Thousands of rare and prehistoric fossils have been found in the now-dry “dead heart” of Australia. These fossils, which include spiders, small fish, and plants, date back between 16 and 11 million years ago during the Miocene Epoch when the region was full of rainforests.
The discoveries were made at a new fossil site called McGraths Flat in the Central Tablelands of New South Wales (close to the town of Gulgong). The field belonged to a farmer who reported that he found fossilized leaves and that’s how the discoveries began. This location is one of very few fossil sites in Australia that are referred to as a Lagerstätte which means that the fossils are of incredible quality.
The rock layer that contains the fossils measures between 11,000 and 22,000 square feet (1,000 to 2,000 square meters). Paleontologists have excavated a little more than 500 square feet (50 square meters) so far, so there is a lot left to uncover. The reason why the fossils are so well preserved is because they are surrounded by goethite (iron-rich rock) on top of a sandstone layer. The fossils were in a now-dry pool and surrounded by iron and additional minerals that would have fallen into the pool from basalt cliffs (this is called a billabong).
Previous fossil findings in Australia from the Miocene Epoch were mostly teeth and bones belonging to larger animals, but the new discoveries were very significant as they were much smaller creatures like insects and tiny fish, as well as rainforest plants. In an email to Live Science, Matthew McCurry, who is the curator of paleontology at the Australian Museum, stated, “This site gives us unprecedented insight into what these ecosystems were like.” “We now know how diverse these ecosystems were, which species lived in them and how these species interacted.”
The fossils were analyzed with scanning electron microscopes (SEM) which allowed the experts to see them in incredible detail, such as the subcellular structures and single cells. What’s even more amazing is that the SEM revealed what the creatures ate prior to dying (these meals included larvae, fish, and a dragonfly wing that was partly digested). The SEM revealed other interesting features like pollen grains that were attached to the bodies of insects, and a freshwater mussel that was holding onto the fin of a fish.
Additional fossils include fungal spores, pollen, flowering plants, a feather belonging to a sparrow-sized bird, and over a dozen fish specimens, as well as “a wide diversity of fossilized insects and arachnids”. There had only been four fossilized spiders found in Australia and thirteen have been discovered so far at this new fossil site. Pictures of the spider and feather fossils can be viewed here.
Based on analysis of the fossilized leaves, the experts were able to calculate that the average temperature during that time period was approximately 63 degrees Fahrenheit (17 degrees Celsius). Their study was published in the journal Science Advances.