Difficulty: Challenger (Level 2)
A team of Australian and international scientists believe many of the echidna’s unusual traits were developed millions of years ago when its ancestors lived in the water.
This is based on the results of a study announced in April.
Echidnas and the semi-aquatic platypus are believed to have evolved from a common ancestor called Kryoryctes cadburyi that lived in Australia more than 100 million years ago.
Echidnas and platypuses are monotremes, a rare group of mammals that lay eggs instead of live young.
Palaeontologist Suzanne Hand said that echidnas had fragile bone walls that made it easier to walk on land. Hand is a palaeontologist at the University of New South Wales. This shows that echidnas came from an ancestor living in water but evolved to live on land.
It was far more common for prehistoric mammals to go from land to water, Hand said, pointing towards seals, whales, dolphins and dugongs.
Echidnas have hind feet that point backwards. That helped them move lots of soil when burrowing. Hand said that the echidna’s ancestor might have first used these feet like rudders to move through fast water.
Echidnas also have a “diving reflex” when they go underwater. This tells their body to conserve oxygen to help them hold their breath for longer.
Agence France-Presse
