Footprints found in Australia change theories on the origin of reptiles

Distinct footprints with claws found in a 356 million year old rock slab from Australia suggest that reptile relatives emerged between 35 million and 40 million years earlier than previously believed.

The footprints also set back the source of the amniotas, a group that includes reptiles, birds and mammals, and provides new evidence on how animals have made the transition to live exclusively in the seas to live on land.

Amniota represent a crucial part of the transition from aquatic to earthly life, as they were the only Tetrapods, or creatures of four members, which evolved to reproduce on land.

Previously, older body fossils and footprints associated with amniota dated 318 million years in Canada. But the new discoveries, published on May 14 in the magazine NatureThey challenge these longtime assumptions and indicate that the transformation of the Tetrapods living in water to live on land probably occurred much faster than scientists imagined.

“I am astonished,” says study coauthor Per Erik Ahlberg, professor of evolutionary biology and development at the University of Uppsala, Sweden, in a statement. “A single slab with footprints, which a person can carry, in doubt everything we thought we know about when modern tetrapods evolved.”

The site of the discovery indicates that Australia, which was once a central part of the former southern supercontinent Gondwana – which also included the current Africa, South America, Arabia, Madagascar, Antarctic and India – can be the ideal place to look for more fossils of amniotas and reptiles – and where they originated, according to the study’s authors.

Rewriting evolutionary history

The rock slab, found by amateur paleontologists and co -authors of Craig Eury and John Eason study in Victoria’s Snowy Plains formation in Australia, seems to show two sets of footballs of the same animal representing the older claws ever discovered.

The shape of the feet is similar to that of a modern water monitor and, although the exact size of the animal is unknown, it may look like a small creature similar to a Goaanna, about 80 centimeters long, according to the main author of the study, John Long, strategic teacher of paleontology at Flinders University. Asian water monitors are large native lizards of southern and southeastern Asia, while Goaannas are large common lizards in Australia.

Curved claws, a specific key characteristic of reptiles, may have allowed this primitive tetrapod to crash and cast trees.

The animal that made the footprints is the oldest known reptile and also the oldest known amniota, according to Ahlberg. And it is helping scientists decipher as Tetrapods have evolved.

“Our new discovery implies that the two main evolutionary strains that led to modern tetrapods – one, the line of modern amphibians, and another, the line that leads to reptiles, mammals and poultry – diverged from each other long before, probably still in the Devonian period, about 380 million years ago,” says Long.

Prior to this discovery, it was believed that the Devonian period was a time of fish-like fish and “fish” tiktaalik, which exhibited fish and first tetrapod characteristics and began exploring coastal lines in a limited way.

But the new study reveals a diversity of large and small tetrapods, some aquatic and some largely or totally terrestrial, which probably lived at the same time.

“One of the implications of our research is that the diversity of Tetrapods at this time was greater and included more advanced forms than thought,” Ahlberg wrote in an email.

It is crucial to understand when life has made the transition from totally aquatic to terrestrial because it represents one of the greatest milestones in the evolution of life, according to Long. This transition showed that animals were no longer dependent on living in the water or near it.

The transition occurred in part because the amniota evolved to reproduce with hard shell eggs instead of soft shell.

“The migration of vertebrates to the earth was an important part, and within that a fundamental step was the evolution of the amniotic egg in the immediate ancestors of reptiles and mammals,” says Ahlberg. “Therefore, these events form a key episode in both our own ancestry and in the history of the planet.”

The new study pushes the source of amniotas much farther back in the carboniferous period, from 299 million to 359 million years ago, allowing a much longer period for the diversification of the first reptiles, according to Stuart Sumida, president of the Vertebrate Paleontology Society and professor of biology at California State University in San Bernardino. Sumida, who wrote a complementary article to be published along with the study, did not participate in the new research.

The search for the origin of the amniotas

Long studies fossils of old fish in the Mansfield district, where the slab has been found since 1980.

“The Mansfield region produced many famous fossils, starting with spectacular fossil fish found 120 years ago, and old sharks. But the ‘holy Grail’ we always sought was evidence of terrestrial animals, or tetrapods, like the first amphibians. Many sought for such traces, but never found them – until this slab came to our laboratory to be studied, ”he says.

Mansfield district fossils have already helped to clarify how sexual organs may have first evolved into armored old fish.

Now the researchers want to know that other beings lived in Gondwana along with the old reptile they found.

The findings inspired the researchers to broaden the pursuit of fossils of the first amniota and their close relatives to the continents of the southern hemisphere, according to disappeared.

“Most of the skeletal fossil discoveries of the early amniota are known from continents from the northern components of pangeia,” says disappeared in an email. “These findings suggested that the source of amniota could be in these regions. Now it seems to me to be clear that we need to expand our search for lower coalfish in Australia, South America and Africa.”

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This content was originally published in footprints found in Australia change theories about the origin of reptiles on the CNN Brazil website.

Source: CNN Brasil