The history of Cunoniaceae in Australia from macrofossil evidence

Abstract

The macrofossil record of the plant family Cunoniaceae in Australia is summarised and reviewed where necessary by using detailed studies of the morphology of extant genera. Eleven of the 26 Cunoniaceae genera are represented in the Australian macrofossil record and include leaves and leaf fragments, foliar cuticle and reproductive structures, and range from Late Paleocene to Quaternary in age. Macrofossils show that some genera had a different or more widespread distribution in Australia during the Cenozoic, with two genera (Weinmannia and Codia) having become extinct from the continent. Changes in climate, including increasing cold, frost, dryness, seasonality, or some combination of these, or a reduction in vegetation disturbance regimes (e.g. volcanism, uplifting, landslips), may be implicated in the regional or continental extinctions demonstrated by the macrofossil record. Many extant genera (Schizomeria, Vesselowskya, Callicoma, Ceratopetalum, Acsmithia, Codia) had evolved by the Early Oligocene or earlier (Eucryphia, Late Paleocene; Ceratopetalum, Middle Eocene), perhaps with generic diversification more or less complete by the end of the Early Cenozoic or earlier. A Cretaceous origin of the family is possible, and may account for its widespread distribution on Southern Hemisphere landmasses, although long-distance dispersal events are required to explain some modern geographic disjunctions.