Flowering Plants
The Koonwarra site in Victoria preserves the remains of a Cretaceous lake that include the oldest fossil flower in Australia: a small herb-like plant that once lived on the lakeshore. Prior to the Cretaceous, land plants were mainly mosses, lichens, ferns and gymnosperms such as Araucarian pines, conifers and ginkgos. The development of flowers during this period turned out to be very a successful evolutionary move and flowering plants or angiosperms have since adapted to occupy (and dominate) almost all available land areas.
The fossil pollen record throughout the Cretaceous and Tertiary tells us something about the evolutionary journey of flowering plants. By the end of the Cretaceous early plant families such as Winteracea, Proteacea and Nothofagus were established. Descendants of all three families remain alive today including the Mountain Pepper (Winteracea), banksias and waratahs (Proteacea), Antarctic Beech trees and Tasmania's famous deciduous native Fagus (Nothofagus).
Early flowering plant families. Top row, living examples left to right: Mountain Pepper (Tasmannia lanceolata), Silver Banksia (Banksia marginata), Tasmanian Waratah (Telopea truncata) and Fagus (Nothofagus gunnii). Bottom row, sketches of fossil pollens as they appear under the microscope, left to right: Winteracea, Proteacea, Telopea (Proteacea) and Nothofagus.
Following the mass extinction at the end of the Cretaceous flowering plants continued to evolve throughout the Tertiary. Plant groups such as the Myrtaceae (myrtles including Eucalyptus), Casuarinaceae (She-Oaks), Acacia (wattles) and Poaceae (grass) appear in the pollen record. As the Australian continent migrates north, becoming progressively dryer and more fire-prone, changes in plant communities and their distribution are observed. By the late Tertiary/Pleistocene much of the land surface is dominated by plants that cope well in arid or semi-arid conditions. Small pockets of remnant Nothofagus rainforest remain in Tasmania and some highland areas, a reminder of the once-lush forests of the past.
