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Ancient Fish Fossils Unearthed in New South Wales Provide Insight into Aquatic Life of the Past

Remarkably preserved fish fossils, dating back as far as 16 million years, have been found in central New South Wales, allowing researchers to glimpse the final moments of these ancient creatures.

Located at the McGraths Flat fossil site, these fossils of small freshwater fish are encased in a mineral called goethite, which has helped preserve intricate details of the specimens, including microscopic structures and even the contents of their stomachs.

Dr. Matthew McCurry, the lead author and curator of palaeontology at the Australian Museum, noted the extraordinary level of preservation, stating, “In palaeontology, we often encounter many gaps. Usually, we only find isolated bones of species, making it hard to see complete animals or even soft tissues.” The fossils belong to a newly identified species named Ferruaspis brocksi.

The discovery, highlighted in the journal Vertebrate Palaeontology, provides the first significant evidence of a fish group known as Osmeriformes, which currently includes graylings and smelts, according to McCurry.

One striking aspect of these fossils is their retention of colouration cells, known as melanophores. These cells contain tiny melanin-rich organelles called melanosomes, which are smaller than a millimeter in size. Co-author Associate Professor Dr. Michael Frese, who specializes in microscopy at the University of Canberra, remarked that these findings extend the limits of what is thought possible to preserve at a micro-level.

From the microscopic analysis, researchers discovered that these fish exhibited a counter-shaded coloration, darker on top and lighter underneath, complemented by distinctive stripe patterns along their sides. Additionally, well-preserved stomach contents, including whole antennae of phantom midge larvae and fragments of bivalves, provided insight into their dietary habits right before their demise.

Frese explained that the fish were likely thriving in an environment where they fed on abundant phantom midge larvae, suggesting they died with full stomachs during a period of ecological interaction between their lake habitat and adjacent rivers.

Dr. Alice Clement, an evolutionary biologist and palaeontologist who was not involved in the research, described the analysis of melanophores to recreate the coloration patterns of these organisms as a significant advancement in the study of fossil fishes. The study of color patterns can enhance understanding of aspects like mating behaviors, predator evasion, and camouflage in ancient species, although research in this area is still developing.

The fossilized species is named in honor of Professor Jochen J. Brocks from the Australian National University, who has conducted several significant fossil discoveries at the McGraths Flat site. McCurry emphasized that these fossils offer an exceptional opportunity to explore Australia’s ancient ecosystems and the evolutionary trajectories of its aquatic life during the Miocene epoch.

Map showing McGraths Flat fossil site in central NSW, Australia

Professor John Long, an expert in ancient fishes at Flinders University who did not participate in the study, expressed that fish fossils from the Miocene era provide a rare opportunity to explore ecosystems during significant environmental transformations, such as the expansion of deserts and the reduction of forests. “This research aids our understanding of the diversity of Australia’s unique wildlife and its evolutionary responses to climate change,” he noted.

Frese likened the process of discovering fossils at McGraths Flat to piecing together a complex mosaic, suggesting that each piece revealed more about the local environment. He stated that as researchers continued to uncover these fossils, a larger picture would emerge concerning evolutionary changes and continental shifts during this pivotal historical period.

“The time when these fish lived was a transformative era for Australia,” McCurry reflected. “This research serves as a geological narrative about the impacts of fundamental climate change on ecosystems.”

Source
www.theguardian.com