Australia’s echidna, an atypical mammal that lays eggs, has experienced an “extremely rare” biological evolution from an ancestor living in water, scientists indicate in a new study published on Tuesday.
Equipped with powerful claws, spines and very sensitive beaks, the echidiaries, long of several tens of centimeters, are well adapted to a life of fouisseurs in the undergrowth. But a team of Australian and international scientists thinks that many of the unusual characteristics of the Echidné developed millions of years ago when its ancestors lived in the water.
The same ancestor as the ornithorynque
“It is a semi-aquatic mammal that abandoned water for a terrestrial existence,” explains paleontologist Suzanne Hand, from the University of South Wales. “This is an extremely rare event, but we believe that this is what happened in the echidiaries,” she said, according to the study published in the journal “Proceedings of the National Academy of Sciences (PNAS)”, official review of the National Academy of Sciences in the United States.
The echidins and another Australian species, the semi-aquatic ornithorynque, would have evolved from a common ancestor called Kryoryctes Cadburyi who lived in Australia over 100 million years ago. The researchers studied the only known bone fragment left by this ancestor, discovered among fossils in Dinosaur Cove, in the south of Australia, about thirty years ago.
The bones of the ornithorynque were similar to those of this ancestor, explained Ms. Hand, with a thick and heavy structure which served as a ballast for diving. In comparison, the bone walls of the echidnates were very fine, allowing them to walk more easily on firm land.
This indicates that the echids descend from an ancestor living in water, but who has evolved to live on firm land, according to the results of this study.
The passage from the earth to the water, more common
It was much more common for prehistoric mammals to switch from earth to water, underlined Ms. Hand, citing the case of seals, whales, dolphins and dugongs.
The researchers note that these results seem to be corroborated by several other characteristics of the echidna. The posterior legs of the animal turned backwards which help them to move the earth mounds were able to be developed as rudder first to help the ancestor of the echidna to navigate in quick rivers, according to Ms. Hand.
The animal multiplies the oddities. Thus, he has a four -headed penis of which only two swell at the same time. He is also able to make bubbles at the end of his trunk, which he bursts to refresh himself.
Echidans and ornithorynques are monotrma, a rare group of mammals that lay eggs but also breastfeed their young.
“We hope to discover other ancestral monotrums that will help us discover the history of this group of fascinating mammals,” said Michael Archer, co -author of the study.
