The last thing a 15-million-year-old animal ate drew attention

The discovery was announced in a study published in the Journal of Vertebrate Paleontology. 1 Researchers identified the remains of some of the fish fossils' last meals, including insect larvae, two insect wings and a bivalve mollusk, in their abdominal cavities.

"This discovery sheds light on the evolutionary history of the Osmeriformes group, which lived 11 to 15 million years ago, and provides important information about Australia's ancient ecosystems," said lead author Matthew McCurry, a palaeontologist at the Australian Museum and the University of New South Wales.

The fossils were preserved in an iron-rich mineral called goethite, and analysis using high-powered microscopes revealed that the fish's bone structures, fins, pigment cells and stomach contents were preserved in extraordinary detail.

Finding multiple specimens of the same species allowed researchers to reconstruct the species' physical appearance. While not every fossil is complete, the pieces put together give a clear picture of what the species looked like.

The fish's stomach contents also shed light on the ancient species' feeding habits. "We now know that these fish fed on a variety of invertebrates, but their most common prey was tiny ghost mosquito larvae," McCurry said.

Another important finding of the study was that the color patterns of the fish could be determined thanks to the pigment cells. Co-author of the study, Michael Frese, said that a color distribution was detected with a dark color on the dorsal (back part), a light tone on the belly and two horizontal stripes on the sides of the body.

"We have previously been able to determine the color of bird feathers through melanosomes, but this is the first time the color pattern of an extinct fish has been revealed using this method," Frese said.

These fossils also reveal that the Central Highlands of New South Wales once had a temperate rainforest ecosystem and that the biodiversity in this region was extremely rich.