Mycorrhizal Conifer Roots From the Lower Cretaceous of the Otway Basin, Victoria

Abstract

Fossil roots with nodular and abbreviated lateral roots are described from the Devils Kitchen locality within the Lower Cretaceous Otway Group. The general morphology of these roots indicates a mycorrhizal association, the oldest such record from Australia. Based on the root morphology and associated megaflora it is considered that the roots are coniferous (Taxodiaceae or Podocarpaceae); an association of the roots with foliage of Geinitzia tetragona sp. nov., which is possibly taxodiaceous, is indicated. The major role of nodular mycorrhizal roots in extant plants is phosphate uptake which enhances minor nitrogen uptake. It is suggested that the fossil roots may have had a similar role. The Devils Kitchen locality is interpreted as a levee or near channel deposit with better drainage andlor a nutrient-poor soil relative to other soils in the sequence. The atypical plant associations of Cladophlebis australis, C. sp. b, and Geinitzia tetragona sp. nov. are a reflection of the above.