These strange layers of fossils suggest that repeated drought was a big problem for the animals, which were members of the genus Lystrosaurus, which means “shovel lizard” in ancient Greek. Lystrosaurs were its rare survivors Permian-Triassic mass extinctiona period of sudden climate change 252 million years ago that killed about 70% of land vertebrates and 96% of marine animals. Newly analyzed fossils suggest that Lystrosaurus may have survived but not thrived. The climate change that killed so much life on Earth probably caused severe droughts on the supercontinent Pangaea, which could have caused the death of this particular group of animals. “As we are seeing today with global warming, it seems that [warming] it increases the likelihood of extreme events,” said Pia Viglietti, a postdoctoral fellow in Earth Sciences at the Field Museum of Natural History in Chicago. “That might have been happening earlier Triassicthat there were these recurring drought events that were happening more often.”
Live fast die young
Researchers first found the fossils 11 years ago in the Karoo desert region of South Africa. During one dig, they discovered 170 tetrapods, or four-legged animals, in about 6.5 feet (2 meters) of sandstone, including multiple clusters of these lystrosaurs. These strange creatures were unlike any animal on Earth today. They were part of a group called therapsids, an extinct order of reptiles that includes mammalian ancestors (mammals are the only descendants of therapsids that persist today). They were shaped like a “bulldog with a beak and some tusks,” Viglietti told Live Science.
A photograph of a Lystrosaurus fossil found in the field in South Africa. The “roadkill” look is evident, while the body position and skin impressions suggest that these animals died in drought and dried out before fossilizing. (Image credit: Roger Smith) (opens in new tab) Lystrosaurs were herbivores and likely used their beaks to chew tough vegetation. They seem to have experienced a population explosion before and during its end Permian, about 252 million years ago. While everything else was busy dying, Lystrosaurs were everywhere. But they may not have been living their best lives. The new fossils come from the earliest Triassic, immediately after the end of the Permian. Most of the dead lystrosaurs were juveniles, which tend to be more susceptible to disasters such as drought, Viglietti said. Lystrosaurs may have died early in the immediate aftermath of the mass extinction, Viglietti said, and may have made up for their reduced lifespans by reproducing earlier — a “live fast, die young” species to survive a global cataclysm. (Previous studies have suggested this as well slept through it.)
Dying together
The fossils suggest that young lystrosaurs may have huddled together before dying, possibly in a floodplain where they had hopes of finding water and vegetation. This type of behavior is still seen today during droughts in sub-Saharan Africa, Viglietti said, where animals gather around scarce water and food sources before succumbing to thirst and starvation.
Face to face with a Lystrosaurus fossil in the field. The animals appeared to have died in clumps, perhaps suggesting they were congregating around dwindling water supplies during a drought. (Image credit: Roger Smith) (opens in new tab) Two of the fossils found in the Karoo sandstones left skin impressions in the surrounding rock, indicating that the animals may have been dried and mummified quickly after death, before being buried and fossilized. These two “mummies” were fossilized next to each other, with their limbs sticking out. “They were both eagles, almost like they had died going somewhere,” Viglietti said. “They literally stopped in their tracks.” Lystrosaurs didn’t become extinct for another few million years. The fact that they lived at all when so many other species were lost is sometimes seen as evidence that the planet recovered fairly quickly from the end-Permian climate, which was caused by huge Siberian volcanoes belching gases into the atmosphere. But the discovery of a population struggling under the stress of repeated droughts suggests that Earth did not recover quickly at all, Viglietti said. This finding provides insight into how Earth might react to the current climate crisis, Viglietti added. “If we don’t mitigate our climate crisis, things won’t just recover, not in the lifetime of our species or possibly other species that come after us,” Viglietti said. “Recovery from these events can take a long time.” The findings are published in the journal Paleogeography, Paleoclimatology, Paleoecology. Originally published in Live Science.
