They can live for more than a century, seem to be able to keep menopause at bay and may hold the key to anti-ageing - if they don't die out first.
Researchers believe Australia's freshwater turtles, one of the most threatened groups of animals on the planet, could provide an insight into the biological process of growing old.
Freshwater turtle expert Dr Ricky Spencer of the University of Western Sydney says the oldest turtles produce the most eggs.
"There's no sign of menopause so they're defying the common-held view that cell death is inevitable," Dr Spencer said.
"These guys are either delaying that, or they don't expire like any other vertebrate."
But despite their natural longevity, Australia's population is "on the precipice of a major decline", he says.
Freshwater turtles, especially along the Murray River, are at greater risk of extinction than ever before.
Only 5 per cent of every clutch of eggs makes it to maturity, with introduced species like foxes enjoying an "all-you-can-eat buffet" during nesting season, Dr Spencer says.
The Murray River Shortneck is also falling prey to rising salinity levels in the water.
"Their only natural defence to salinity is to move along major highways, which follow the river," says Dr Spencer, adding that many are run over, such as the drought-affected Eastern Longneck, which travels great distances from waterhole to waterhole.
Freshwater turtles are crucial to river, creek, lake and pond ecosystems, eating pest fish such as the European carp, and vacuuming up algae and dead material.
However, while Australia's freshwater turtles are in peril, they haven't faced the same steep decline in numbers as other species around the world, Dr Spencer says.
He was commenting ahead of World Turtle Day today, which experts hope will draw attention to the plight of the reptiles.