The range of morphological variation found in conifers is the greatest of all extant gymnosperms. Previous efforts to accommodate this diversity have often been implemented without a phylogenetic framework. In order to understand better the relationships among the conifer families, phylogenetic analyses were conducted using a new data set obtained from partial rDNA LSU gene sequences. These analyses strongly support the monophyly of conifers, including Taxaceae. Within the conifers, the Pinaceae are the first to diverge, being the sister group of the rest of conifers. A newly described Australian genus Wollemia belongs to the Araucariaceae, having the closest relationship with Agathis. The Taxaceae are nested within the conifer clade and are the most closely related to the Cephalotaxaceae. The Taxodiaceae and Cupressaceae together form a monophyletic group. Cupressaceae are monophyletic and derived from within Taxodiaceae. Sciadopitys, often classified in Taxodiaceae, represents a distinct monogeneric family, Sciadopityaceae. These relationships are consistent with previous cladistic analyses of morphological and molecular (rDNA SSU, rbcL) data. The well-supported clade linking the Araucariaceae and Podocarpaceae suggests that the common ancestor of these families, both restricted today to the Southern Hemisphere, inhabited Gondwanaland.

Key words: 28S rRNA gene, Conifers, Ginkgo, phylogenetic analysis