A new species of fish that lived in Australian freshwater lakes and rivers about 15 million years ago has been named after the researcher from The Australian National University (ANU) who played a key role in its discovery.
Professor Jochen Brocks discovered several fossils of the ancient fish, named Ferruaspis brocksi, at the McGraths Flat fossil site near Gulgong in New South Wales (NSW).
"I am very proud to have this world-first discovery named after me and I thank my colleagues at the Australian Museum and the University of Canberra for bestowing this upon me. This discovery opens new avenues for understanding the evolutionary history of Australia's freshwater fish species and ancient ecosystems," Professor Brocks said.
Study lead author Dr Matthew McCurry, from the Australian Museum and UNSW Sydney, said that before this fossil discovery, scientists lacked concrete evidence to pinpoint when this group of fish arrived in Australia and how they evolved over time.
"Ferruaspis brocksi is the first fossil freshwater Australian Smelt to be found in Australia," Dr McCurry said.
"The discovery of the 15 million-year-old freshwater fish fossil offers us an unprecedented opportunity to understand Australia's ancient ecosystems and the evolution of its fish species.
"This fossil is part of the Osmeriforms fish family - a diverse group of fish species within Australia that includes species like the Australian Grayling and the Australian Smelt. But, without fossils it has been hard for us to tell exactly when the group arrived in Australia and whether they changed at all through time."
The researchers said the stomach contents of the fossilised fish is "so well preserved", scientists now have a glimpse into the behaviour of these ancient species.
"We now know that Ferruaspis brocksi fed on a range of invertebrates, but the most common prey was small phantom midge larvae. One of the fossils even shows a parasite attached to the tail of the fish. It's a juvenile freshwater mussel called a glochidium. These juvenile mussels attach themselves to the gills or tails of fish to hitch rides up and down streams," Dr McCurry said.
Professor Brocks added: "This little fish is one of the most beautiful fossils I've found at McGrath Flat, and finding the first vertebrate among the abundant plant and insect fossils was a real surprise."
The species was named Ferruaspis brocksi because it was found encased in iron-rich rock. "Ferru", from ferrum (Latin) meaning iron, and "brocksi" after Professor Brocks.
Dr Michael Frese, from the University of Canberra and CSIRO, Australia's national science agency, said that one of the most exciting aspects of the work was that they could tell the colour of the fish.
"The fish was darker on its dorsal surface, lighter in colour on its belly and had two lateral stripes running along its side," Dr Frese said.
"Using a powerful microscope, we were able to see tiny colour-producing structures known as melanosomes. Fossilised melanosomes have previously enabled palaeontologists to reconstruct the colour of feathers, but melanosomes have never been used to reconstruct the colour pattern of a long extinct fish species."
The new fossil site, named McGraths Flat, is one of only a handful of fossil sites in Australia that can be classified as a 'Lagerstätte'- a site that contains fossils of exceptional quality with remarkable detail.
"The fossils found at this site formed between 11 and 16 million years ago and provide a window into the past. They prove that the area was once a temperate, wet rainforest and that life was rich and abundant in the Central Tablelands," McCurry said.
The research is published in The Journal of Vertebrate Palaeontology.
