Australia’s burrowing echidna evolved from a water-dwelling ancestor in an “extremely rare” biological event, scientists said in a new study of the peculiar egg-laying mammals.
According to The Guardian, with powerful digging claws, protective spikes and highly sensitive beaks, echidnas are well suited to a life shuffling through the forest undergrowth.
But a team of Australian and international scientists believe many of the echidna’s unusual traits were first developed millions of years ago when its ancestors splashed through the water.
“We’re talking about a semiaquatic mammal that gave up the water for a terrestrial existence. While that would be an extremely rare event, we think that’s what happened with echidnas,” said Suzanne Hand, a palaeontologist from the University of New South Wales.
Echidnas and another Australian oddity – the semi-aquatic platypus – are believed to have evolved from a common ancestor called Kryoryctes cadburyi that lived in Australia more than 100m years ago.
Researchers studied the single known bone fragment left by this ancestor which was discovered among a trove of fossils at Dinosaur Cove in southern Australia 30 years ago.
Platypus bones were similar to this ancient ancestor, Hand said, with a thick and heavy structure that provided ballast for diving. Echidnas, by comparison, had very thin bone walls that made it easier to walk on land.
This indicated echidnas were descended from a water-dwelling ancestor but had evolved to live on land, the research found.
It was far more common for prehistoric mammals to go from land to water, Hand said, pointing towards seals, whales, dolphins and dugongs.
