The 2019 taxonomic review into the endangered grassland earless dragon revealed four genetically distinct subspecies - the Canberra, the Bathurst, the Victorian and the Monaro grassland earless dragon.
The first three have since been added to Australia's critically endangered list and the Monaro breed is now endangered, while some scientists believe the Victorian and Bathurst varieties to be extinct.
Museums Victoria lead curator for terrestrial vertebrates and study author Jane Melville isn't so sure.
"You need to be really conservative before anything's declared extinct," Dr Melville told AAP.
"These are secretive little animals, they live down in spider burrows, they're in dense grass - they're not that easy to see."
The Victorian grasslands earless dragon has not been spotted since 1969 and the Bathurst species was last seen in the 1990s.
Dr Melville said the subspecies had evolved in isolation as southeastern Australia's temperate grasslands gradually separated in the warming that followed the last glacial maximum about 20,000 years ago.
"But since European colonisation the grasslands have been basically removed for agriculture, urbanisation," Dr Melville told AAP.
It is estimated roughly 98 per cent of the temperate grasslands have been removed or degraded and the earless dragons, that grow to about 15cm in length, have been targets of introduced predators such as cats or foxes.
Australia is home to about 14 per cent of the world's reptile population, but they generally receive less conservation attention than birds and mammals, according to Charles Darwin University conservation science professor John Woinarski.
"As a community, we need to be less biased in our conceptions of nature and its values, and to recognise that all species have a right to exist," Prof Woinarski said in a statement.
"We must strive to prevent extinctions for any species, not merely the most charismatic.
"As a community, most of us recognise the plight of forest ecosystems, but our native grasslands also have suffered catastrophic losses and need investment in systematic and strategic conservation programs to recover."
Biodiversity Council lead councillor Brendan Wintle said it was devastating to see Australia's threatened species list continue to grow.
"There are now 1909 species on the national threatened species list," Professor Wintle told AAP.
"Current levels of investment in threatened species are grossly inadequate and will result in more endangered species and extinctions."
Prof Wintle said the World Economic Forum had ranked biodiversity loss as the third biggest threat faced by humanity in the next 10 years.
"The ongoing loss of Australia's biodiversity will have serious consequences for clean air, food and water, human health, Indigenous culture, our national identity and because roughly half of our economy ... relies on natural systems."
Australian Conservation Foundation campaigner Darcie Carruthers called on the federal government to strengthen environmental laws and boost threatened species recovery funding.
"If we value Australian wildlife, we must stop destroying their homes," Ms Carruthers said in a statement.
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