It was a time of catastrophic change. Most life on Earth had been wiped out, global temperatures had risen dramatically, and the weather was raging in extremes. That something survived in this harsh environment is remarkable, and yet some plants and animals persisted. One of these survivors was Lystrosaurusa four-legged herbivore with a beaked snout and two sharp tusk-like teeth. And now, more than 250 million years later, paleontologists have discovered two fossils of these little animals complete with mummified skin.
This exciting discovery is described in a paper Posted in Paleogeography, Paleoclimatology, Paleoecology. Jhim two Lystrosaurus fossils are among the 170 fossils from the Karoo Basin in South Africa studied in this article. The Karoo is one of the few places in the world that records the boundary separating the Permian and Triassic periods, a boundary that includes the Late Permian Extinction Event (EPME) that killed off most life marine and terrestrial around 252 million years ago.
Lead author Roger Smith has worked there for 47 years. He is an eminent professor at Institute for Evolutionary Studies from the University of the Witwatersrand and Emeritus Research Associate at South African Iziko Museum in Cape Town. He and his colleagues Jennifer Botha and Pia Viglietti studied a known outcrop Lystrosaurus hotspot, having produced more than 500 fossils. But for this article, they focused on 170 fossils of tetrapods – a term referring to four-legged vertebrates – all from a time known as the Age of India, which covers the million years after the EPME. Among the many fossils studied in this outcrop, clusters of four to eight Lystrosaurus fossils have been found close together, their bodies spread apart, two of them preserving mummified skin.
This skin, Smith explained in a video callalmost matched what he predicted: the animal had no hair, as evidenced by the absence of hair follicles, but it was not scaly, That is. Noting that scales often don’t keep, he compared it to elephant skin: tough but with dimples. “The idea that it was like a transitional fossil – between scaly and true hairy – is almost confirmed by the texture of this skin,” he said.
Juan Carlos Cisneros is a paleontologist at the Federal University of Piauí in Brazil. Although not involved in this research, he too has worked in the Karoo basin and previously collaborated with Smith. “It’s the closest thing to a photograph of them at that time,” he said, comparing the mummified fossils to “a time capsule.”
“We are generally satisfied with having nice teeth, nice bones, and every once in a while we find a complete skeleton. But no one else finds mummified skin. Not at this age, of course! We’re talking about things older than dinosaurs,” he enthused. “Nobody finds this kind of beautiful preservation, so detailed, at that time.”
What provides exquisite insight into animals over 250 million years old is also an indication that they met a horrific end. Examination of the bone microstructure of two of the fossils suggests that they were young. The authors believe that the position and age at which these dead animals are clues that they have collapsed near a dried up water source. They cite examples of today’s young elephants in similar drought circumstances starving in a splayed “sudden death posture” and whose skin, among other things, dries out rapidly and also mummifies.
These groups of fossils, together with the others studied in this outcrop, indicate that herds of young Lystrosaurus died as a direct result of the drought. Substantial evidence of drought is found in the sedimentary layers of the Karoo basin, in geochemical isotopic analysis, and in these and other layers fossils described in many articles. This is why it is surprising that Smith asserts that “even if the world had been devastated, the resulting ecosystem was still fully functioning”.
In other words, the planet may have been completely transformed – and into a hostile planet to boot – but life, paraphrasing the words of a great movie, still found a way.
Evidence suggests that land animals in the Karoo at this time grew rapidly, matured earlier, lived short lives, and were generally smaller. Species of Lystrosaurus during the Permian, for example, were larger than those found in the Triassicbut it is also important to note that all Lystrosaurus the fossils still discovered from the Triassic are juveniles and subadults.
Cisneros compared the size of Lystrosaurus after the EPME to that of a small pig and said that it was “the largest land animal of that time. Everything that survived the mass extinction was small.
“Before extinction,” Smith confirmed, “being big and heavy and a ruminant was fashionable. But after that it wasn’t successful anymore.
Digging underground is one of behaviours believed to have helped Lystrosaurus survive the extinction and the extreme heat that followed this event. But that’s not all, and some of the other survival strategies involve, if not interspecific cooperation, then at least interspecific tolerance. In one example, the authors point to the fossils of two Lystrosaurus species that died together, indicating that these species may have foraged together, rather than arguing.
Sharing shelter with other contemporary species was another example. In three cases, several species including Lystrosaurus were found together in association with casts of long tube burrows, strongly indicating that these animals sheltered and died together.
Within these former shared shelters, three of the species were four-legged reptiles (Thrinaxodon, Galesaurus and Lystrosaurus); one of them (Prolacert) was a four-legged archosauromorph, a line that would eventually give rise to crocodiles and dinosaurs.
Smith said he and his colleagues are finding more evidence “now that these dinosaur ancestors could not only live there, but were able to branch out and become the dominant animals in the Triassic. ‘This,’ he concluded, “is the beginning of the rise of the dinosaur.”
While the causes of the EPME continue to be debated, the authors draw on their work in the Karoo Basin to support the hyperthermal cause of the extinction, meaning Earth was catastrophically impacted by an eruption volcanic in the Siberian traps around. 252 million years ago, an event that changed the climate through the volcanic emission of greenhouse gases and acidic particles. This had devastating consequences, including “vegetation death and drought (aridity with shorter, unpredictable periods of rain) on land,” Smith explained, as well as “deoxygenation and acidification of the oceans.”
“We are now treating this as Pangea-wide hyperthermia,” Smith added, referring to the only continent that comprised land on Earth at that time. “Therefore, Pangea-wide drought episodes would be expected.”
This article, he noted, is part of a larger project he and his colleagues have been working on in the Karoo Basin: just one of many articles that preceded it and more exciting articles to come. .
“Much remains to be resolved,” Smith admitted, adding that he believes that when he and his colleagues complete their research on the Karoo Permo-Triassic Boundary (PTB) interval, he believes they will be “recognized as the type locality”. for the Late Permian Earth Extinction Event.
“The Karoo has the best and most complete fossil record of these Permian Triassic tetrapods,” Cisneros agreed. “If there’s one place in the world you’d expect to find it, it’s in the Karoo.”
Jeanne Timmons (@most mammoths) is a New Hampshire-based freelance writer who blogs about paleontology and archeology at most mammoths.wordpress.com.
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