Fossils of rainforest inhabitants found in Australian deserts

In the middle of the Australian desert, scientists have found fossils of flora and fauna inhabiting this area in the Miocene. The area was then a tropical rainforest. Work on the study of new species of animals and plants was published in Science Advances.

Paleontologists have found new species of flora and fauna, which inhabited Australia in prehistoric times, in a vast desert area on the Central Highlands of New South Wales. The fossilized remains of spiders, insects, fish, plants and bird feathers found here date back to the Miocene era, and range in age from 11 to 16 million years.

“The fossilized remains we found were further evidence that there was tropical vegetation here. These areas of the Central Plateau were in the temperate belt, and biological life was abundant and diverse here. Many of the fossilized animal and plant prints we found were new to science. These include spider hatchlings, giant cicadas, wasps, and various species of fish. For the first time, we were able to imagine what the prehistoric ecosystems in this area were like. Especially striking is the fact that even tiny insect organisms that lived here, turned into well-preserved fossils” – says paleontologist Matthew McCarry of the Research Institute of the Australian Museum.

The complex of archaeological and paleontological finds, called McGraths Flat, was very unusual. The sedimentary layer with fossil remains here is so unique that it even contains fragments of soft tissue of living creatures, and in some fossils there are preserved subcellular structures. Even more incredible is the fact that all the fossils were preserved in an iron-rich rock called goethite. Fossils are not usually found in these rocks.

“We believe that the process that turned these organisms into fossils is the key to why they are so well preserved. Our findings have led us to believe that the fossils came about because ferrous groundwater flowed into the swamp, and the precipitating iron minerals enveloped the organisms that lived in or fell into the water,” McCarry says.

The researchers concluded that the fossils they found resemble modern Australian rainforest ecosystems in a complex way, but there are differences in some details. For example, melanosome subcellular structures, which are responsible for tissue pigmentation, were preserved in fossilized feathers, as well as in the eyes of fish and flies. Although no pigmentation was preserved in the ancient melanosomes themselves, their structure can be compared with that of modern melanosomes to understand what shade the tissues might have had. This will allow researchers to figure out what color native animals were in ancient times.

“Fossils also hold evidence of interactions between species. For example, fish have preserved the contents of their stomachs, which means we can figure out what they ate. We also found samples of pollen preserved on insect bodies, so we could find out which species of insects pollinated different plants,” adds microbiologist Michael Frese from the University of Canberra.

According to the analysis of the pollen grains, the McGraths Flat rainforests turned into areas with an arid climate. This wasn’t a revelation; scientists have long known that global temperatures began to rise in the Miocene, and it was during this period that the Australian continent began to change from tropical thickets to deserts. As global average temperatures on Earth are also now rising, the McGraths Flat ecosystem can show us how life will change in Australia’s current rainforests in the coming years.