Conrad Hoskin was drenched from an evening storm and forcing his body through a gully of ancient boulders when his torch hit something extraordinary.

The sheer size of the glowing, red eyes told him everything.

He knew he was staring at a creature entirely new to science, one that had evolved in isolation on a lush, granite outcrop on the Great Barrier Reef.

Dr Hoskin's discovery of the Scawfell Island leaf-tailed gecko is more than a year old but is only now being shared after a painstaking process to scientifically describe its peculiarities.

"It looks like a dragon with it's cute, beaky face and long, gangly legs," the James Cook University biologist says.

"I knew straight away that I had something, the minute I saw the eyeshine.

"Because it was bigger than other gecko options around there. It was one of those amazing experiences that as a kid you always dream about - finding something totally new."

It was in November 2021 that Dr Hoskin convinced the Queensland Parks and Wildlife Service to drop him off at uninhabited Scawfell Island, about 50km off Mackay.

A long and successful career of hunting for Australia's old rainforest fauna had left him with a deep suspicion the island, with its Jurassic-era granite, might be the perfect place of refuge for undiscovered species.

"Australia was once really quite rainforest-y, and over millions of years it has dried out. What we have now on the east coast is basically the persistence of really ancient rainforest lineages, when they can find a place of refuge," he says.

"I'm really interested in these lizards and frogs and over the years I've been targeting rocky, remote bits of rainforest because rock is amazing for buffering.

"You get cool, moist conditions deep down, and if you are going to survive through good and bad, over thousands and millions of years, you need a true refuge."

After landing on the island, he set off to explore one of its gullies, overhung with forest and full of boulders the size of cars and houses.

"As I climbed up, it just got better and better. Just on dark, we stopped in this fantastic place. It looked like a movie set with deep boulders, big fig trees and ferns all over the rocks.

"It bucketed down that night so it was quite treacherous but when the rain eased we worked our way through the rocks and started to see the eyeshine."

The gecko that now shares the island's name is on the larger end of the scale when it comes to Australian species.

Like other leaf-tailed geckos it has a distinctive back end, but this one has a fringe of spines around the tail.

It also has expert hiding skills thanks to a unique colour pattern, which is good considering it's rather dopey and slow.

"Because they rely on camouflage, they just sit there. They're like, 'Oh no, don't see me, don't see me'. They're really slow, almost like a chameleon or something."

It's hard to know how big the population is but there are at least 30 individuals. More work is needed to determine if the species is endangered or not.

Meanwhile, Dr Hoskin hasn't given up on finding more new species to add to the 35 he's been involved in naming so far.

"There's not a lot of these bigger boulder-y, rainforest-y islands out there. And Australia is a pretty well explored place now. But I do think there's going to be a couple more of these hidden treasures."