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A cladistic analysis of Nothofagus is presented. Comparison of potential outgroups (Fagus and Betulaceae) suggests that Fagus is most satisfactory, but clear morphological differences between it and Nothofagus support the placement of the latter in the monogeneric family Nothofagaceae. The cladistic analysis supports the four subgenera and four extant pollen groups proposed in the most recent revisions and is consistent with the extensive fossil record, although not especially supported by it. The evolution of the deciduous or evergreen habit. so long considered a singular event of importance in Nothofagus, probably occurred several times, and is an example of parallel evolution. Resolution within subgenera is not high in most cases, but subgenus Lophozonia offers a particularly interesting insight into the relationship among extant species and the role of rare long distance dispersal across significant ocean …