Around 251 million years ago, groups of pig-sized herbivores with tusks and beaks piled up, died, shrivelled and then fossilized looking like crushed road kills , with impressions of their stony skin still present in the rocks around them.
These strange layers of fossils suggest that the recurring drought was a big problem for the animals, which belonged to the genus Lystrosaurus, meaning “shovel lizard” in ancient Greek. Lystrosaurus were rare survivors of the Permian-Triassic mass extinctiona period of runaway climate change 252 million years ago that killed around 70% of terrestrial 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 likely caused severe droughts on the supercontinent Pangea, which could have caused the death of this particular group of animals.
“As we observe today with global warming, it seems that [warming] increases the likelihood of extreme events,” said Pia Viglietti, postdoctoral fellow in earth sciences at the Field Museum of Natural History in Chicago. “Perhaps this is what happened in the first Triasthat there were these repeated dry spells that were happening more frequently.”
Live fast, die young
Researchers first discovered the fossils 11 years ago in the Karoo desert region of South Africa. During an excavation, they unearthed 170 tetrapods, or four-legged animals, in about 6.5 feet (2 meters) of sandstone, including several clusters of these lystrosaurs. These strange creatures were unlike any animal living on Earth today. They were part of a group called therapsids, an extinct order of reptiles that includes ancestors of mammals (mammals are the only descendants of therapsids that still persist today). They were shaped like a “bulldog with a beak and tusks,” Viglietti told Live Science.
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Lystrosaurids were herbivores and probably used their beaks to chew on tough vegetation. They seem to have experienced a demographic boom before and during the end of the Permian, about 252 million years ago. While everything else was busy dying, lystrosaurs were everywhere. But they may not have lived their best life. The new fossils come from the oldest Triassic, just after the end of the Permian. Most of the dead lystrosaurs were juveniles, which tend to be more susceptible to disasters like droughts, Viglietti said.
Related: The 5 mass extinctions that marked the history of the Earth
Lystrosaurs might have died off early immediately after the mass extinction, Viglietti said, and they may have made up for their shortened lifespans by reproducing earlier — a sort of “live fast, die young” way to survive a global cataclysm. (Previous studies have suggested that they slept through it.)
Fossils suggest that young lystrosaurids may have clustered together before they died, likely in a floodplain where they hoped to find water and vegetation. This type of behavior is still seen today during droughts in sub-Saharan Africa, Viglietti said, where animals congregate around dwindling water and food sources before succumbing to thirst and starvation.
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Two of the fossils found in the Karoo sandstones left skin imprints in the surrounding rock, indicating that the animals may have dried up and mummified soon after death, before being buried and fossilized. These two “mummies” were fossilized next to each other, limbs stretched out.
“They were both pushed aside, almost like they died going somewhere,” Viglietti said. “Literally stopped in their tracks.”
Lystrosaurids didn’t go extinct for a few million years. The fact that they lived while so many other species perished is sometimes held up as evidence that the planet recovered fairly quickly from the climatic mess at the end of the Permian, which was caused by huge Siberian volcanoes. spewing gases into the atmosphere. But the finding of a population struggling with the stress of repeated droughts suggests the Earth hasn’t recovered quickly at all, Viglietti said.
The discovery provides insight into how Earth might respond to the current climate crisis, Viglietti added.
“If we don’t mitigate our climate crisis, things won’t bounce back, not even within the lifetime of our species or perhaps other species that follow us,” Viglietti said. “Recovering from these events can take a long time.”
The results are in press in the journal Paleogeography, Paleoclimatology, Paleoecology.
Originally posted on Live Science.
Mummified, sprawling Triassic ‘shovel lizards’ look like roadkill and likely died in a drought