A team of palaeontologists, including three from ANU have uncovered the oldest fossilised vertebrate muscles ever discovered.
The team have mapped the musculature of an ancient fossil fish approximately 380 million years old, discovered in the Gogo Formation in the Kimberley of Western Australia.
“Gogo fossil fish are famous for their exceptional preservation,” explains Dr Gavin Young of the ANU Research School of Earth Sciences.
“They have already revealed soft tissues such as nerve and muscle cells, the oldest known vertebrate embryos, and even a preserved umbilical cord. These are all remarkable discoveries because soft tissues had never been known to preserve in such ancient fossils.”
The new study has gone beyond merely identifying soft tissues, and, for the first time, the musculature of these ancient fishes has been observed and mapped out.
“These fossils are enclosed in limestone nodules, and are normally extracted by etching in weak acid,” said Dr Young. “Numerous beautiful skeletons of extinct Gogo fishes have been prepared using this method, but it was not realised that preserved soft tissues were being destroyed in the process.”
Co-author Nicola Power discovered beautifully preserved muscle fibres in a Gogo fish specimen while completing her honours degree at the ANU Research School of Earth Sciences.
“I was amazed to see this, and immediately stopped the acid preparation” said Ms Power.
Her specimen is one of the examples illustrated in the paper, published in the journal Science.
The research team also used the European synchrotron in Grenoble, and the Heliscan micro CT scanning facility at ANU to identify muscle fibres still buried in the rock, before acid preparation had affected the specimens.
Professor Tim Senden, from the ANU Research School of Physics & Engineering where the Heliscan micro CT facility was developed, has collected, scanned and analysed many Gogo specimens.
“This site continues to amaze me,” said Professor Senden. “Each time we look there’s a new window on life long dead. Actually, what’s truly amazing to me is how much had evolved by this point in history. Apart from skin and hair, animals pretty much had it all by the end of the Devonian period.
“We were stunned to find that our ancient fossil fishes had abs!” said leading author Associate Professor Kate Trinajstic of Curtin University and a Chief Investigator on the ANU-based ARC grant for research into early vertebrate evolution.
“Abdominal muscles were thought to be an invention of animals that first walked onto the land but this discovery shows that these muscles appeared much earlier in our evolutionary history.”
The first Australian expedition to collect Gogo fossil fish in the Kimberley was led by ANU Geology Professor David Brown in 1970. Today, ANU holds one of the largest collections of unprepared Gogo nodules.
“Many of these show that soft tissue is preserved, and this is a superb resource for future research into the early evolution of all the soft tissues and organ systems of the vertebrate body,” said Dr Young.