Fossil find rewrites evolutionary history of platypuses and echidnas
The latest research suggests that echidnas and platypuses originate from an aquatic ancestor, rather than a terrestrial one, as was previously thought. New insights have emerged from the analysis of a fossil dated to 108 million years ago, discovered in Australia.
Recent studies propose that echidnas and platypuses may descend from an aquatic ancestor. Evidence for their origin comes from a 108-million-year-old fossil unearthed at Dinosaur Cove in Australia. These distinctive animals, referred to as monotremes, are categorised as egg-laying mammals and may have evolved from an aquatic or semi-aquatic environment. Professor Suzanne Hand from UNSW highlights that while there are numerous instances of mammals evolving from land to water, the opposite phenomenon is exceedingly rare.
Platypuses and echidnas are the only extant mammals today that lay eggs. Platypuses, found in Australia and Tasmania, are noted for their distinctive duck-like beak, while echidnas, covered in spines, resemble hedgehogs. After laying eggs, the female incubates them in a special pouch or depression on her belly. Once hatched, the young feed on milk that seeps through pores in the skin.
Groundbreaking research by Australian scientists
Research carried out by the University of New South Wales (UNSW) challenges earlier theories. As reported by the Science Alert portal, the analysis of the humerus bone, found by a team from Museums Victoria, reveals similarities to semi-aquatic animals like the platypus.
Is Kryoryctes cadburyi the key to understanding the past?
The humerus bone belonging to the extinct species Kryoryctes cadburyi was discovered in the 1990s. This bone is unique as it is the only one found of this species. Its internal structure resembles the bones of platypuses, suggesting that the ancestors of echidnas might have been semi-aquatic.
UNSW scientists employed advanced scanning techniques to examine the bone's internal structure. They found it to be more similar to platypuses than to echidnas, suggesting that echidnas' ancestors might have adapted to life on land, losing the dense bones typical of aquatic creatures.
Searching for further evidence
Professor Michael Archer from UNSW stresses that studies on opalised fossils from Lightning Ridge could provide additional information about the early history of monotremes. Scientists hope to uncover more ancestors that could help solve this intriguing evolutionary puzzle.
