodontid rodents has experienced an extensive adaptive radiation from above-ground dwellers to subterranean, saxicollous, and gerbil-like deserticolous life forms. The complex and saltational mode of chromosomal repatterning is the hallmark of octodontid evolution. Recent molecular evidence links this chromosome dynamics with quantum genome size shifts, and probably with reticulate evolution via introgressive hybridization in the desert dwellers T. barrerae and P. aureus. Genome duplication represents a novel mechanism of evolution in mammals and its adaptive role is reflected in the ability of deserticolous species to colonize the extreme environment of salt flats. Exclusive of Tympanoctomys, the rigid bundle of hairs behind its upper incisors is crucial to efficiently peel saltbush leaves and probably explains its broader distribution relative to P. aureus. This feature, allows efficient peeling of the saltbush leaves which in association with other atributes (ie. specialized kidneys, large bullae, feeding behavior) enabled the red vizcacha rat to cope with extreme environmental conditions (Gallardo,M, R.A.Ojeda,C. Gonzalez y C. Rios The Octodontidae Revisited. en: Contributions to honor the career of Oliver Pearson (1915-2003) (DA. Kelt, E.Lessa, JA.Salazar-Bravo y JL. Patton, eds.). University of California Publications in Zoology en prensa).