Three new Eocene cycads from eastern Australia

Abstract

The descriptions of Pterostoma R.S.Hill, a new cycad genus with two species (P. zamiodes R.S.Hill and P. anastomosans R.S.Hill) and Lepidozamia foveolata R.S.Hill add significantly to our knowledge of the floristic components of the Australian Tertiary. Along with other reports of Tertiary cycads, the discovery of these new species supports the theory that cycads had a greater geographical range and diversity in Australia during the Tertiary than at present. The evolutionary position of Pterostoma in relation to other fossil and extant cycads is considered and it is concluded that Pterostoma represents an extinct line. The possibility that fossil cycads could be of value in biostratigraphy and in estimating palaeoclimate is discussed.