A chance discovery of an echidna skin and skull in London's Natural History Museum suggests an echidna species, thought to have become extinct in Australia around 10,000 years ago, may be still living in the remote Kimberley region.

Conventional understanding suggests Australia is home to just one species of echidna, which shares the unusual habit of being a mammal that lays an egg with its monotreme relative the platypus.

But the old skin found in the museum in London has been confirmed as being that of a much larger western long-beaked echidna, collected in the west Kimberley in 1901.

The sparsely-populated rugged Kimberley region, with a total area almost as big as Spain, is exactly the type of place where such an unusual animal could go unnoticed, even in the 21st century, according to Professor David Watson from Charles Sturt University.

"Nobody's actually had a good look," Dr Watson said.

"When this specimen was unearthed, collected at the turn of the last century, it got a lot of us thinking, 'Holy-moly that's remarkable. Could it still be there?'"

Natural History Museum long-beaked echidna specimen collected from Australia in 1901 ( Supplied: Natural History Museum )

While finding a large mammal that was thought to be extinct in Australia may seem unlikely, the recent discovery of the once thought to be extinct night parrot in the Kimberley is one example Dr Watson points to.

"That sort of example is really inspiring, and the other one that springs to mind is the Wollemi pine, a great big rainforest tree on the doorstep of Australia's biggest city," he said.

"It's equally improbably and unlikely, and yet it's happened."

The power of poo

A search for the western long-beaked echidna is planned for later this year, and a specially-honed tool gives Dr Watson confidence he may find the animal that has been overlooked since 1901.

Three dogs are being trained to seek out echidna poo.

If the long-beaked echidna still exists in Australia, it is obviously hard to find.

But even elusive animals have to poo, and with DNA technology, a single poo could confirm the existence of Australia's second echidna species.

An added advantage for Dr Watson's echidna poo-seeking dogs is that the western long-beaked echidna still exists in parts of New Guinea, and one lives in captivity at Sydney's Taronga Zoo.

"They've got the only captive long-beaked echidna in Australia, and we've secured the rights to its droppings," he said.

The long-beaked echidna droppings will be used to train the dogs to sniff out the poo of what is a very different kind of animal.

"It's a much bigger, more heavily built animal, it's completely nocturnal," Dr Watson said.

"It's furrier, it is spikey but the spines don't emerge from the fur as much so it looks woollier, it's got a much longer snout, and it is a rainforest specialist."

If signs of a new species of echidna for Australia are found, more specialised studies would follow to understand how these mysterious animals may have gone unnoticed for so long.

"Even where they live and where you can see them now in New Guinea, they're really poorly known," Dr Watson said.

"There's very few studies that have been done on them. There's a couple of zoos that have tried keeping them, but they are enigmas."