Fossils of flowers, fruits and leaves have been found in Patagonia, Argentina, and have been identified as being from the eucalyptus, dating back to 51.9 million years ago. This makes them the world’s oldest scientifically validated eucalyptus macrofossils and the only ones conclusively discovered and identified outside of Australasia.
The researchers identified a series of fossils characteristic to the genus eucalyptus in the shape of imprints. Some of the key characteristics include long, thin leaves with smooth edges, dots on the leaves that reveal the plants oil glands, and scars on the fruits from where petals and sepals have fallen off.
Historically, only a small number of researchers have claimed to identify eucalyptus fossils from South America, and many of those records failed to hold up to modern scientific examination and were therefore not scientifically validated. Maria A. Gandolfo, a senior research associate from the Department of Plant Biology at Cornell University said, “The genus eucalyptus is restricted to Australia and a few surrounding islands, and it is completely extinct in South America, which makes this discovery very significant not only for botanists and paleobotanists, but also for [its] biogeographical implications”.
Patagonian eucalyptus dominated volcanically disturbed areas neighbouring standing rainforest surrounding an Eocene caldera lake. The fossils were found at a site called Laguna del Hunco, situated in the Chubut Province in Patagonia. The Patagonia region, located at the southern tip of South America, straddles both Argentina and Chile.