The story of two of the Strange animals on the planet It became even more curious, thanks to the tracks revealed by a lonely fossil that, according to scientists, represents an ancestor long extinct. The new research can know what you know About the evolution of the most primitive mammals that still exist.
ORNITORRINCO and EQUIDNA, found in Australia and New Guinea, are called monotremado – a unique group for including the only mammals that lay eggs.
The organicorrinco, an amphibious animal, has spouts and feet in a duck, as well as a tail similar to that of a beaver. This small animal spends much of the time hunting food in the water.
Equidna-properly known as an anteater-lives exclusively on land, is covered with pointed thorns and has back-back paws, which helps her to turn the earth while digging. Neither animal has teeth and, although both produce milk, do so through the skin, as they have no nipples – the puppies, called puggleslick the milk directly from the skin.
“These little creatures have plenty of plenty of,” said Dr. Guillermo W. Rougier, professor at the Department of Anatomical Sciences and Neurobiology at the University of Louisville, Kentucky, who studies the evolution of early mammals.
“They are one of the defining groups of mammals,” said Rougier. “The typical dinosaur mammal probably shared much more biological characteristics with a monotremal than with a horse, a dog, a cat or with us.” Therefore, he added, the Monotremados offer a window to the origins of mammals on the earth.
Exploring the interior of an ancient fossil
A new study published on Monday (28) in Proceedings of the National Academy of Sciences further opens this window. The research, led by paleontologist Suzanne Hand, emeritus professor at the School of Biological Sciences, Earth and Environment at the University of New South Wales, Australia, reveals the internal structure of the only known fossil of the monotreed ancestor Kryoryctes cadburyiwho lived more than 100 million years ago.
THE fossil – a humerus, or bone of the upper arm – was discovered in 1993 in the Dinosaur Cove, in southeastern Australia. On the outside, the copy looked more like a bone of an terrestrial equidna than with that of a water ornitorinator. But when the researchers looked inside, they saw something different.
“Using advanced 3D image techniques, we were able to reveal previously invisible characteristics of this old bone, and they told a very unexpected story,” said study co -author, Dr. Laura Wilson, senior professor at the Earth and Environment School of the University.
The team found that internally the fossil had characteristics of the semiaquatic ornitorrym: a thicker bone wall and a smaller central cavity. Together, these characteristics make bones heavier – something useful for aquatic animals as it helps reduce floatability, facilitating dive to seek food. In contrast, the equids, which live exclusively on land, have much thinner and lighter bones.
The discovery supports the popular hypothesis – but until then not proven – that Kryoryctes It would be a common ancestor of both the organ and equidna, and that, at the time of dinosaurs, this animal may have lived at least partially in aquatic environments.
“Our studies indicate that the amphibious lifestyle of the modern ornitorrencine originates from at least 100 million years ago,” said Suzanne Hand, “and that the equidnas have returned to a totally terrestrial lifestyle much later.”
The evolution of organ and equidnas tells the history of mammals
There are well-known examples of animals that have evolved from earth to water-for example, dolphins and whales are believed to have evolved from land animals and share lineage with hippos. But there are few documented examples of evolution in the opposite direction, from water to earth. This transition requires “substantial changes in the musculoskeletal system,” Wilson explained, including a new limb positioning to land and lighter bones, to make the movements less expensive in terms of energy.
A transition from water to earth can explain the feet turned back to the equidna – a strange feature that, according to Hand, may have been inherited from a water ancestor who wore the rear paws like lemes on swimming.
“I think they proved very elegantly the hypothesis that these animals adapted to a semiaquatic life very early,” said Rougier, who did not participate in the study, although he had contact with the authors during the research.
The primitive history of these unusual animals, according to him, is “truly crucial” to understand how mammals – including humans – have emerged.
“Monotremados are living relics of an extremely remote past. You and an ornitorrinco have probably had a last common ancestor for over 180 million years,” he said. “There is no way to predict the biology of this common ancestor without animals such as monotremado.”
This content was originally published in a new study reveals the evolution of the strangest animals on Earth; Meet on the CNN Brazil website.
Source: CNN Brasil
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