The rare species of ommatid beetle was older than Australia, originating when the earth's continents formed one vast landmass, entomologist John Lawrence told reporters.

Two specimens, which mainly populated South America, North America, Europe and Asia 145 to 210 million years ago, were unearthed by scientists in 1991 and 1995 at different reserves in the state's Mallee region, north-east of Adelaide.

Lawrence said the importance of the findings went unnoticed for several years until he recently checked the survey material.

``The peculiar look of the animal caught my eye straight away,'' he said.

``The unique combination of spines, scales and lack of wings. At first I was puzzled, then I realised it was an ommatid, a member of a family of beetles which dates back to the Jurassic.''

While the species remained rare, the discovery of twospecimens suggested there would also be others, with a population of thousands possible.

``We know next to nothing about them,'' he said, adding that the beetles spent most of their time underground.

Its antiquity was evident in the presence of certain body parts which, in modern beetles, had either fused with other body parts or disappeared altogether.

Among those were the stout spikes which protruded from its body scales, contrasting markedly with other, smoother, members of the omma family.

``Generally speaking, the ommatids are a group that has always been able to survive in marginal habitats, in the drier parts of the continent,'' Lawrence said.

``They bore into rotten wood so they are probably important to the process of breaking down old wood and maintaining the fertility of the soil.''