New macrofossils of the Australian cycad Bowenia and their significance in reconstructing the past morphological range of the genus

Abstract

Premise of research. This study describes a new fossil species of Bowenia and reconsiders known fossil species and their evolutionary significance. Methodology. The fossils we describe here were collected for this study or were available from previous collections made over several decades. The fossils were identified by direct comparisons with extant and fossil species. Pivotal results. A reexamination of known and newly discovered Bowenia macrofossils confirms the presence of at least three fossil species in Australia. A new species, Bowenia johnsonii, is described from the southernmost location, the Early Eocene Lowana Road site in southwest Tasmania. When compared with the two extant species, the three fossil species demonstrate two distinct pinnule morphologies: relatively small with distinct serrations in Bowenia eocenica and Bowenia papillosa and larger pinnules with minute serrations in B. johnsonii. When considered together, the stomata of the extant species are denser and larger than those of the fossil taxa. Conclusions. The cycad genus Bowenia has a restricted extant distribution along the east coast of Queensland but is known more widely within Australia from fossils. The fossil record of Bowenia is important in documenting the past distribution of this genus, and aspects of its pinnule morphology provide insights into its environmental interactions. The possible relationship of the fossil Bowenia species with the Aptian Argentinian genus Eobowenia is considered, along with some fragmentary Australian fossils of probable Bowenia.