UC researcher fishes for rare fossil ear bones

Dr Michael Frese, an Assistant Professor at the University of Canberra and Research Associate at the Australian Museum, discovered hundreds of fossil fish ear bones (otoliths) in the Talbragar Fish Bed near Gulgong, NSW. The fossil-rich Talbragar sediments were deposited in an inland lake during the Late Jurassic, about 150 million years ago.

Otoliths are heavily mineralised particles in the inner ear of fishes. They enable fishes to sense gravity, acceleration and deceleration, which is essential for proper balance and movement control.

Isolated otoliths are known from various fossil sites, but Jurassic fishes with their otoliths still in place are extremely rare. This gap in the fossil record makes it difficult to determine which fossil otoliths belong to which species of fish.

Dr Frese discovered the first pair of otoliths from the Talbragar Fish Bed by accident. “While drawing a beautifully preserved dragonfly wing, I noticed a small coprolite [fossilised dung]. The coprolite contained fish bones and two otoliths.”

The find prompted Dr Frese to search for otoliths in several field trips to the Talbragar Fish Bed but also in the collections of the Australian Museum and the Geological Survey of New South Wales. The search quickly produced many more otoliths, most were found isolated but some were detected in the heads of fossil fishes.

Dr Frese describes the rarity of these findings. “Until recently, only two Jurassic fishes were known worldwide to show otoliths in situ and one of these was only a head carved out from the stomach of a predatory fish.”

The discovery provides insights into the evolution the central nervous system in fishes.

All specimens found by Dr Frese were donated to the paleontological collection of the Australian Museum. The curator of the collection, Dr Matthew McCurry, stresses the importance of the collaboration. “Additions to the Australian Museum’s collection ensure that other scientists can access the specimens, helping to building a valuable resource for all researchers”.

For this study, Dr Frese worked with Dr Werner Schwarzhans (National History Museum of Denmark) and Timothy Murphy (Macquarie University, NSW). The findings of this international collaboration have been published in the renowned Journal of Vertebrate Paleontology and are available online.

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