Life in the “dead” heart of Australia

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Spider fossil found in a new fossil site. (c) Michael FFrese. Credit: Michael Free

A team of Australian and international scientists led by Australian Museum (AM) and University of New South Wales (UNSW) paleontologist Dr Matthew McCurry and Dr Michael Frese from the University of Canberra have discovered and studied an important new fossil site in the New South. Wales, Australia, containing superb examples of fossilized animals and plants from the Miocene era. The team’s findings were published today in Scientists progress.

The new fossil site (named McGraths Flat), located in the Central Tablelands, New South Wales, near the town of Gulgong, is one of the few fossil sites in Australia that can be classified as ‘Lagerstätte’ – a site which contains fossils of exceptional quality.

Over the past three years, a team of researchers have secretly excavated the site, uncovering thousands of specimens, including rainforest plants, insects, spiders, fish and a bird feather.

Dr McCurry said the fossils formed between 11 and 16 million years ago and are important for understanding the history of the Australian continent.

“The fossils we found prove that the area was once a temperate Mesic rainforest and that life was rich and abundant here in the Central Tablelands, NSW,” said McCurry.

“Many of the fossils we find are new to science and include trapdoor spiders, giant cicadas, wasps and a variety of fish,” McCurry said.

“Until now, it was difficult to say what these ancient ecosystems looked like, but the level of conservation of this new fossil site means that even small, fragile organisms like insects have turned into well-preserved fossils,” McCurry said. .

Dr McCurry with ancient fossils found in Australia. Credit: Australian Museum

Associate Professor Michael Frese, who photographed the fossils using stacking photomicrograph and a scanning electron microscope (SEM), said the McGraths Flat fossils show incredibly detailed preservation.

“Using electron microscopy, I can image individual cells of plants and animals and sometimes even very small subcellular structures,” Frese said.

“Fossils also preserve evidence of interactions between species. For example, we have the contents of the stomach of fish preserved in the fish, which means that we can understand what it was eating. We also found examples of pollen retained on the bodies of insects so that we could tell which species were pollinating which plants, ”Frese added.

“The discovery of melanosomes (subcellular organelles that store melanin pigment) allows us to reconstruct the color scheme of birds and fish that once lived at McGraths Flat. Interestingly, the color itself is not preserved, but by comparing the size, shape, and stacking pattern of the melanosomes in our fossils with the melanosomes of existing specimens, we can often reconstruct the color and / or them. color patterns, ”Frese explained.

The fossils were found in an iron-rich rock called “goethite,” which is generally not considered a source of exceptional fossils. We believe the process that turned these organisms into fossils explains why they are so well preserved. Our analyzes suggest that fossils formed when iron-rich groundwater drained into a billabong, and a precipitation of iron minerals trapped organisms that lived or fell into the water, ”added McCurry. .

Life in the "dead"  heart of australia

Old feather from the new Australian fossil site. Credit: Michael Free

Dr McCurry said the fossilized plants and animals are similar to those found in the rainforests of northern Australia, but there were signs the McGraths Flat ecosystem was starting to dry out.

“The pollen we found in the sediment suggests that there may have been drier habitats around the rainforest, indicating a shift to drier conditions,” McCurry said.

Executive Director, Science, Royal Botanic Gardens Victoria, Professor David Cantrill, said the variety of fossils preserved, along with extraordinary fidelity in preservation, provide unprecedented insight into an important time in the past of Australia, a time when mesic ecosystems still dominated the continent.

“McGraths Flat’s plant fossils give us a window into the vegetation and ecosystems of a warmer world, which we will likely experience in the future. The preservation of plant fossils is unique and provides important information about a period when the fossil record in Australia is rather poor, ”Cantrill said.

Australian Museum chief scientist and AM Research Institute director Professor Kristofer Helgen said the fossil site brings to life a picture of the Australian hinterland that we can hardly believe that it exists.

Life in the "dead" heart of australia

Ancient fossils discovered by Australian scientists. Credit: © Salty Dingo 2020 038A7137

“Australia is the most biologically unique continent, and this site is extremely valuable in what it tells us about the evolutionary history of this part of the world. This provides further evidence of climate change and helps fill in the gaps in our knowledge of this time and region, ”Helgen said.

“AOS has a rich history of scientific expeditions and research, and we love that the public is always fascinated by these fundamental human endeavors of exploration and discovery,” added Helgen.

Fieldwork at McGraths Flat was funded by a generous donation from a descendant of Robert Etheridge, an English paleontologist who came to Australia in 1866. Etheridge joined the Australian Museum in 1887 as an assistant paleontologist and in 1895 was appointed curator of the museum.

Australian museum director and CEO Kim McKay AO said under Etheridge the AM’s collections had been significantly improved and he had also started a program of expeditions – the first being to Lord Howe Island – which continues to this day.

“There is a long tradition of important scientific discoveries at AO. It’s great to see that this continues with the work of Dr. McCurry, who is directly linked to our former paleontologist, curator and director, Robert Etheridge, ”McKay said.

Life in the "dead" heart of australia

Nothofagidites cf deminutus (F.146023-P6) polished. Credit: (c) Michael Free

McGrath Apartment

First found in 2017, McGraths Flat is named after Nigel McGrath who discovered the site’s first fossils. The site is located near Gulgong in central New South Wales (Gulgong is a Wiradjuri word meaning “deep water hole”).

The Miocene epoch (approximately 23 to 5 million years ago) was a time of immense change in Australia. The Australian continent had separated from Antarctica and South America and was drifting north. When the Miocene began, there was an enormous wealth and variety of plant and animal life in Australia. But about 14 million years ago, a sudden change in climate known as the “Middle Miocene disturbance” caused widespread extinctions. Throughout the second half of the Miocene, Australia gradually became more and more arid and tropical forests transformed into the dry shrub and desert areas that now characterize the landscape. The recently discovered fossil site, McGraths Flat, offers unprecedented insight into what Australia’s ecosystems looked like before this aridification.


Rare pig-nosed turtles once made their home in Melbourne


More information:

MR McCurry et al, A Lagerstätte from Australia provides insight into the nature of Miocene mesic ecosystems, Scientists progress (2022). DOI: 10.1126 / sciadv.abm1406. www.science.org/doi/10.1126/sciadv.abm1406

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Australian museum

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Life in Australia’s “dead” heart (2022, January 7)
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