Ceratopetalum fruits from Australian cainozoic sediments and their significance for petal evolution in the genus

Abstract

Ceratopetalum Sm. fruits are characterised by 4–6 enlarged woody sepals radiating from a central disk, a semi-inferior ovary, anthers between and above each sepal and three-trace sepal venation with a prominent intra-sepal vein. Two new species of Ceratopetalum are described from fruits extracted from Australian Cainozoic sediments, C. westermannii and C. maslinensis. The presence of Ceratopetalum in Middle Eocene Maslin Bay sediments, South Australia, indicates a more widespread geographic distribution for the genus during the Cenozoic. Petally is present in one extant and two fossil species and probably represents the ancestral state despite apetally in the oldest known fossil. Petals have probably been secondarily lost in response to fruit specialisation or a change in pollinator vector.