This is the story of the  time the world almost ended.

It’s also the story of a single, humble animal that was determined to go down swinging. Lystrosaurus was a little pig-like  creature, and though the animals themselves couldn’t have ever known it, they helped  us understand our planet’s history better.

By looking at their fossils, we can  tell a lot about these creatures, how the world changed around them in  horrible ways, and how they survived. And despite being quite well-studied, these ugly little guys are  still teaching us new things. Hold it, Hank!

I will not stand for this slander. I think they’re charming and delightful. Even loveable!

This is our good friend Emily Graslie, here to take over this episode and I guess  correct my natural history hot takes. Thanks, Hank! [♪ INTRO] These loveable little guys first  appeared in a period of Earth’s history known as the late Permian, about  259 to 251 million years ago. This was a world where instead of  having multiple different continents, pretty much all of the land on  Earth was smushed into the dry, fairly desert-y supercontinent known as Pangaea, surrounded by a seemingly endless super-ocean.

Lystrosaurus in life was a plant-eater. It was usually the size of a pig,  but could be as big as a small hippo. It was a distant relative of modern mammals; closer to us than to dinosaurs, for example.

It had a waddle-like gait, strong limbs  that may have been used for digging, and powerful jaws with a turtle-like  beak and two tusks on the side. Lystrosaurus was likely a kind of generalist, not specialized to go after any particular food, but able to survive off a wide range of diets. And this un-pickiness may have served them well, because toward the end of the Permian, the world wouldn’t have  been an easy place to live.

In fact, things were changing fast. South Africa’s Karoo Basin is a site that provides a pretty good snapshot of the end of the Permian. Studies of the fossil record there,  such as one described in a paper published in 2021 examining extinction  patterns in the Karoo Basin, have looked at how things changed  over a span of about 4 million years.

The researchers counted the  diversity of different species, as well as their abundance. And extinction rates in the Karoo  Basin appear to go up over time. But little Lystro was the exception.

They were what scientists call a disaster taxon: an organism that can thrive under harsh conditions and quickly repopulate an  area after a natural disaster. Unlike most species, Lystrosaurus  fossils actually went up, as a total number and as a  proportion of the overall fossils. Toward the end of the Permian, more than half of the specimens the researchers  uncovered were Lystrosaurus.

Things all over were ramping  up to a really bad time. The Great Dying is more formally  known as the End-Permian Extinction, or the Permian-Triassic Extinction. And it might have been the  closest we’ve ever come to life on Earth going extinct altogether.

It seems like it happened more gradually on land and rapidly in the ocean, but  no one was having any fun. We think what happened was  that a bunch of volcanoes began erupting in Northern  Pangaea, where Siberia is today. But if you’re picturing one or two  volcanoes blowing their top, don’t.

These eruptions weren’t like  anything we’ve seen today. Think Hawai’i, but turbo-charged. The eruptions lasted a long  time and covered a huge area.

They would have had cascading  effects and triggered massive, relatively sudden climate change across the globe, throwing ecosystems out of whack. Temperatures rose, ocean waters turned acidic and oxygen-poor, and food chains collapsed. It’s estimated that something  like 81% of all marine species and 70% of land vertebrate  species died off during this time.

Remarkably, though, one of the few land vertebrates to survive  was little Lystrosaurus. They, along with the other survivors, marched  into a new period called the Triassic. Times were still tough in  the early Triassic, though.

Many communities were still  unstable after the extinction event. Lystrosaurus fossils from the  Karoo Basin are helpful again here. Many Triassic Lystrosaurus specimens in the basin are notably different from their Permian kin.

A lot of the individuals are smaller,  more corgi-sized than hippo-sized, and the microscopic structure  of their bones is different too. From growth patterns in their bones,  it seems like many of the animals were still growing rapidly  at the time of their death. This suggests that a higher percentage  of Lystrosaurus individuals were dying as juveniles before they were fully  grown, and probably had to reproduce earlier in their life cycle to have  a chance at passing on their genes.

That said, evidence suggests there were havens. Researchers have also carried out  excavations in the Jiucaiyuan Formation in the Xinjiang region of northwestern China. Those digs suggest that, while  much of the world was experiencing rapid changes in vegetation,  there may have been a relatively stable confluence of rivers and conifer  forests in the very early Triassic.

This greenery would have supported  animals like Lystrosaurus. And the safe haven may, again,  be visible in their bones. That’s according to another  paper published in 2021 that studied Lystrosaurus growth  and life history at this site.

Excavations by the team in the  Jiucaiyuan Formation suggest that Triassic Lystrosaurus got bigger there  compared to those from South Africa. Though, stop-and-start growth patterns suggest they still had to deal with tough times. Now, it’s thought that different Lystro  species lived in north China and South Africa.

But the scientists suggest  the vegetation and a gentler, more stable environment may  have also played a role. So from Lystrosaurus, we learn that  while the Earth was going through a dramatic crisis, the changes  weren’t the same everywhere, and they didn’t all happen at the same time. The effects were varied,  and relatively stable havens likely did exist at different times.

Lystrosaurus’ resilience would pay off in the end. For a brief time in the Early Triassic,  it would even make up a ridiculously high percentage of vertebrate life on Earth,  including 70% of what’s found at Karoo. The dicynodonts, the two-tusked  group of which ol’ Lystro is a part, would continue to be successful.

The largest ever, descended  from a relative of Lystrosaurus, was nearly the size of an elephant. Unfortunately, nothing lasts forever. Today, there are no living descendants  of Lystrosaurus or any other dicynodont, which means their legacy now  belongs to the fossil record.

But thanks to work at places like  the digs in Africa and China, we can learn how a flexible, unpicky, and yes, even adorable little plant-eater survived and even thrived during a time of biological crisis. Not only that, but its story is also  one of how the world around it changed, often harshly, but with moments  of peace here and there. Thanks for watching, everyone!

I’m so glad I could join you today. Thanks to everybody, including the  researchers, who helped make this video. If you enjoyed it and you  want to get more involved with SciShow’s community,  check out patreon.com/scishow. [♪ OUTRO]