Leaf and shoot morphology of extant Afrocarpus, Nageia and Retrophyllum (Podocarpaceae) species, and species with similar leaf arrangement, from tertiary sediments in Australia

Abstract

A cuticular micromorphological study confirms the separate generic status of Afrocarpus, Nageia and Retrophyllum and increases the number of available diagnostic characters. A re-investigation of fossil species previously assigned to this complex demonstrates that in all cases the generic designation was incorrect. Decussocarpus maslinensis from Eocene sediments at Mash Bay is transferred to the new genus Willungia; specimens from Eocene sediments at Anglesea referred to Decussocarpus brownei are transferred to Smithtonia victoriensis; Prumnopitys lanceolata and specimens assigned to P. aff. tasmanica from Anglesea are combined and transferred to Smithtonia. Previously undescribed fossil specimens from Oligocene sediments in Tasmania are assigned to Smithtonia jonesii and Willungia oppositifolia. Specimens of Retrophyllum are reported from Oligocene sediments in Western Australia and Miocene sediments in the South Island of New Zealand. These new fossil genera and species demonstrate that foliage characters which are now unique to Retrophyllum among the Podocarpaceae were once more widespread, providing further evidence for the hypothesis that many podocarpaceous taxa converged towards the production of flattened short shoots to increase photosynthetic efficiency.