A 15-million-year-old freshwater fish fossil. The fish's stomach contents indicate that its diet consisted primarily of ghost flies. (Photo credit: Salty Dingo 2020)
Freshwater fish fossils dating back 15 million years found in Australia represent a completely new species previously unknown to science, and their stomachs still contain the remains of their last meal.
Fossils of the new species, named Ferruaspis brocksi, were found by paleontologists at a site in McGraths Flat, New South Wales, Australia, according to a new study published March 17 in the Journal of Vertebrate Paleontology.
The stomachs of several fish were found to contain fossilized remains of their last meal, including parts of insect larvae, two insect wings, and a bivalve (a mollusk with two joined shells, such as a mussel or oyster).
The discovery marks the first fossil of a freshwater smelt, a small silvery fish from the Osmeriformes family, found in Australia, and will help scientists determine when the fish first appeared on the big island.
“The discovery of a 15-million-year-old freshwater fish fossil gives us an unprecedented opportunity to study Australia's ancient ecosystems and the evolution of its fish, particularly the Osmeriformes group, during the Miocene epoch, 11 to 15 million years ago,” said lead study author Matthew McCurry, a palaeontologist at the Australian Museum and the University of New South Wales.
Osmeriformes is a large order of fishes that includes a variety of smelt species found worldwide in both fresh and saltwater. Smelts are fairly common in the United States, particularly in the Great Lakes, Northeast, Pacific Northwest, and Alaska, although some species are also found in inland rivers and lakes. There are at least six species of smelt in the United States, including the rainbow smelt (Osmerus mordax), Columbia smelt (Thaleichthys pacificus), and Delta smelt (Hypomesus transpacificus).
A flock of Ferruaspis brocksi in pursuit of the extinct platypus Obdurodon.
Scientists have long been interested in exactly when smelt and their relatives arrived in Australia, as the fossil record of the group of fish and their ancestors has been limited. “Without fossil data, it’s been difficult to determine exactly when this group arrived in Australia and whether it has changed over time,” McCurry said.
In a new study, scientists detail how they found the F. brocksi fossils.
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