BURIED beneath a dirt road in the middle of the state's central tablelands lie thousands of our ancestors.
About 370 million years ago, a billabong teaming with ancient fish dried up, preserving an ancient aquaria in layers of earth.
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Fish fossil fun in NSW
Dr Alex Ritchie, palaeontologist, showing how there are still many fish fossils to be found in near Cowra from the Devonian Period 380 million years ago.
When an Australian Museum paleontologist, Alex Ritchie, excavated the road in 1993 he unearthed 80 tonnes of material and discovered 4000 fish of eight different species, making the site one of Australia's richest fossil deposits.
''I knew we were onto a good thing,'' Dr Ritchie said. ''[Because] within three hours of digging along the road we hit a layer of fish.''
New research suggests the site, 10 kilometres west of Canowindra, could contain some of the most complete fossils of the first vertebrates to walk on land - a group known as tetrapods.
''If tetrapods turned up at Canowindra it would likely revolutionise our understanding of the water-to-land transition, '' a leading Swedish paleontologist, Per Ahlberg from Uppsala University, said.
But to the dismay of many Australian and international fossil scientists not a single rock has been excavated in the 20 years since Dr Ritchie's 10-day expedition.
Without the support of the country's largest natural history museum, the site has remained closed, he said.
The Cabonne Shire Council established a regional museum for a small proportion of the specimens, but it did not have the resources or expertise to develop the site further, Dr Ritchie said. ''The Canowindra community can't understand why the Australian Museum doesn't support this unique natural resource,'' Dr Ritchie said. More than 40 tonnes of fossil rocks were stored underneath the town's sports stadium because there was no where to keep them, he said.
Professor Ahlberg said the Canowindra billabong was one of the world's most important Devonian fossil fish sites, home to four fish species that evolved into land walkers.
In Poland in 2010, he found early tetrapod footprints made 20 million years before the site at Canowindra.
''That suggests that [tetrapods] would have had time to spread around the world by the time the Canowindra billabong was drying out,'' Professor Ahlberg said.
If tetrapods were found at the site they would likely be in excellent condition, possibly complete skeletons, and some of the earliest specimens ever found, he said.
Dr Ritchie hopes to raise funds to re-explore the fossil deposit and build an on-site museum for researchers and tourists.
A paleontologist and visiting fellow at the Australian National University, Gavin Young, believes the Australian Museum should take responsibility for all important fossil material found in NSW.
''In most other countries, and in some Australian states, regional museums remain sub- branches of the main museum,'' Dr Young said.
The Australian Museum's assistant director of research and collections, Brian Lassig, said the museum could not support all the country's approximately 3000 regional museums.
The museum had reviewed its priorities and moved away from paleontology and geosciences to focus on ''more topical issues'' such as biodiversity conservation, Dr Lassig said. ''What happened millions of years ago is interesting, but it's not going to influence the government's current thinking.''
But Dr Young said as well as being of great public interest, fossils were relevant to some of the globe's most pressing issues. ''At the time the Canowindra fish were alive, the Earth's atmosphere underwent some of the most dramatic changes in CO2 and oxygen levels in the history of the planet.''
Investigating the causes of this change was contributing to scientific predictions of climate change, he said.