On a break from his two-week speaking tour around the country, Sir David was taken to a site in NSW's central west where hundreds of ancient fish perished at the bottom of a small lake 360 million years ago.

Arguably one of the country's most impressive fossil deposits, the site reflects a time when fish ruled the world and animals were on the verge of walking on land.

Today, evidence of this event can be seen on several large rock slabs on display at Canowindra's Age of Fishes Museum.

''When you look at one of these slabs you can see it is extraordinary,'' said Sir David.

''What you have here is dozens and, if the rock was big enough, hundreds of these things piled one on top of another.''

The intrepid traveller, who turned 87 in May, was invited to visit the rare fossil deposit by Australian palaeontologist Alex Ritchie, a world authority on early fishes and former senior researcher at the Australian Museum.

Dr Ritchie led the first, and only, excavation of the road side site just outside Canowindra exactly 20 years ago this week.

Several leading international palaeontologists believe the site may contain some of the earliest evidence of tetrapods, the first animals to walk on land.

Sir David said the high quality exhibits at the small Age of Fishes Museum, run by the Cabonne shire council, were a credit to the local community.

''But the find is world class and it deserves even more than it has got here,'' he said. ''It would be nice to think that the state or the nation should support such a thing.''

While it was typical for state museums to support important fossil sites, the Australian Museum said earlier this year it could not support all of the country's regional museums or store all of their material.

The assistant director of research and collections, Brian Lassig, said the museum had reviewed its priorities and was more focused on issues such as biodiversity conservation.

Dr Ritchie said no other fossil fish site of this age in the world compared to Canowindra.

''I reckon there's another 5000 to 10,000, possibly 20,000, more fish under there. It's just waiting to be dug up and turned into a major tourist, educational and research facility. The Australian Museum have pulled out and washed their hands of Canowindra and that's a tragedy.''

The fossil specimens Dr Ritchie discovered belong to the area's regional council, but they could not afford appropriate storage space for all the specimens, which meant most were housed in the dilapidated basement of the town's grandstand.

Dr Lassig said the Australian Museum was working with the shire council to secure funding to improve the storage.