University of Wollongong palaeontologist Dr Gert van den Bergh and archaeologist Professor Mike Morwood stumbled on an almost complete ancient elephant skeleton in April.

"It's very rare," Dr van den Bergh said.

"It is one of the most complete elephant skeletons ever recovered in Indonesia."

Along with a team from the Geological Survey Institute, Dr van den Bergh and Prof Morwood are cleaning and preserving the bones, which will be pieced together for a museum display later this year.

They found the fossils in a quarry near the Solo River in east Java, a place abandoned after two people died in a landslide there several years ago.

The extinct elephant was buried under 3m of sediments and sand, with some bones and flesh still intact.

"This is what makes it so exceptional - we can get a good idea of what the species looked like," Dr van den Bergh said.

Dr van den Bergh suspects the elephant died after getting stuck in quicksand.

"We know from the structure of layers found near the elephant that it was a river bed," he said.

"Maybe the elephant entered the river to cross it, sand collapsed under its feet and it couldn't get out.

"Then the next flood completely covered the elephant, and maybe that's the reason it's been preserved so well."

The palaeontologist had been travelling between the university and Indonesia since the discovery and was excited to be able to excavate the skull, the main piece in the puzzle.

But as it has not been cleaned yet, Dr van den Bergh said it was hard to determine the species.

"But we know it was very big; bigger than modern elephants you'd find in Asia."

The team is working on cleaning and preserving the fossils before putting it back together and handing it over to the Geology Museum in Bandung for permanent display.

The team would reconstruct some pieces for the feature, such as the tusks.