At a maximum length of 23 centimetres and weighing just 16 grams, the world's smallest species of goanna has been discovered in the Kimberley.

The Dampier Peninsula goanna, or Varanus sparnus, has been described as an evolutionary marvel.

Scientists believe the species of little lizard has remained unchanged for over 6 million years.

"We estimate from the genetic information [that the species] diverged roughly about the same time that chimpanzees diverged from human beings," said Dr Paul Doughty from the WA Museum.

With huge variation in body mass, the goanna family also includes komodo dragons and monitor lizards which dwarf new species.

"The biggest mass of the largest [Dampier Peninsula goanna] was 16 grams, with a length of about 23 centimetres, whereas a komodo dragon is about 80 kilos at least, and over three metres long," Dr Doughty said.

"So it's all in the same group, but different scale."

Believed to live exclusively north of Broome and Derby, the lizard was discovered by environmental consultants surveying the area.

It adds to an impressive list of Australian reptiles.

"We've just broken 1,000 species of reptiles in Australia, which is a 10th of the world's diversity," Dr Doughty said.

One of the goannas, nicknamed Pokey, is living in captivity at the WA Museum.

Three others, which have died, have been preserved in jars for classification and recording purposes.