Sunday , April 11 2021

Triassic reptile fossil discovered in the Antarctic



Representation of the artist Antarctanax shackleton (left handed). Along the stream, a large archosaur chops a couple of unbelievers.
Image: Adrienne Stroup, Camp Museum

The fossil remains of an ancient reptile of about 250 million years ago have been discovered in more unusual places: the Antarctic. The discovery shows how wildlife was recovered after the worst massive extinction in the history of our planet and how Antarctica lodged an ecosystem that is different from any other.

It goes without saying that paleontological work in Antarctica is very different from what is in other places. Unlike Alberta or Montana, for example, which has abundant rocky outcrops, Antarctica is covered by a massive ice sheet, which hides much of its palaeontological history. And it's not as if the Antarctic did not have stories to say a lot. Recently, in the last 30 to 35 million years, the continent froze. Before that, it was the home of a warm climate, leafy forests, streams rivers and a remarkable abundance of life.

To find fossilized traces of this forgotten life, either in Antarctica or elsewhere, scientists need to find rocks. Antarctica offers only two possibilities: islands along the coast and the Trans-Atlantic Central Mountains: a backbone of the mountains that cut a mountain range in the middle of the continent. The summits of these mountains cross the glaciers, create a rocky archipelago – and a place for palaeontologists to carry out a survey. It is here, in the Fremouw Formation of the transantharic mountains that Brandon Peecook, paleontologist of the Natural History Museum of the Field and principal author of the new study, discovered the Triassic reptile.

"Leaving the mountain, it was difficult to imagine that, indeed, the extraterrestrial Antarctica had been similar," Peecook told Gizmodo. "Looking around, I could not see any trace of macroscopic life for miles in all directions."

Prospecting Brandon Peecook in Antarctica.
Image: Roger Smith

In fact, Antarctica can be desolate and inhospitable today, but not always this way. Hundreds of millions of years ago, Fremouw Training was home to a lively, vibrant forest, of insects winged to herbivorous four-legged reptiles. The discovery of a previously unknown iguana reptile, called Antarctanax shackletoni, now adds to our knowledge the old ecological glory of the continent.

Antarctanax means "Antarctic king" i shackletoni It is a tip of the hat for the British polar explorer Ernest Shackleton. A. shackletoni It was a frog, sharing a common ancestor with dinosaurs and crocodiles and living during the Ancient Triassic Period about 250 million years ago. Now it is one of the first lizards that appear in the fossil record. The details of this discovery were published today in the Journal of Vertebrate Paleontology.

The partial fossil consists of excellent conserved vertebrae (including the neck and back), a partial skull, two feet, some ribs and a bone of the upper arm. It was discovered during an expedition to Fremouw Training during the 2010-2011 Antarctic summer. The analysis of these fossil bones (particularly of the skull) and fossils found next to it suggests that it was a carnivore of painted size, consisting of errors, amphibians and first protomates. Roger Smith from the University of Witwatersrand in South Africa and Christian Sidor from the University of Washington in Seattle attended Peecook with the analysis.

One side of the fossil, which shows the vertebrae and the arms of the arm.
Image: Brandon Peecook, Camp Museum

The Early Triassic is of great interest to the paleontologists, as it emerged after one of the worst episodes in Earth's history: the massive extinction of Permia, a time when extreme volcanism And prolonged it destroyed almost 90 percent of the life of our planet. It resulted in a green sweeper restart, setting the stage for survivors to be empowered. Among these survivors were arcosaurs, which took full advantage of them.

"A pattern that we see over and over again with massive disturbances as the final mass extinction of Permià is that some of the animals that managed to survive quickly filled empty voices," Peecook told Gizmodo. "The archosaurs are a great example: a group of animals that could do just about everything. This clade was only totally ballistic."

Opposite fossil face, showing several vertebrae, ribs and the right foot.
Image: Brandon Peecook, Camp Museum

In fact, archiotors, including dinosaurs, were among the great beneficiaries of this recovery period, experiencing enormous growth and diversity. Before mass extinction, these creatures were limited to the equatorial regions, but then they were "everywhere," according to Peecook, including, as we know now, the Antarctic. The continent was at home A. shackletoni about 10 million years before the appearance of true dinosaurs. In addition, Antarctica made dinosaurs hosts, but not until the Jurassic period.

This discovery also reveals the distinctive animals of the Antarctic. Since Antarctica and South Africa were physically connected at that time, paleontologists worked under the assumption that the two regions had much in common in terms of local wildlife. And since fossils are abundant in South Africa, paleontologists used this record to make inferences about the type of life that probably existed in Antarctica. But, as Peecook explained, this turns out to be an error; The Antarctic organized a different ecology to any other.

"We know very well the fossil record in South Africa, but in the Antarctic we have only discovered about 200 species," he said. "But we do not find these species anywhere else. Paleontologists have only gone to Antarctica several times, but every time they arrive they find new species and amazing new features: it's really exciting. The original argument you can Connecting these two environments is now inaccurate. Antarctic registry has many unique things that happen. "

That the Antarctic presents a unique set of species is not surprising. Like today, the continent was at a high altitude, with extended days in summer and long winter nights. Animals and plants had to adapt to survive, adopting new physical characteristics and survival strategies.

Mind makes us think of all the unknown and out of power fossils trapped under the Antarctic ice. As Peecook said, it has the paleontological record of what was once a truly strange environment.

[Journal of Vertebrate Paleontology]

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