Mandageria fairfaxi is reported by the state government to be "unique to NSW".

Deputy Premier and Member for Dubbo Troy Grant joined Minister for Industry, Resources and Energy Anthony Robert in presenting it to the public.

The 1.7 metre long fish fossil is reported to be 370 million years old and "one of the largest fossil finds in the world".

Found during a 1993 excavation at Canowindra, the fish fossil features a movable neck marking "a critical stage in vertebrate evolution".

Mandageria fairfaxi is named after a local creek and commemorates the contribution of publisher James Fairfax in supporting research into the fossil fish.

The Geological Survey of NSW undertook consultation with paleontological experts, cultural associations and institutions to determine a worthy state fossil emblem.

"This fossil builds on Canowindra's reputation as one of the best destinations for paleontology enthusiasts in the world," Mr Grant said.

"Canowindra is now home to the Age of Fishes Museum, close to where the fossils were originally found 60 years ago and has become a tourism beacon for the region.

"Visitors to this museum can follow in the footsteps of Sir David Attenborough and actually touch the real fossils of this fish."

The waratah remains the official NSW state floral emblem while the fish fossil joins four others.

NSW has a bird emblem in the kookaburra, an animal emblem in the platypus, a fish emblem in the blue groper and a gemstone emblem in the black opal.