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Lystrosaurus: Survivor Story · Acedra
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Lystrosaurus: Survivor Story
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0:00
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,
0:26
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.
0:55
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.
1:19
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.
1:45
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.
2:10
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.
2:36
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.
3:02
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
3:28
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
3:53
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
4:18
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.
4:42
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.
5:07
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.
5:31
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.
5:57
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.
6:24
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]
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