Earliest floral evidence for the Ebenaceae in Australia
Flowers are seldom preserved in an identifiable condition. The limited knowledge of floral structure of ancient flowering plants makes comparisons with living plants difficult, as floral structure is the basis for classification of the angiosperms. When found, fossil flowers contribute considerably to our understanding of the evolution of flowering plants1–6. The flowers described here were recovered from Upper Eocene deposits near Anglesea, Australia. They are tetramerous, unisexual, male, with 16 stamens and tricolporate pollen. These flowers, and associated ebenaceous leaves, are the oldest known remains of the Ebenaceae from Australia.
Evolution of the Australian flora through the Tertiary
The evolution of the Australian flora through the Tertiary has not been reviewed by a megafossil palaeobotanist for almost a century. Based on material available and published studies, the Australian Tertiary can be considered in three units: Eocene, Oligo-Miocene, and Pliocene. Key taxa in the Eocene includeCasuarinaceae, Proteaceae, Fagaceae, Podocarpaceae, andLauraceae. Many known Eocene deposits are interpreted as warm, humid rainforests.Oligo-Miocene floras reflect a climatic deterioration, with greater occurrence of sclerophylly and xerophylly. A reduction of tropical taxa is seen with an increase ofMyrtaceae and earliest records ofMimosaceae, Chenopodiaceae, andPoaceae. These trends continue into the Pliocene, which is not well represented in Australia.Problems needing to be addressed include the discrepancy between the pollen and megafossil records ofNothofagus, the origins of Australia's wet tropical taxa, and the role of fire in the early evolution of the Australian flora.
Eocene Angiosperm Flowers
Collections of well-preserved angiosperm flowers from the Middle Eocene of southeastern North America include a variety of morphological types. The first of these specimens to be studied extensively, a catkin, has yielded a great deal of structural information. Floral morphology, pollen morphology, and the nature of the peltate scales suggest that this catkin is allied with extant genera of the Juglandaceae. This confirms the antiquity of some of the diagnostic floral and pollen features found in extant genera of the Juglandaceae and the importance of structural information available from fossil angiosperm flowers.