The observant beachcomber on Phillip Island, in Victoria's Westernport Bay, will occasionally find a strange bivalved organism whose half-shells don't match - one half has an bulge like the crest on a helmet, which, in life, housed a unique feeding siphon called a lophophore.

This is no mollusc, but a brachiopod - a time traveller with a fossil record that extends deep into the Cambrian period, half a billion years ago. Brachiopods are old, and they have a tale to tell.

Brachiopod evolution is intimately linked to the Earth's own geological history over the past half billion years. Deakin University paleontologist and brachiopod expert Professor Neil Archbold has been using their fossils to reconstruct the breakup of the southern supercontinent of Gondwana, and determine the ultimate fate of its fragments, large and small, now scattered across more than half the globe.

Professor Archbold says brachiopods appear in the fossil record during the earliest Cambrian, and reach a peak of diversity in the Permian. During the Paleozoic, they were the most successful group of marine animals on the planet, with tens of thousands of species in 4500 genera.

But brachiopods are extremely common in the rocks of the Paleozoic era, which spans the rise of complex life forms in the Cambrian period 550 million years ago, to the end of the Permian period 250 million years ago.

This rich and diverse fossil record, says Professor Archbold, makes brachiopods wonderful markers in time and space - know your brachiopods, and you can determine the age of the sedimentary rocks in which they are found, and approximately where the rocks first formed from sea-floor sediments.

Brachiopod species are sensitive to changes in water temperature, so researchers can track ancient climatic trends that influenced their survival and distribution.

Because they have long been adapted to life in relatively shallow waters of coastlines and continental shelves, brachiopods are ideal subjects for reconstructing the outlines and locations of ancient land masses - the technique involves matching up similar fossils preserved in corresponding rock strata from different parts of the world.

Since the early 1980s, Professor Archbold and his colleagues have focused on identifying fragments of the southern supercontinent of Gondwana; their findings are helping minerals exploration companies to identify prospective mineralisation or oil deposits that formed in Gondwana and rafted to other parts of the globe as the supercontinent broke up.

The Deakin University researchers, with their Australian and international collaborators, are trying to reconstruct a picture of Gondwana as it existed during the Carboniferous and Permian periods.

Professor Archbold says the Permian period is of particular interest to Australian exploration companies, because it was when the major coal and gas deposits in the Sydney (NSW), Bowen (Queensland) and Collie (WA) basins, formed, along with some minor oil reserves.

Some 600-700 million years ago, the Earth entered a sustained cold climatic period unmatched until the beginning of the Permian period 300 million years ago. The Earth did not enter another comparable "icehouse" phase until the Pleistocene epoch 2 million years ago.

In the early Permian, half the world's continental areas were glaciated. By the late Permian, much of Europe lay beneath sand dunes or shallow, hypersaline seas that created the salt deposits found today beneath Germany and west of the Urals Mountains in Russia.

"But by the end of the Permian, the globe in most areas was absolutely torrid. Workers on the Permian are building up a picture of amazing global change during the period - we have a broad picture, and we are now trying to fill in some of the finer details.

"We feed out results into databases, such as those of the Australian Geological Survey Organisation, which then become available to industrial users."

One of the most common applications for the information is biostratigraphy - the use of fossils in identifying geological strata of a particular age.

"If a company is drilling an exploratory bore down to 3500 metres in search of gas, it can cost millions. But if, 50km to the east, there is a known gas-bearing horizon, it can save the company a great deal of money if knows what layers the gas deposit occurred in, so it doesn't drill past it.

Professor Archbold says that in Asia, entire regions with potentially new resources remain unexplored. "There are tremendous opportunities, and in Australia, we're brilliantly placed to collaborate with our Asian colleagues, and other European groups working in the region.

"That's not to forget the Indian subcontinent, where we have a major collaborative project with the Wadia Institute of Himalayan Geology to correlate the Indian and Australian Permian faunas.

"The whole of the Asian region is an exciting place to do geology. It's not like Europe, where geological research is highly evolved, or old European colonies like Canada, the US or Australia, which were substantially surveyed during the last century. It's a sort of Terra Nova, and the amount of new work being done is staggering."