The American members of the tribe Aterpini are restricted to the Central Chilean and Subantarctic biogeographic subregions of southern South America. They include the genera Alastoropolus Kuschel, with one species (A. strumosus), and Aegorhinus Erichson ( = Micropolus Kuschel, syn. n.), with 22 species. A cladistic analysis using 44 characters from external morphology produced 14 cladograms (CI = 0.39, RI = 0.62, and 177 steps, which after successive weighting were reduced to two cladograms (CI = 0.63, RI = 0.84, and 326 steps). Alastoropolus is the sister genus to Aegorhinus, whose species are arranged according to the following phylogenetic sequence: (A. fascicularis, (A. kuscheli, (A. delfini comb. n., (A. servillei; ((A. vitulus, A. bulbifer), (A. silvicola, A. nitens, ((A. inermis, (A. oculatus, (A. opaculus, (A. nodipennis, A. ochreolus)))), (A. transandinus, (A. maestus, (A. phaleratus, (A. boviei, (A. superciliosus, (A. subplanifrons, (A. schoenherri, (A. albolineatus, A. suturalis))))))))))))))). A key and habitus drawings are provided. Biogeographic patterns exhibited by species of American Aterpini indicate that they are basically restricted to the Maule and Valdivian provinces of the Sub-antarctic subregion, with three species (A. strumosus, A. delfini, and A. vitulus) also found in the Magellanic forest province of the same subregion, and two species (A. boviei and A. phaleratus) distributed in the Central Chilean subregion.