A South Australian family has discovered a group of ancient bones in north-west Queensland on their first attempt at fossil hunting.

Several flipper bones and vertebrae of an ichthyosaur - an extinct marine reptile - were unearthed last week at Richmond's Kronosaurus Korner museum.

Family patriarch Paul Gardner-Stephen said it was the family's first punt at fossil hunting.

"It's really exciting ... the prospect that something we found on holiday might be shown in the museum up there," Mr Gardner-Stephen said.

"In a matter of a few hours of digging with some simple hand tools. We had found a really large marine reptile and so I think the prospects are great for anyone else who's interested in this kind of thing to go up there and see what they can discover."

Mr Gardner-Stephen said it was an amazing moment, especially for his two children, Isabel and Caleb.

"The kids were really excited, our seven-year-old daughter in particular," he said.

"I think she has some understanding of the magnitude really of what we've just done as a family.

"She was really excited and I think she'll be looking forward to showing some of the bones to her class once she gets back home to Adelaide.

"Our son is four-and-a-half. He was having fun, but I think it'll be a few years before he realises [the significance].

"My wife and I sort of remember sitting there, looking at each other, and talking about how surreal it was digging up what is a really massive animal."

The family dug up several flipper bones and vertebrae of an ichthyosaur - an extinct marine animal - during a fossil dig in Richmond, north-west Queensland. ( Audience submitted: Paul Gardner-Stephen )

Kronosaurus Korner curator Dr Tim Holland said the 100 million-year-old bones were uncovered by the Gardner-Stephen family over a number of days.

"The father lifted up slabs of rock and found the bones from the flippers of an ichthyosaur," Dr Holland said.

"They stayed out the next day and found more flipper bones, and also vertebrae of the same ichthyosaur which were roughly about the size of a hockey puck.

"The following day we all went out there together.

"They'd uncovered the back part of the skull of this creature as well."

This past week's discovery follows on from a similar discovery in March when tiny bones of fossil fish, shark teeth and turtle bones were uncovered after 200 millimetres of rain flooded parts of a fossil hunting site 12 kilometres north of Richmond just three months prior.

Dr Holland said the most recent findings are revealing new information about the species.

"In the place that they found it we actually have three other ichthyosaurs that have been probably found over a period of four years, so we're thinking that this environment may have been a spot where these ichthyosaurs could have stranded and have died together," he said.

"There was also, in that group of four, a baby ichthyosaur found so we're thinking that the inland sea might have been a place where the ichthyosaurs were breeding and possibly raising their young."