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Episode 227: The Great Dying

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It’s another extinction event episode! This one’s about the end-Permian AKA the Permian-Triassic AKA the GREAT DYING.

Further Reading:

Ancient mini-sharks lived longer than thought

Lystrosaurus’s fossilized skeleton:

Lystrosaurus may have looked something like this but I hope not:

This artist’s rendition of lystrosaurus looks a little less horrific but it might not be any more accurate:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

It’s time for our next extinction event episode, and this week it’s the big one. Not the extinction event that killed the dinosaurs, but one you may not have heard of, one that almost destroyed all life on earth. I mean, obviously it didn’t and things are fine now, but it was touch and go there for a while. It’s the Permian-Triassic extinction event, or end-Permian, which took place just over 250 million years ago. It was so bad that scientists who aren’t given to hyperbole refer to it as the Great Dying.

Don’t worry, we won’t talk about extinction the whole time. We’ll also learn about some interesting animals that survived the extinction event and did just fine afterwards.

We have a better idea of what happened at the end of the Permian than we have about the earlier extinction events we talked about in episodes 205 and 214. Right about 252 million years ago, something caused a massive volcanic eruptive event in what is now Siberia. Some researchers speculate that the cause of the volcanic eruptions may have been a huge asteroid impact on the other side of the Earth, which was so powerful that it caused magma to move away from the impact like water sloshing in a jostled glass. The magma rose up toward the earth’s crust and eventually through it onto the surface.

The result was probably the largest volcanic event in the last half-billion years and it continued for an estimated two million years. Most of the eruptions were probably pretty low-key, just runny lava pouring out of vents in the ground, but there was just so much of it. Lava covered almost a million square miles of land, or 2.6 million square km. Ash and toxic gases from some eruptions also ended up high in the atmosphere, but one big problem was that the lava poured through sediments full of organic material in the process of turning into coal. Lava, of course, is molten rock and it’s incredibly hot. It’s certainly hot enough to burn a bunch of young coal beds, which added more ash and toxic gases to the air—so much ash that shallow water throughout the entire world became choked with ash.

The carbon dioxide released by all that burning coal caused severe ocean acidification and ocean anoxia—a lack of oxygen in the water. But it gets worse! A lot of lava erupted into the ocean right at the continental shelf, where the shallow coastal water becomes much deeper. This is exactly the place where you find methane deposits in the sediments on the ocean floor. When those deposits were suddenly disturbed by lava flowing into them, all the methane in the formerly tranquil depths was released and bubbled to the surface. Methane is a powerful greenhouse gas, meaning that if a whole lot of it ends up in the atmosphere in a short amount of time, it can cause rapid global warming—much faster than that caused by carbon dioxide. This global warming would have happened after a period of global cooling due to reduced sunlight reaching the earth through ash clouds, which lasted long enough and was severe enough that sea levels dropped as glaciers formed. Then everything heated way, way up. The ice caps melted, which may have led to a stagnation of ocean currents. This in turn would have contributed to the water’s anoxicity and toxicity. The average temperature of the ocean would have increased by almost 15 degrees Fahrenheit, or 8 degrees Celsius. Atmospheric warming may have been as much as 68 degrees Fahrenheit in places, or 20 degrees Celsius. That’s not the average temperature of the world, that’s the temperature increase.

So, basically, everything was terrible and it happened very quickly in geologic terms. A 2018 study found that everything looked pretty much fine for the 30,000 years leading up to the great dying. Some researchers even think the initial extinction event might have taken place over just a few centuries.

Marine animals were affected the most, especially marine invertebrates. Trilobites and placoderms went extinct, eurypterids went extinct, and corals went extinct until about 14 million years later when modern corals developed. Some researchers estimate that 95% of all marine species went extinct.

Things were better on land, but not that much better. At the end of the Permian, life was good on land and it was especially good for insects because of the high percentage of oxygen in the air and the variety of plant life in huge swamps around the supercontinent Pangaea. The largest insects that ever lived were buzzing around in the Permian. This included an order of insects called Meganisoptera, or griffinflies. Griffinflies looked like dragonflies and may be related to them. Some species had a wingspan 28 inches across, or 71 cm. The arthropod Anthopleura, sometimes called the giant millipede, lived in the Permian too. Some species grew six feet long, or 2.5 meters, and were about 18 inches wide, or 45 cm. It looked like a millipede but had even more legs. It probably looked scary, but it only ate plants as far as we know.

Instead of actively breathing the way most vertebrates do, most invertebrates use a passive system to absorb oxygen from the air. This is great when there’s a lot of oxygen. When the level of oxygen drops, though, the largest species can’t absorb enough oxygen to function and die out rapidly. That’s one reason why you don’t have to worry about spiders the size of bears. So all the large invertebrates and a lot of the smaller ones went extinct as oxygen was replaced with carbon dioxide, methane, and other toxic gases in the atmosphere.

The acid rain caused by toxic gases and the reduced sunlight caused by ash in the atmosphere also killed off plants. Forests died, so that the fossil record during and after the extinction event contains massive amounts of fungal spores from fungi that decompose trees. Some researchers think all of the world’s trees died. Forests disappeared for some four million years. Since trees absorb carbon dioxide from the atmosphere and release oxygen, the lack of trees made oxygen levels drop even more.

Animals that depended on forests to survive also went extinct, including about two-thirds of all amphibians, reptiles, and therapsids. Therapsids were proto-mammals and it’s a good thing they didn’t all die out because they eventually gave rise to mammals.

Everything I’ve described sounds so incredibly bad, you may be wondering how anything survived. One stroke of luck was probably the size of Pangaea. That was the supercontinent made up of most of the world’s landmasses all smushed together. Before the extinction event, the middle of Pangaea was probably pretty dry with swampier climates around the edges. After the extinction event, the interior of the supercontinent was the safest place to be.

One of the most common land animals after the extinction event was a herbivore called Lystrosaurus. Lystrosaurus was a therapsid, and it was nothing exciting to look at unless you were also a lystrosaurus. Some species were the size of a cat while some were much larger, up to 8 feet long, or 2.5 m. It had a short snout, a short tail, and a semi-sprawling gait. A lizard walks with its legs stuck out to the sides, while a dog or cat or pig walks with its legs underneath its body. Lystrosaurus was somewhere between the two.

It probably lived in burrows that it dug with its strong front legs. While it had a pair of tusks that grew down from the upper jaw, those were its only teeth. Instead it probably had a turtle-like beak that helped it bite off pieces of vegetation.

Lystrosaurus lived in the central part of Pangaea, in what is now Asia, Antarctica, South Africa, and eastern Europe back when all those areas were all scrunched up close together. It survived the extinction event and expanded its range, and for millions of years it was almost the only big land animal in the world. It had almost no predators because they’d all gone extinct, and it had very few competitors for food because they’d all gone extinct. Lystrosaurus made up 90% of all land vertebrates for millions of years.

How did it survive when so many other animals died out? There are several theories, but the most important factor was probably its lack of specialization. It could survive on any kind of plant instead of needing to feed on specific species of plant. There’s also evidence that it could enter a torpor similar to hibernation where its metabolism slowed way down. This would have been a literal lifesaver during the time when the air and water were toxic and very little plant life survived. Lystrosaurus could hunker down in its burrow for long stretches of time, then come out and find enough food and water to keep it going for another stretch of torpor.

Just imagine the world back then, after the initial extinction event but before the world had recovered—say, a million years after the volcanic activity stopped. Picture a series of gentle rolling hills dotted with grazing animals. It’s peaceful and very open because there are no trees. Grass hasn’t evolved yet so the ground is covered in fern-like plants from the genus Dicroidium, which lives in dry conditions. As you look closer with your mind’s eye, you realize that every single one of those grazing animals—thousands of them visible in every direction—are the same kind of animal that looks sort of like a fuzzy pig with a stumpy lizard tail, clawed feet, and a turtle’s beak. Lystrosaurus, living the good life.

In the ocean, the situation was similar. The shallows were toxic waste dumps of ash where the water had so little oxygen that nothing could survive. But the deeper ocean was still livable for some animals.

For a long time, scientists thought a group of early sharks called cladodontomorphs had gone extinct during the great dying. Their distinctive teeth had been common in the fossil record, but after the extinction event they disappeared. Cladodontomorphs only grew about a foot long at most, or 30 cm, and may have had a weird-shaped dorsal fin that pointed forward. They lived in shallow coastal waters. You know, the worst possible place to be 252 million years ago.

Then palaeontologists found some of those teeth in rocks that were in much deeper water 135 million years ago. It turns out the little sharks had survived the extinction event by moving into the open ocean where conditions were better. And they didn’t just survive, they lasted for another 120 million years.

So let’s break it down. It was probably four million years before trees developed again from different plants. It was some 14 million years before coral reefs could rebuild as modern corals developed after their cousins went extinct. It took 30 million years for terrestrial vertebrates to recover from the great dying and 50 million years for all the ocean’s ecosystems to fully recover. That’s a colossally long time. But it did recover.

So what animals arose once the recovery was well underway? Icthyosaurs. Archosaurs, which eventually evolved into pterosaurs, crocodilians, dinosaurs, and birds. And therapsids that eventually gave rise to modern mammals.

I don’t usually tease the following week’s show, but next week we’re going to learn about some weird and interesting animals that developed in the early to mid Triassic, after the extinction event was over and life started evolving in new directions. As I’ve said in the previous extinction event episodes: no matter how bad things get, there’s always going to be some little animal stumping along out of the carnage to get on with the business of surviving and thriving.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 093: Insects Large and Small, mostly large

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Many thanks this week to listeners Bob, Nicholas, and Damian, who all suggested insects of one kind or another! So this week is an insect extravaganza, or at least we learn about some gigantic insects, the rarest insect in the world, and a tiny ant.

The Lord Howe Island phasmid:

The longest insect in the world:

The Queen Alexandra’s birdwing butterfly:

The Hercules beetle with random frog. Onward, my steed!

Further reading:

An article about phasmid eggs

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

I’ve received a bunch of excellent topic suggestions this year and I’m getting behind on addressing them, so the next few weeks will mostly be listener suggestions. This week we’re going to look at a topic several listeners have suggested…insects.

Now, you know insects are not my favorite, but they are definitely interesting. So thanks to listeners Bob, Nicholas, and Damian, we’re going to learn about various horrifying, I mean fascinating, insects!

We’ll start with some very small insects. I could probably do a whole episode just about ants, and maybe one day I will, but right now let’s look at a type of ant suggested by Bob. Bob lives in California and mentioned that the type of ant common in that part of the United States is the Argentine ant. It’s native to South America, specifically lowlands around the Paraná River, but it’s spread to many other parts of the world.

The Argentine ant is only about 2 to 3 mm long and are brownish in color. The queen ants are about twice the size of the worker ants, and each colony has many queens, unlike other ant species that may only have one queen per colony. Queen ants are the only ones that lay eggs. Worker ants find food and bring it back to the colony, tend the queen and her eggs, and dig the shallow nest where the colony lives.

Argentine ants are omnivorous, eating pretty much anything, and are definitely pests. They get into people’s kitchens to find food and will even make nests inside houses. Because a colony has more than one queen, the colonies are hard to eradicate. They also displace native ant species, which can impact the entire ecosystem since other animals that depend on native ants as their primary food won’t be able to find enough to eat. Argentine ants also cause problems for farmers, partly because they eat the larvae of pollinating insects, partly because they tend aphids for the honeydew that aphids secrete. Aphids are a pest to many crops, and the last thing farmers want is more aphids around—but Argentine ants want all the aphids they can get.

Researchers have found out something really unusual about Argentine ants. The ants that still live in their native habitat are genetically diverse and territorial, with different colonies fighting each other for nesting sites and hunting grounds. This keeps the population under control naturally. But outside of its native habitat, all the Argentine ants in the world are so genetically similar that in many cases, ants from different colonies act as though they were from the same colony. They don’t fight for territory, and instead act like a supercolony that can stretch for hundreds of miles, killing off or displacing native ants and other insect species.

But in some parts of North America, the Argentine ant is facing an ant species that may end up beating it at its own game. The Asian needle ant has started taking territory from the Argentine ant, helped by its resistance to cold weather. Both species of ant become less active in winter, but the Asian needle ant starts reproducing and foraging much earlier in the spring than the Argentine ant. This gives it a head start every year. Plus, the Asian needle ant is aggressive and has a venomous sting. Unfortunately, the Asian needle ant is just as bad an invasive species as the Argentine ant, driving out native ant species—and, in fact, it’s worse because some people are allergic to its sting.

Now let’s go from tiny ants to an insect I was terrified of as a kid, the stick insect, also called walking sticks or phasmids. I like the word phasmid. I don’t know why the idea of a stick insect was so scary to kid me, except that I liked to climb trees and I think I thought one day I’d climb a tree and discover that some of those sticks were not actually part of the tree. Nicholas suggests the Lord Howe Island phasmid in particular, which isn’t just a stick insect, it’s the rarest insect in the world. AND it’s enormous! In fact, it’s sometimes called the land lobster or tree lobster.

The Lord Howe Island phasmid can grow eight inches long, or 20 cm, and can weigh a full ounce, or 25 grams. Males are smaller than females. It has a round head with short antennae, sort of like a cricket, but its body is long and heavy with big legs. It’s black in color with no wings. It’s thicker than most stick insects and doesn’t so much resemble a stick as a cricket on steroids. I’m looking at a picture right now of someone holding one on the palm of their hand, and the insect is literally longer than their palm and almost as long as their palm and fingers. Put it down. Don’t touch it.

These days the Lord Howe Island phasmid lives in one place. That place is not Lord Howe Island off the coast of Australia. That’s where it used to live, and it was so common and so large that fishermen used it as bait. But rats and mice invaded the island in 1918, and by 1920 they’d eaten all the phasmids, which were declared extinct in 1960. But in 1964, someone found a dead phasmid on Ball’s Pyramid, a volcanic islet 12 miles, or 20 km, away from Lord Howe Island.

Ball’s Pyramid is what’s known as a volcanic stack, the eroded remnant of a volcano which is part of the submerged continent of Zealandia. It’s basically a cliff rising straight up out of the ocean. It’s the tallest volcanic stack in the world, 1,844 feet high, or 562 meters, 3,600 feet long, or 1,100 meters, and 980 feet wide, or 300 meters. It’s surrounded by rough seas and barely submerged rocks, and there’s pretty much nothing on it, so not very many people have ever tried to land on the islet. A group of mountain climbers scaled it in 1965 and again in 1979, but in 1982 access to the islet was restricted. It’s now part of the Lord Howe Island Marine Park.

During the successful climbs of Ball’s Pyramid, and a few unsuccessful climbs, dead phasmids were photographed but no live ones found. In 2001, a couple of entomologists landed to make a survey of the islet, primarily to determine whether the Lord Howe Island phasmid was alive on the island or actually extinct. They were pretty sure it was extinct. They found some Melaleuca howeana shrubs growing in a few cracks in the rock, and incidentally that’s a subspecies of tea tree that only grows on Ball’s Pyramid and Lord Howe Island. It grows up to ten feet tall, or 4 meters, and almost as wide. And in one of the shrubs they found 24 live Lord Howe Island phasmids.

Since then, eggs have been collected from the wild and relocated to a captive breeding program, which has been successful so far. Hopefully Lord Howe Island phasmids will be rereleased onto Lord Howe Island, once the rats and mice are eradicated.

Researchers think the Lord Howe Island phasmid was able to survive in such low numbers because females are able to reproduce without being fertilized by males, called parthenogenesis. Researchers have compared DNA taken from the Ball’s Pyramid insects to museum specimens gathered from Lord Howe Island prior to 1920 and determined that they are the same species.

The term phasmid, of course, refers to an order of insects that are mostly camouflaged to look like twigs or leaves, and it contains the longest insects in the world. And that’s good, because listener Damian wants to know about the biggest insects alive today.

The longest insect is Phryganistria chinensis Zhao, a stick insect only discovered in 2014 by researcher Zhao Li of the Insect Museum of West China. Locals in the mountains had told him about a massively long phasmid and he finally tracked one down. He brought it back alive to the museum, where it laid six eggs. Can you possibly imagine how excited he must have been by those eggs? When they hatched, the smallest of the babies was 26 centimeters long, or over ten inches. The adult female measured 62.4 cm, or just over two feet long. HOLY CRAP. TWO FEET LONG. That’s more of a walking branch than a walking stick. Not only that, its legs are almost as long as its body.

Since then, the babies have grown up and one of them, another female, is now the longest living insect ever measured, at 64 cm, or 25 inches. So you know what this means. It means there are some of them in the wild that are probably even longer.

Before the discovery of Zhao’s phasmid, the longest insect known was called Chan’s megastick, which was 22.3 inches long, or 56.7 cm. It was discovered in 2008 in Borneo in Southeast Asia, and only six specimens have ever been found. That means it too probably has even longer individuals living in the wild.

Many stick insects lay eggs that look like seeds. For a long time researchers weren’t sure why. After all, birds eat seeds. Why would an insect lay eggs that might attract hungry birds? But it turns out that the eggs contain a deposit of fat that attracts seed-eating ants, and the ants carry the eggs back to their nest and bury them. The eggs are then safe from birds, parasitic wasps, and other predators. We have come full circle back to ants, notice? Not only that, but researchers in Japan tested whether the protective coating on some seed-mimicking phasmid eggs would protect the eggs if they were eaten by birds. Sure enough, when they fed the eggs to the brown-eared bulbul, a bird known to eat phasmids, a few of the eggs survived and hatched. So it’s likely that phasmid eggs resemble seeds to attract ants but it’s okay if they also attract birds—in fact, it might even be a good thing since the birds would spread the eggs to new areas. Special thanks to Nicholas, who sent me links to several articles about stick insects, including the article about phasmid eggs. I’ll put a link in the show notes if you want to read the article, because it’s really interesting.

So the longest insects are phasmids, but what is the heaviest insect alive? That would be the Little Barrier Island giant weta from New Zealand, also called the wetapunga, which has weighed in at 72 grams, or over 2 ½ ounces. That’s heavier than some songbirds and mice. The wetapunga is basically an enormous cricket and somewhat resembles a gigantic, rather elongated version of one of my least favorite bugs, the cave cricket. It’s that same sort of sickly orangey tan color. If you look at it from the right angle it looks kind of like a lobster, which I also don’t like. Not only can the wetapunga be really heavy, it’s also long—not stick insect long, but a respectable four inches or so long, or 10 cm, and even longer if you count the stretched-out legs.

It eats plants and is mostly nocturnal.

Like the Lord Howe Island phasmid, the wetapunga is vulnerable to introduced predators. It only survives in the wild on Little Barrier Island, and is now the subject of a successful captive breeding program. It’s been around for 190 million years so it would be a shame to let it go extinct now.

The insect with the biggest wingspan is a butterfly called Queen Alexandra’s birdwing, which can have a wingspan almost a foot across, or over 25 cm. Its body is just over 3 inches long, or 8 cm. The female is larger than the male and has brown wings with pretty white and yellow markings. The male looks much different, with iridescent blue-green wings and a bright yellow abdomen. The butterfly is a strong flyer that spends a lot of time flying much higher that typical butterflies do. Males court females with a spectacular aerial dance.

The Queen Alexandra’s birdwing lives in eastern Papua New Guinea in a coastal rainforest, a habitat that is only about 40 square miles total, or 100 square km. Not only is it threatened by habitat loss due to palm oil plantations, which are absolutely insidious and seriously, you should stop buying products that use palm oil, but a volcanic eruption in the 1950s destroyed part of its habitat too. It’s protected and no one is supposed to buy, sell, or trade individuals, live or dead. Hopefully conservationists can work out a way to breed the butterfly in captivity.

The biggest beetle alive today is probably the Hercules beetle, which lives in the rainforests of Central and South America. It’s only longer than the titan beetle that lives in the Amazon rainforest because of its long rhinoceros-like horns, which push its length to 7 inches, or 17 cm. A male uses his horns to fight by grabbing another male with his horns and throwing him. The male Hercules beetle is black with yellowish or yellow-green wing cases. Females are usually all black and don’t have horns. Hercules beetle larvae are humongous and weigh a whopping 100 grams, or 3.5 ounces. So technically the Hercules beetle larva is the heaviest insect, but I’ve disqualified it because it’s not fully grown and anyway, it eats rotting wood. I wouldn’t be surprised if half its weight is just all the rotten wood it’s eaten. The adult beetles eat fruit.

So what about extinct insects? Were there ever insects even bigger than the ones alive today? The answer, as you may already know, is a big loud YES. Back in the early Permian era, around 290 million years ago, two species of flying insect called a griffinfly, which resembled a dragonfly, had a wingspan of almost two feet across, or 71 cm, and a body length of 17 inches, or 43 cm. Researchers estimate they may have weighed as much as a pound, or 450 grams.

If you were brave enough to listen to the spiders episode a few weeks ago, you may remember that spiders, and insects, can’t grow too big or they literally can’t get enough oxygen to function. So how did a huge active flying insect of that size manage?

One theory is that the atmosphere in the Permian contained more oxygen than the current level, which made it easier for insects to get the oxygen they needed. Air today is made of about 21% oxygen, with the other 80% made up of other gases, mostly nitrogen, but in the early Permian oxygen content was around 30%, although that was down from a peak of 35% only ten million years before. By the late Permian oxygen content had plunged to 16% and even reached as low as 12% at the beginning of the Triassic, killing off many animals and fragmenting populations of the ones that survived. Because the oxygen content was so low, animals could only survive at or near sea level. Even the lowest mountains were deadly because the air at higher elevations naturally contains less oxygen. Researchers estimate that breathing air with only 12% oxygen at sea level would be like breathing air at 17,400 feet, or 5,300 meters. Humans can’t survive at elevations above about 19,500 feet, or 5,950 meters. The reduction of oxygen in the atmosphere led to a massive extinction event called the Great Dying, where 90% of all marine life and almost 75% of all life on land went extinct around 251 million years ago.

Researchers aren’t sure what caused the de-oxygenation of the atmosphere, but it’s possible the massive volcanic activity near the end of the Permian played a part by releasing carbon dioxide and other gases into the atmosphere. The rock record during the Permian shows the results in stark detail: limestone in the older rock strata that’s full of fossils and the fossilized burrows of little animals that lived in the soft mud at the bottom of shallow oceans. Then there’s a mineralized layer of rock full of pyrite, which forms in low atmospheric conditions. Above this are bands of clay full of minerals from volcanic eruptions but with no fossils present. Above that are mudstone layers where fossils finally start appearing again in small numbers as life rebounded after the extinction event.

I’ve sort of gotten away from huge insects here, so I’ll finish by pointing out that clearly the phasmids of today aren’t having any issues with growing really big. So, you know, watch out where you put your hands when you’re climbing trees.

You can find Strange Animals Podcast online at strangeanimalspodcast.com. We’re on Twitter at strangebeasties and have a facebook page at facebook.com/strangeanimalspodcast. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or whatever platform you listen on. We also have a Patreon if you’d like to support us that way.

Thanks for listening!