ISLAND RODENTS - A NEW SPECIES OF OCTODON FROM ISLA-MOCHA, CHILE (MAMMALIA, OCTODONTIDAE)

A hitherto unknown species of Octodon occurs on Isla Mocha, a small co astal island in the Valdivian rainforest zone of central Chile. The ne w Pacific degu (Octodon pacificus n. sp.) exhibits characters such as soft and long fur, long and poorly tufted tait, homodont upper dentiti on, barely reduced third lower molars, broad and asymmetrical teeth wi th long reentrant folds full of cement, all of which are considered as plesiomorphic for the genus. It is suggested that geographic isolatio n led to the preservation of primitive characters. The new species pro bably represents the sister taxon of Octodon bridgesii, one of the thr ee mainland species currently known from Chile and Argentina. The phyl ogenetic significance of the new degu is discussed.