The identification of some Tertiary pollen belonging to the family Euphorbiaceae

Abstract

Five fossil pollen forms from Tertiary assemblages in southern New South Wales are shown to have botanical affinities with taxa in the family Euphorbiaceae. Careful comparison of all morphological features of fossil and extant reference pollen, and consideration of as many closely related taxa as possible has enabled these identifications to be made with confidence.

The fossil pollen forms Tricolporopollenites endobalteus and Triorites introlirnbatus match the extant Macaranga-Mallotus, and possibly other related taxa. The fossil Polyorificites oblatus is identified with the extant Longetia pollen type, i.e. Austrobuxus (Longetia) buxoides and Dissiliaria tricornis. Most of the specimens of the fossil Malvacipollis divevsus fit the extant Tetracoccus pollen type, ie. Austrobuxus (Longetia) swainii and Dissiliaria baloghioides, and only a very few have malvaceous affinities. An analysis of the exine stratification and the base of the spine is a reliable way of distinguishing spiny pollen of the Euphorbiaceae from that of the Malvaceae. The presence of Micrantheurn-Neoroepera and Alchornea (Caelobogyne) is also established in the fossil record.

Only one of the fossil taxa, Micrantheum-Neoroepeva, has living representatives in the temperate zone of Australia today, and the fossil occurs in Upper Tertiary assemblages which usually lack Nothofagus. The other four are Lower Tertiary taxa, found always in assemblages with abundant Nothofagus, and their living representatives are almost entirely restricted to the tropical phytogeographic zone of Australia. This distribution contrasts strongly with the fossil localities in southern New South Wales. Only the Alchornea fossil is a Tertiary tropical element.