Leaf fossils of the ancient Tasmanian relict Microcachrys (Podocarpaceae) from New Zealand

<p><strong>Premise of the study:</strong> <i>Microcachrys tetragona</i> (Podocarpaceae), endemic to the mountains of Tasmania, represents the only remaining taxon of one of the world’s most ancient and widely distributed conifer lineages. Remarkably, however, despite its ~150 Myr heritage, our understanding of the fossil history of this lineage is based almost entirely on the pollen record. Fossils of <i>Microcachrys</i> are especially important in light of recent molecular phylogenetic and dating evidence. This evidence dates the <i>Microcachrys</i> lineage to the Mesozoic and does not support the traditional placement of <i>Microcachrys</i> as sister to the southeastern Australian genus <i>Pherosphaera</i>.</p> <p><strong>Methods:</strong> We undertook comparative studies of the foliage architecture, cuticle, and paleoecology of newly discovered fossils from the Oligo-Miocene of New Zealand and M. tetragona and discussed the importance of <i>Microcachrys</i> in the context of Podocarpaceae phylogeny.</p> <p><strong>Key results:</strong> The fossils represent the oldest and first extra-Australian macrofossils of <i>Microcachrys</i> and are described as the new foliage species <i>M. novae-zelandiae</i>. These fossils confirm that the distinctive opposite decussate phyllotaxy of the genus is at least as old as the Oligo-Miocene and contribute to evidence that <i>Microcachrys</i> plants were sometimes important components of oligotrophic swampy habitats.</p> <p><strong>Conclusions:</strong> Leaf fossils of <i>Microcachrys</i> closely comparable with the only extant species confi rm that this lineage had a much wider past distribution. The fossil record and recent molecular phylogenetic studies, including that of <i>Microcachrys</i>, also serve to emphasize the important status of Tasmania as a refugium for seed plant lineages.</p>