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Kallie Moore: Around 250 million years ago,

at the dawn of the Triassic Period,

life on Earth was on its knees.

This was the direct aftermath

of the most severe mass extinction event in history--

the Great Dying--triggered by colossal volcanic eruptions

and runaway global warming.

The Great Dying lasted hundreds of thousands of years,

leaving the supercontinent of Pangea scorched, desolate,

and unrecognizable from the rich and dynamic world

of the Permian Period that had preceded it.

More than 80% of the planet's species had been wiped out,

and its shattered ecosystems-- both on land and in the water--

were now inhabited only by a skeleton crew--

an eclectic band of survivors from the Permian,

the last remnants of the Paleozoic Era

of ancient life.

And foremost among them was

a tusked, beaked, and stocky herbivore,

about the size of a pig at most, called Lystrosaurus.

It's not the most immediately impressive of ancient beasts,

but in the Early Triassic, this little lumpy weirdo was

the poster child for life on land,

or what remained of it, at least.

Because, for a brief and, frankly, pretty bizarre moment

in the history of life,

after Earth had suffered its worst-ever mass extinction,

Lystrosaurus ruled over the wreckage.

It was the big winner of the apocalypse.

At some Early Triassic fossil sites,

Lystrosaurus is so abundant--

and other species so rare--

that it alone makes up more than 75% of the vertebrate fossils

that researchers find,

and as much as 95%, according to some estimates.

Lystrosaurus has earned the title of a "disaster taxon,"

a term that scientists give to groups that,

at least temporarily,

thrive in the aftermath of an ecological crisis.

So few other survivors emerged

from the rubble of the Great Dying that disaster taxa

like Lystrosaurus were suddenly freed

from nearly all competition.

And even though much of the Early Triassic was

still pretty hostile to most life,

Lystrosaurus was lucky enough to have

the right combination of traits to eke out a living,

or at least a surviving.

Gabriel-Philip Santos: So for a couple million years or so

following the end-Permian mass extinction,

the surface of the Earth was a mostly pretty bleak place:

hot, dry, almost totally treeless.

And in the water, a similar story was unfolding.

Marine life was devastated,

with only pockets of surviving biodiversity

clinging on here and there amongst the carnage.

The Triassic Period was off to a rough start,

but it wouldn't stay that way for long.

Blake de Pastino: Eventually, those survivors from the Permian

would find themselves replaced by a new wave of species,

and whole new complex ecosystems

unlike anything the world had ever seen before.

The Age of Reptiles was about to begin.

And while many features of the era of ancient life were

lost forever,

many now familiar features of the modern world emerged

as the planet recovered, too.

The aftermath of the Great Dying was

not just the graveyard of an old world

but also the cradle

of a new one.

Michelle Barboza-Ramirez: The five times

when almost everything died--

or the Big Five mass extinctions, as we call them--

are considered to be the most destructive events in evolution.

But the fossil record also shows

that mass extinctions aren't purely destructive forces.

By wiping the slate almost totally clean,

mass extinctions open up new opportunities

to surviving species that were beyond their reach before,

suddenly catapulting obscure groups

into the ecological spotlight.

And the pressure to survive those extreme events

molds species in ways that leave a lasting evolutionary legacy.

Ecosystems don't just recover from mass extinctions,

they often reform in ways that are radically different

from anything that existed before.

And after the Great Dying, life on Earth was changed forever.

This almost complete reorganization

left such a clear signal in the fossil record

that it literally marks

the end of the first era of complex life on Earth,

the Paleozoic, which means

the era of ancient life.

And the ecosystems that rose in life's middle era--

the Mesozoic--beginning

with the Triassic Period

were starkly different.

But that process took time,

and for basically all of the Early Triassic,

the ecological recovery on land was slow.

Having at least one really abundant species

from the Early Triassic gives us a rare and valuable window

into that world.

Because, while fossils of other species from this time

are sparse, we have thousands of Lystrosaurus.

Its tusks and beak allowed it to access

and feed on tough, dry-adapted vegetation,

and it could burrow into the ground

to find shelter from the elements

or from the occasional surviving predator.

Plus, its widespread distribution

across Pangea, from what's

now Russia to Antarctica,

suggests Lystrosaurus

colonized the far corners of the supercontinent

relatively quickly,

thanks to its resilience

and ability to tolerate

a wide range

of environmental conditions.

All of these traits,

probably combined with a healthy dose of luck,

allowed Lystrosaurus to survive and even flourish

in the wake of the Great Dying, when almost nobody else could.

Caroline Abbott: One of the things

that makes Lystrosaurus

such a great animal to study is that we

have it before the extinction

in the latest Permian,

during the extinction interval itself,

and then into the earliest recovery

from the extinction, the Triassic.

We have thousands of fossils of this animal,

and Lystrosaurus survived

the end-Permian mass extinction

in enormous numbers.

And in all those bones,

paleontologists have found clues that paint a picture

of a world reeling from environmental shock--

one so hostile that even so-called disaster taxa

struggled at times.

Most of the fossils that we find from Lystrosaurus

in the Triassic are quite tiny.

We get this huge overrepresentation

of juvenile specimens.

The fossil record shows that Lystrosaurus

from before the Great Dying lived up to around 14 years.

But after the event, patterns of bone growth show

that most individuals were only living around 2 to 3 years.

In the harsh, unforgiving world of the Early Triassic,

Lystrosaurus evolved to live fast and die young.

They likely reproduced earlier and more often

because of their reduced life expectancy

in these extreme conditions,

accounting for the abundance of juveniles in the fossil record.

In fact, its flexibility

in adapting its development and life cycle

may have been one of the key reasons that Lystrosaurus

was able to persevere as a disaster taxon.

But Lystrosaurus wasn't totally alone in the wreckage,

and some of the other survivors

were just as dangerous as the environment.

At the top of the fragile food chain

of the Karoo basin and elsewhere

in the first million years or so of the Early Triassic was

a leopard-sized therocephalian called Moschorhinus.

Before the extinction, Moschorhinus had been

just one of many medium- and large-sized carnivores that

stalked the landscape of Pangea,

along with the huge gorgonopsians

that were the apex predators of the Late Permian.

But while all those other big predators

disappear from the fossil record around the mass extinction,

Moschorhinus persists--the last large predator left standing.

Much like the Lystrosaurus it hunted,

the fossils of Moschorhinus show

that it was forever changed by the extinction event.

Remains of the predator from before and after

show several intriguing differences.

After the Great Dying, individuals are smaller,

and studies of their bone growth show that

while their growth period was shortened,

their rate of growth was actually faster.

This shrinkage seen in Moschorhinus, Lystrosaurus,

and potentially other Early Triassic species

has even been argued to partly explain

a widespread but little-understood

evolutionary phenomenon

dubbed the Lilliput Effect.

This is the same animal,

broadly speaking. It's the same genus?

Yes, yeah.

Before and after? Mm-hmm.

And that's significantly smaller than this.

Yes, yeah.

In paleontology, we find, oftentimes,

after mass extinctions,

small versions of the fossils

that we were seeing before the extinction.

But why? Like, what's the advantage of that?

Animals that are investing in a larger body plan

are not going to be able to get the nutrients...

Oh. to persist.

If you change your growth trajectory such that you're

a smaller animal that needs fewer resources,

you're growing fast at a smaller size

and reproducing more quickly.

That might be advantageous

to living in a catastrophic environment.

Being smaller but developing faster

might just be the evolutionary strategy

that consistently works best in a post-apocalyptic world.

But how did the ancestors of us mammals--known as cynodonts--

survive?

Was it just luck?

Or did we have some evolutionary tricks up our sleeves, too?

In the Permian, the early cynodont species

had never ever gotten big

or committed to highly specialized niches,

like so many other therapsids had during their heyday.

Instead, our cynodont ancestors had been

smallish generalist carnivores that lived

fast, energetic, and pretty scrappy lives,

chasing small prey and dodging predators,

kind of like the ferrets of their day.

You see, generalists tend to be much better

at coping with environmental instability than specialists,

who are highly adapted to and, therefore, very dependent on

specific ecological conditions.

And in the Early Triassic aftermath

lived cynodont survivors, like Thrinaxodon,

a weasel-sized ancient relative of ours that

shared its environment with Moschorhinus and Lystrosaurus.

We've found many of its fossil burrows,

sometimes with a Thrinaxodon still inside.

In fact, Thrinaxodon is

the earliest known burrowing cynodont.

This makes it quite a trendsetter,

seeing as around 50% of modern cynodonts--a.k.a. mammals--

still burrow today.

And scientists have even proposed that burrowing

may have emerged in Thrinaxodon and other cynodonts

as a direct adaptive response to the hostile environment

of the Great Dying and its aftermath.

It's a simple and common mammal behavior today that

may have roots stretching back to an ancient apocalypse,

and it's potentially one of the main reasons

we're still around.

This skeleton crew of animal life had it rough

for pretty much the entire Early Triassic.

They were surviving, but to even begin to recover

their former levels of diversity and abundance,

they first needed their habitats to recover.

And the geological record suggests

that may have taken a while.

See, researchers have identified a so-called "coal gap"

that spans about 5 million years

through the entire Early Triassic

and into the Middle,

where no rock layers from anywhere in the world

contain deposits of coal.

Now, coal is formed by the compression of peat,

which, in turn, is formed by accumulated plant material

in wetland swamps and forests.

So a lack of coal deposits in the geologic record

suggests an almost total loss of those plant ecosystems

for millions of years,

making it a pretty arid and barren phase of Earth's history.

So Pangea had lost its most diverse habitats--

forests and swamps--

and the marine realm had lost its equivalent, too--reefs.

See, while the fossil record on land shows a coal gap,

the marine fossil record shows a reef gap

that also lasts throughout the Early Triassic.

After being battered by rising temperatures,

ocean acidification, and a loss of oxygen,

80% of marine species died out.

From reef builders to trilobites to sea scorpions,

many ancient features of the world's oceans had vanished.

But there's evidence that in certain places

and at certain times during the aftermath,

a recovery was brewing below the waves.

For a long time, paleontologists thought

that while some groups achieved unlikely success here and there

in the Early Triassic,

rich and complex ecosystems still weren't really a thing

until 5 million to 10 million years later.

But in recent years, fossil discoveries

in places like here in Paris Canyon, Idaho,

have complicated that picture of Early Triassic Earth.

This site is way more exciting

than it might seem. Like, it's not that big--

it's only a couple hundred feet long--

and it's here on the side of the road, but it's

full of this really amazing combination of animals that

are really surprising.

And those animals are really important because they're

right in, like, the very beginnings of the Triassic,

really not that long after the Great Dying.

And they're helping us understand, like,

how ecosystems were really more complex

than we used to understand.

In 2017, paleontologists reported that

they had unexpectedly stumbled on something amazing here

buried in the rocks--

the fossil remains of a diverse marine ecosystem

from just around 249 million years ago,

less than three million years after the extinction event,

when this area was a warm, shallow sea

on the western edge of Pangea, close to the equator.

It featured fishes, cephalopods,

crustaceans and other arthropods,

sponges, bivalves, brachiopods, and more,

all somehow thriving together

when they should have been, well, dead.

This assemblage of species, known as the Paris biota,

was a strange mix of ancient holdovers from the Permian

and new species that show up for the first time.

Brandon Peecook: Oh, here we go.

Cool.

Right there. That spiral.

That's cool. What is that?

Yeah, that's an ammonoid.

So it's an animal called Tirolites.

It's super, super common.

We should find it a bunch in here.

This is one of the animals that actually lets us know

how old the site is.

There's another one right there.

Oh, my g--Yeah, I told you. They're everywhere.

They really are.

What other kind of creatures

can we find in here?

So things like squids and octopuses

and cuttlefish today, they first show up

in the Triassic, and some of the oldest fossils we have,

they're called coleoids.

That whole group are, like, known

from this site, like, right here.

But then there's also animals we find here that, like,

shocked everybody when they were first found

because some of them are animals that,

like, disappeared hundreds of millions of years ago,

or so we thought. Uh-huh.

But here they are in the early Triassic,

like, next to the lobsters.

Yeah, this is a little clam, so, like, a bivalve.

Oh! Like the little shell?

Yeah. It's pretty cute.

We've seen some brachiopods already,

but that's, like, a nice, nice clam,

so a different kind of little shelly guy.

This diverse community somehow stitched together

a functioning complex ecosystem in the wake of the Great Dying,

millions of years earlier

than many scientists had assumed was possible.

And since the discovery of the Paris biota,

similar evidence

of rapidly recovering shallow marine ecosystems

have turned up elsewhere,

including in neighboring Nevada and even as far away as China,

dating to as little as just 1 million years

after the extinction event.

We understand and expect to see

ecosystems not really recovering

from the Great Dying until, you know,

7 million, 8 million, 9 million years

after the event.

But this site's much, much closer to the event

than that, and it's already, like, really complicated.

So there's a lot of surprises, right?

There's a lot of geographic variety probably

in how life survived and recovered

from the Great Dying,

which is really, really, I think, exciting.

It means there's so much more to learn.

We still have a lot of open questions about

how such rich ecosystems could recover so fast

from the worst disaster of all time.

And in the years to come,

we may find the answers to those questions.

But it's already clear that,

at least in pockets of the marine realm,

life was showing just how resilient it really was.

A new group of predatory reptiles was on the rise

in the oceans of the Triassic: ichthyosaurs.

Ichthyosaurs, literally "fish-lizards,"

descended from land-dwelling reptiles

that gave up on the terrestrial realm entirely

and took to the water instead,

sometime around the Great Dying or maybe even a little before.

The first real ichthyosaur fossils we have

are coming, like,

right after the end-Permian mass extinction.

And so you have to realize that, like,

the extinction is an opportunity,

and ichthyosaurs are one of these groups that,

like, really takes advantage

and becomes full ocean reptiles.

With so little competition

in the aftermath of the extinction,

ichthyosaurs diversified rapidly,

as parts of many other complex open-ocean food chains

were recovering.

And while they started small,

within just a few million years, some of them would become

the largest animals the world had ever seen.

And by the Late Triassic,

some even rivaled modern whales in size.

The sudden rise of ichthyosaurs in the wake of the Great Dying

led to the first true ocean giants of Planet Earth,

a feature of our oceans that we've had

in some form or another ever since.

Eventually, above the waves,

life on land began to recover, too.

About 10 million years after the Great Dying,

we see evidence that the landscape of Pangea

wasn't so desolate anymore.

Dense forests regrew and spread across the world,

providing habitats for new species.

This global reforestation left signals in the geologic record,

like coal deposits showing up again

as the vegetation that formed them returned,

ending the coal gap.

And wood-boring beetles start showing up again

in the fossil record, too,

reemerging after a gap of their own at this time

as their forest habitats recovered.

Complex terrestrial ecosystems were reforming,

but this new era of life on land

would be different from anything that had come before.

As the Triassic recovery played out,

synapsids, including our cynodont ancestors,

found themselves facing intense competition,

and it came from their ancient cousins

from the other side of the amniote family tree.

The Triassic marked the start of the Age of Reptiles,

and their dominance of terrestrial ecosystems

would last for a very long time.

If Lystrosaurus was so what,

resilient and adaptive as a generalist

and it survived the thing

that destroyed almost all of life on Earth...

Yeah.

then what happened to them? How did their story end?

So Lystrosaurus

didn't live that far after the Early Triassic.

It was really abundant in the recovery interval

from the extinction.

But then as ecosystems return to normal

and we start seeing a higher diversity of species

going into the later parts of the Triassic,

Lystrosaurus disappears pretty quickly.

You would think that if it's so good at surviving

the worst thing that has ever happened to life on earth,

that it would be fine competing

with a few reptiles and Archosaurs

and other dicynodonts

that are persisting. But, no.

That's really remarkable. Yeah.

That's a heck of an evolutionary strategy.

Like, when things go wrong,

that's when they're really in their prime.

And then when things settle down again,

the conditions become more difficult for them.

Yes. Yeah.

It's like they're adapted to chaos.

Just as ichthyosaurs were

the rising stars of the Triassic oceans,

another group of reptiles was vying for ecological prominence

on land--the archosaurs.

They started out as a pretty obscure reptile lineage

that survived through the Great Dying.

And as the planet recovered

over the course of the Triassic Period,

they underwent an explosive evolutionary radiation.

Archosaurs began filling an array of ecological niches

that had been left mostly empty by the mass extinction,

outcompeting and replacing disaster taxa like Lystrosaurus.

Take the pseudosuchians, for example,

a branch of ancient archosaurs related to modern crocs.

They diversified into everything

from giant apex predators to armored herbivores.

One group of archosaurs, known as the pterosaurs,

even took to the skies,

becoming the first known vertebrates in history

to master powered flight.

And somewhere in this explosion of reptile diversity

was a lineage of upright, slender archosaurs

that was about to give rise

to one of the most spectacular animal dynasties

the world ever saw: the dinosaurs.

The earliest true dinosaurs arose

about 233 million years ago.

And they were only side characters

compared to other branches of the archosaur family tree.

But during the Late Triassic, that suddenly changed.

Much of that archosaur competition on land fell away,

and dinosaurs were catapulted to the ecological forefront.

And just in time, too, because Pangea was starting to break up,

and its fragments would carry the dinosaurs over the globe

over the course of the Mesozoic Era.

Their reign over Planet Earth had begun,

but that's a story for another time.

The Paleozoic Era of ancient life was

well and truly over,

and life's middle era, the Mesozoic, was in full swing.

But the story of the synapsids

that had lived and died on Pangea continued

into the Age of Reptiles.

Because scurrying here and there,

rustling through the undergrowth of dense Late Triassic forests,

a pretty familiar group had finally emerged: mammals.

They had evolved from a lineage of cynodonts

that had been both lucky and scrappy enough to survive

not just the Great Dying

but also the challenging

and increasingly competitive world of the Triassic.

And by the Triassic's end,

cynodonts were the only synapsids left.

Today, we mammals are the last remaining branch

of what used to be a huge, diverse,

and once-globally successful synapsid family tree,

with roots stretching back to the era of ancient life.

While synapsids had seemed unstoppable in the Permian,

in this world dominated by dinosaurs,

the earliest mammals became mostly small and nocturnal

to survive--

quite literally cast into the shadows.

Dimetrodon...

The Permian, in my eyes,

is more important than the dinosaur age

because this is where our roots come from.

You know, your cousin is buried right here

290 million years ago.

Christopher Flis: This is where humanity comes from in a sense,

and it's always surprising us.

You know, every time we think we know something new

about the Permian, it changes our minds.

The Permian is a really important

time period because it is so early

in the evolution of life on land.

And we're really getting a snapshot

of how vertebrae animals

were exploring how to live in this new place.

This is sort of where the ancestors of the mammals

show up--our ancestors.

These dinosaurs that aren't dinosaurs, really.

Rrr!

When you get, like, a pack of dinosaur toys,

and it's in there for some reason.

You know, you look at a Dimetrodon,

you're like, "Oh, that's a dinosaur."

But they're not dinosaurs.

They're actually a close relative of mammals.

Dimetrodon and the Edaphosaurus,

they are still very relevant.

The synapsid body plan,

the idea that something could look and act

more or less like the mammals would later on

simply isn't likely just like any form of life.

And so the fact that not only did that happen

but we have such a good record of it here,

that success story is just really cool.

Without this Great Dying,

we wouldn't have had Age of Dinosaurs as we saw it.

So, you know, for a paleontology person,

that's kind of cool.

But I'm a human first, so I'm team synapsid.

So the fact that they were knocked out,

some of the traits that were required

to survive this event led to us mammals--

assuming you're a mammal watching this--

rising up again and, in the Cenozoic,

taking it from there on.

And so that's why it's such a big deal that

we were knocked back

to appreciate where we are today.

With something as terrifying as the Great Dying,

you know, when almost all life was wiped out,

it's pretty inspiring in a way

to be able to see life just carry on

and be resilient.

Studying the Permian is really important

because we can really understand so much of our story from that.

This is when so many things go extinct.

This is when so many things recover.

It's that really incredible story of life on earth,

and being able to see it through the lens of the Permian

and how life and death on Pangea was happening,

it's... it's just really, really cool!

Today, we're finally bringing

the epic saga of the Permian Period

back into the light with us.

Because while the world of the Permian is long gone,

it is no longer forgotten.

And while it still doesn't always get

as much attention as it deserves,

considering it was both the best and the absolute worst

of evolutionary times--

its story is one that we're slowly rediscovering.

252 million years after the Permian ended,

at least some descendants

of the species that lived and died on Pangea

are coming to know what it means to be a living legacy

of one of the most pivotal and radical chapters of deep time.