Araucaria (Araucariaceae) species from Australian tertiary sediments — a micromorphological study

Abstract

The cuticular micromorphology of four existing and four new species of Araucaria from Australian Tertiary sediments is examined using scanning electron microscopy. Scanning electron microscopy is very useful for distinguishing species, but less successful for determining the affinities of the fossil species within the genus. Two fossil species, A. balcombensis Selling and A. hastiensis Bigwood & Hill, are closely related to the extant South American species A. araucana (Molina) K. Koch (section Columbea). Five fossil species, A. lignitici Cookson & Duigan, A. planus R. Hill, sp. nov., A. prominens R. Hill, sp. nov., A. readiae R. Hill & Bigwood and A. uncinatus R. Hill, sp. nov., are assigned to section Eutacta, but their affinities within that section are uncertain. One fossil species, A. fimbriatus R. Hill, sp. nov., cannot be placed into a section with confidence. The presence of A. balcombensis and A. hastiensis in south-eastern Australia in the early Tertiary, along with species of Nothofagus in a subgenus now restricted to South America, suggests that there may have been early Tertiary forests in Australia similar to the Araucaria araucana–Nothofagus associations found today near the tree line in the Andes. The presence of at least three Araucaria species at the late Oligocene-early Miocene Monpeelyata deposit suggests that complex araucarian forests similar to those found today in New Caledonia may have been more widespread in the region in the past.