More

    Were there rainforests in Australia’s deserts?

    Australia’s dry, red centre used to be green, according to fossil evidence of plants that thrive in rainforests. It’s the first time they’ve been noted in the Gondwanan southern hemisphere, according to an international team of researchers.

    “These fossils show that the evolutionary history of the family is much more complex than previously thought,” says Andrew Rozefelds from the Queensland Museum, lead author of a paper in the journal Historical Biology.

    The Eocene fossils, dated from 56 to 34 million years old, were from distinctive Icacinaceae fruits discovered near Lake Eyre in northern South Australia and Tasmania’s Tamar Valley.

    Icacinaceae is a flowering plant family that includes tropical vines, low shrubs and trees, with 23 known genera worldwide. Modern plants are found in tropics across southeast Asia, the central Americas, central Africa and Madagascar.

    Two species of the fruits were discovered in Australia, and combined with other leaf and fruit fossils and the pollen record suggest the continent was prehistorically dominated by rainforest communities.

    Although the plant family isn’t well known, palaeobotanists recognise its importance for understanding the history of the world’s tropical forests.

    It was a serendipitous discovery. Rozefelds spotted two specimens from Tasmania in London’s Natural History Museum, which had been collected by natural historian Joseph Milligan around the 1840s.

    Collaborating with Icacinaceae expert Greg Stull from Washington’s Smithsonian Institution, Rozefelds and colleagues matched the fossils to specimens that he had been sent many years previously from South Australia’s geological survey, which they attributed to the Phytocreneae tribe.

    It’s an example of the rich trove of biological diversity languishing in museums that can go undetected without close inspection by experts.

    Stull remarks that the new discoveries “are the first unequivocal evidence of the family from Australia and they show that at least two species occur in the continent”.

    The South Australian fossils had unique features, earning them a new genus named Machesteria australis in honour of palaeobotanist Steven Manchester from the University of Florida.

    Most Icacinaceae fossils have been dated to the Eocene, an era with warmer and wetter climates than today, with higher global temperatures. In Australia, the most closely related modern plants are limited to the tropics of northeast Queensland.

    The fossil record suggests that the family – at least the Phytocreneae tribe – might have originated in North America and Europe before diversifying and moving south.

    The latest insight, made possible by modern molecular analysis, challenges that view, the authors say, suggesting the plants were distributed more broadly by the middle of the Eocene – possibly migrating through Antarctica.

    “This suggests that the modern distribution of Phytocreneae has largely been shaped by regional extinction/extirpation since the Eucoene,” they write, “likely driven by post-Eocene climatic cooling.”

    In Australia, they say, this probably happened during the later Cenozoic as the continent became drier and cooler.

    Read science facts, not fiction…

    There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.

    Latest articles

    Physicists could do the ‘impossible’: Create and destroy magnetic fields from afar

    Home News (Image: © Shutterstock) Scientists have figured out a way to create and cancel magnetic fields from afar. The method involves running electric current through a special...

    Is belief in God a delusion?

    Home News (Image: © Shutterstock) As the pandemic raged in April, churchgoers in Ohio defied warnings not to congregate. Some argued that their religion conferred them...

    Faint ‘super-planet’ discovered by radio telescope for the 1st time

    Home News An artist's impression of the new brown dwarf BDR J1750+3809, or "Elegast." This faint, cold celestial body was detected using radio telescope observations...

    Hubble captures a black hole’s ‘shadow beams,’ yawning across space

    Home News A ring of dusty material surrounding this black hole may be casting its shadow into space, astronomers say. (Image: © NASA, ESA, STScI and...

    Related articles