Scientists Spent Three Years Secretly Excavating a Fossil Site

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Scientists from the University of New South Wales, the University of Canberra and the Australian Museum have discovered a fossil site filled with preserved animals and plants from the Miocene Epoch, keeping it secret for three years while they excavated it.

The Miocene Epoch was an era dating back between 5 million and 23 million years ago, meaning not only is the quality of these fossils incredibly rare but it’s also a goldmine of palaeontology (the study of ancient life).

Inside this treasure-trove of Miocene-era fossils, scientists have found the remains of ancient trapdoor spiders, giant cicadas and wasps in amazing quality. The site has been labelled a ‘Lagerstätte’ – that is, a site that contains fossils of exceptional quality, many of which are new to science. The findings were published in Science Advances.

The site is named McGraths Flat, located near the NSW town of Gulgong. It’s one of only a few fossil sites in Australia containing fossils of this quality, making it an exceptionally important find.

Scientists have spent the last three years excavating the secret fossil site, keeping it from the public until now. Over that three-year excavation period, scientists found thousands of fossils, including rainforest plants, insects, spiders, fish and a bird feather.

“Until now it has been difficult to tell what these ancient ecosystems were like, but the level of preservation at this new fossil site means that even small fragile organisms like insects turned into well-preserved fossils,” Says Dr. Matthew McCurry, a senior lecturer at UNSW.

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

secret fossil site
Excavation at McGraths Flat. Image: Salty Dingo, UNSW

The fossils at McGraths Flat were found within a ‘goethite’, an iron-rich rock. It’s an interesting rock to find these fossils in, as goethites haven’t been found that often containing exceptional-quality fossils.

The theory scientists are running with at the moment is that the fossils formed when iron-rich groundwaters drained into a billabong, encasing organisms in iron minerals. Evidence at the secret fossil site also indicates that the rainforest ecosystem existing at the site millions of years ago was beginning to dry.

“The fossils also preserve evidence of interactions between species,” says Dr. Michael Frese from the University of Canberra.

“For instance, we have fish stomach contents preserved in the fish, meaning that we can figure out what they were eating. We have also found examples of pollen preserved on the bodies of insects so we can tell which species were pollinating which plants.

“The discovery of melanosomes – subcellular organelles that store the melanin pigment – allows us to reconstruct the colour pattern of birds and fishes that once lived at McGraths Flat. Interestingly, the colour itself is not preserved, but by comparing the size, shape and stacking pattern of the melanosomes in our fossils with melanosomes in extant specimens, we can often reconstruct colour and/or colour patterns.”

The fossils found at the site give scientists a window into the past and a better idea of the climate of millions of years ago, filling in gaps in our knowledge.

“Australia is the most unique continent biologically and this site is extremely valuable in what it tells us about the evolutionary history of this part of the world,” added Professor Kristopher Helgen, the Australian Museum’s chief scientist and the director of the museum’s research institute.

“We love that the public is always fascinated by these fundamental human endeavours of exploration and discovery.”




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