Fossil flowers and fruits of capsular Myrtaceae from the Eocene of South Australia.

Abstract

Flowers and fruits of the Myrtaceae are described from the Middle Eocene Golden Grove locality of South Australia, and the taxon is here named Tristaniandra alleyi gen. et sp.nov. Flowers are pentamerous and perigynous, with sepals, petals, and stamens inserted on the rim of a hypanthium. Filaments are basally fused to form antepetalous stamen bundles, each consisting of about 6–8 stamens. The tricarpellate ovary becomes exserted on maturation, forming a partly exserted, dry fruit with loculicidal dehiscence. These features are typical of capsular-fruited members of the Myrtaceae; in particular, taxa in the tribe Kanieae. While the characteristics of the fossils are not found within any one extant genus, the fossils show some similarity to living species of Tristaniopsis , although the staminal bundles are more comparable to those found in Tristania , which is only distantly related and has a rather different fruit. Capsular-fruited Myrtaceae are now primarily confined to Australasia, and appear to have had a Gondwanic origin in the latest Cretaceous to Paleogene. Nevertheless, as fossil flowers and fruits are rare, and infrafamilial identification of pollen and leaves is difficult, the Paleogene record of capsular Myrtaceae is largely equivocal. The Golden Grove fossils establish a record of the tribe Kanieae within Eocene coastal rainforest vegetation at paleolatitude 55°–58°S during a time of global warmth.