Murdoch University dolphin researcher Simon Allen said photographs and biopsy samples from the miniature dolphins, the adults of which appear to measure just 1.5m, had confirmed the significance of the find.
A Woodside Petroleum spokesman said the Browse joint venture had spent more than $80 million to undertake environmental studies, including comprehensive studies of whales and other marine life.
"We are focused on designing our facilities and preparing for construction and operational activities that consider and manage the full range of environmental impacts," the spokesman said.
But Mr Allen said many dolphins had simply been listed as "unidentified" in Woodside's environmental assessment, and that no distinction was made between the normal spinner dolphin and this miniature dolphin.
More data is required to determine whether the miniature dolphin is related to the spinner dolphin, which measures about 2m and has been identified in the area, or the dwarf spinner dolphin, which is known to inhabit the Gulf of Thailand. Two tissue samples from the miniature dolphin have been analysed at a laboratory in Zurich and the test results confirmed the dolphin was a new discovery for the area.
Mr Allen and his colleagues are collecting more samples for further testing. He said it was possible the dolphin would be found to be a new species.
Despite dolphins being some of the most charismatic and popular animals on the planet, Mr Allen said very little was known of the different species across northern Australia. He added that the find reinforced how little was known about life in our