The fossil record of Icacinaceae in Australia supports long-standing Palaeo-Antarctic rainforest connections in southern high latitudes

ABSTRACT

Fossil fruits of Icacinaceae are recorded from two Cenozoic sites in Australia, at Launceston in northern Tasmania and the Poole Creek palaeochannel in northern South Australia, representing the first report of fossil Icacinaceae from Australia. The Launceston material includes two endocarps with broad surface pits/tubercles and is referred to Palaeophytocrene. It is interpreted to have a minimum middle to late Eocene age. Two specimens are recorded from the Poole Creek palaeochannel; a mid-Miocene or middle Eocene age is possible for this site, but the older age (middle Eocene) is considered more likely. These specimens represent partial endocarps, one documenting the wall thickness and internal structures of the endocarp, and the other documenting the morphology and dimensions of the endocarp surface pits. The combination of characters shown by these fossils is unique among extant and fossil Icacinaceae genera, warranting the recognition of a new genus, Manchesteria gen. nov. These fossils document an early Cenozoic history for the Phytocreneae (Icacinaceae) in Australia and provide additional evidence that the family was broadly distributed during the globally warm Eocene. Along with recently documented African and South American fossil records, these fossils indicate a significant but little understood Gondwanic history for the family.

KEYWORDS:

• Australia
• Cenozoic
• endocarp morphology
• Icacinaceae
• Phytocreneae

Acknowledgments

Andrew Rowett and Lyn Broadbridge provided access to silcrete material held in the Geological Survey South Australia. Geoff Thompson undertook the montage photography and we are grateful for his help in providing exquisite images of the silcrete specimens from South Australia. We thank Steve Manchester for his advice and interest in progressing this research, and for his help with imaging modern fruit material of Icacinaceae. We also thank curators at the following herbaria for providing access to modern comparative specimens: BRI, K, L, MO, P, WAG. DRG’s participation was in part funded by grants from the Australian Research Council (to DRG, N. Alley and A. Rowett) and the Natural Sciences and Engineering Research Council of Canada (DG 311934). The original collection of the Poole Creek specimen was made while DRG was employed at the former South Australian Dept. of Mines and Energy, and he thanks Neville Alley and Roger Callen for assistance and advice on the stratigraphy of the Lake Eyre Basin silcrete floras.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Australian Research Council; Natural Sciences and Engineering Research Council of Canada [311934].