McGraths Flats, New South Wales, Australia

The heart of Australia today is arid desert, shrublands and grasslands. Though once the region was lush, dense, temperate, mesic rainforest. In one of the grasslands of the Central Tablelands in the New South Wales (NSW) of Australia, a few hundred miles southwest of Sydney, a grassland called McGraths Flats, an exemplary fossil site, has been discovered leading to the revelation of many new species with incredible detail and resolution.

Fossils of spiders such as a new species of trapdoor spider, plants, insects like giant cicadas and wasps, a variety of fish, and a bird feather have been uncovered dating to the Miocene Epoch, roughly 11 to 16 million years ago. A period of time before the region (and Australia itself) dried out towards its modern conditions as global temperatures during the Miocene rose. There has been little evidence in Australia for this period of time, until now, which is especially relevant because the rising of global temperatures during the Miocene parallels what we are seeing in the world today with human-driven climate change in some ways. [1]

The fossil preservation at McGraths Flats is incredible, resulting in the classification of McGraths Flats as a Lagerstätte. A Lagerstatte is the designation for a sedimentary deposit in which exceptional fossils are found. Fossils so well preserved that in some cases even soft tissue is preserved, tissue which under ordinary circumstances is the first to decompose. The site of McGraths Flats has such well-preserved fossils, that both soft tissue and sub-cellular structures can still be seen.
Found in iron-rich rock called goethite, a type of rock which does not usually bear exemplary fossils, fragile organisms like insects and even a feather were preserved. In McGraths Flats there is evidence of sub-cellular structures like melanosomes. [1] These give pigment to tissue, determining the color of the feather, or the eye of a fish, for example. While the melanosome is not itself coloured, its structure does indicate color, so scientists can determine color of various creatures long-extinct.

The data at McGraths Flats is of such preservation and high-quality resolution that the stomach contents of fish were preserved, even pollen grains in bodies of insects. [1] The stomach contents of the fish tell us what they ate, giving even more information of the ecology of the region. The pollen on the other hand might be even more significant, because pollen analysis can give us climate information. It is from the pollen trapped with the insects that it was understood that the global temperature was warming during the Miocene, even that the McGraths Flats rainforest was being encroached upon by deserts in the surrounding area, as Australia itself transformed from lush and temperate to the arid continent we see today. [1]

Resources

1. Mind-Blowing New Fossil Site Found in The ‘Dead’ Heart of Australia. Michelle Starr. www.sciencealert.com. 07 Jan 2022. https://www.sciencealert.com/incredible-new-fossil-site-found-in-the-dead-heart-of-australia. Accessed 09 Jan 2022.