The story of the Canowindra fish bed has the sort of serendipity about it that often marks great discoveries. In 1956, trucks travelling the unsealed Gooloogong road were grounding on a protruding hummock. The Carbonne Shire despatched bulldozer driver Charlie Stevens to remove the obstacle. Carefully he levered up the slab and left it propped up by the roadside.

A few months later the rains had washed it clean. Bill Simpson was droving cattle along the road and saw the monolith consisted of a dense throng of fishes of peculiar shape and variety, 114 victims of some prehistoric holocaust. The slab was duly reported to the Australian Museum, where for more than a quarter of a century it held pride of place in the fossil gallery.

Intrigued, (Dr.Alex) Ritchie visited the site in 1992 and a quick survey persuaded him far more lay beneath the strata, but his crowbar and hammer made little impression on the sandstone. A year later he returned with a more suitable implement, a 22-tonne excavator loaned by the shire and a team of enthusiastic volunteers mustered from the local community.

What surfaced took their breath away. Impressed into the living rock was the story of a quintessentially Australian tragedy - thousands upon thousands of fish trapped in the mud of a drying lake bed under a baking Devonian sun, more than 350 million years before the first human footprint marked the earth.

Gently the drought shrouded its victims in a layer of dust and, when the lake refilled, the forms of the fish were frozen for eternity in their rocky tomb.