A microscopic collection of worms and mites could play havoc with a coal seam gas project proposed by Santos in a state forest in New South Wales.
The ancient, subterranean creatures that live deep in an underground aquifer are only 1mm long and thinner than a human hair.
They are known as stygofauna and they play an important role in filtering and determining the quality of groundwater.
The ABC reports new evidence about the stygofauna is contained in one of 1800 submissions to the federal government opposing plans by Santos to drill 18 gas wells in the Pilliga State Forest near Narrabri.
Santos has estimated the project could supply 25% of the state's gas needs.
The government now has to determine if the company can go ahead with the drilling.
Hydro-biologist Dr Peter Serov, who found the two new species of stygofauna, said the creatures are extremely sensitive to changes in water quality.
"There needs to be a lot more rigorous sampling and monitoring of both water chemistry and biodiversity across the region to determine what the ultimate ranges of these species are and what their environmental requirements are at this point in time," he said.
Dr Serov said stygofauna are highly specialised organisms that have been around for hundreds of millions of years.
"They are a group that have adapted over millions of years to occupy a very, very specialised niche," he said.
But Santos groundwater expert Peter Hancock wants to know just where the tiny animals were found.
Dr Hancock said they may not exist in the deep aquifers that coal seam gas wells drill to.
"The deeper coal seam aquifers are unlikely to have stygofauna in them. It's the shallow alluvial aquifers that are most likely to have them," he said.
Independent MP Tony Windsor says the scientific process must go ahead before the coal seam gas company moves in.
"We don't fully understand the scientific nature of some of these groundwater systems and until we do at a scientific level, I think the political process should step back and the industry process should step back until we get the science right and then make the decision," he said.