We Are Nature

Hell Chicken Extinction

• Carnegie Museum of Natural History • Season 2 • Episode 4

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What dinosaurs and mammals survived the end of the Cretaceous, and why? What can we learn about resilience from survivors of past extinctions? What can we learn about adapting our culture and cities from the story of evolution? Featuring Matt Lamanna, Mary R. Dawson Curator of Vertebrate Paleontology at Carnegie Museum of Natural History, and John Wible, Curator of Mammals at Carnegie Museum of Natural History.

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Michael Pisano:

You're listening to the Anthropocene Archives, a presentation of We Are Nature. In this special series of stories, we're delving deep into Carnegie Museum of Natural History's 22 million collection items, raiding cabinets and cases, sifting through objects and organisms in search of stories of stewardship, solutions, and scientific wonder. On today's episode, mammals of the Late Mesozoic, a disastrous day for dinosaurs, and what we can learn about resilience from extinction survivors. Hop in, we're going to Hell Creek.

Michael Pisano:

Welcome to We Are Nature, a show about natural histories and livable futures. I'm your host, a collection of 206 bones, Michael Pisano, and today I'm joined by two expert bone collectors. Friends, would you please introduce yourselves?

John Wible:

I'm John Wible, Curator of Mammals, and I study everything about mammals, their origin, their evolution, their distribution on the planet today.

Michael Pisano:

Excellent.

Matt Lamanna:

And I'm Matt Lamana, Curator of Vertebrate Paleontology, and I study dinosaurs in particular, and especially dinosaurs from the southern hemisphere continents at the end of the age of dinosaurs.

Michael Pisano:

Excellent. Thank you both so much for joining me today and for bringing us behind the scenes of your respective collections here at the museum. I wanted to maybe start by hearing a little bit about those collections. So could you tell me about the vertebrate paleontology collection, the scope of it, scale?

Matt Lamanna:

Sure, sure. So the VP collection has um we think about 120,000 specimens in it. Um which sounds impressive, but we're actually quite small compared to some of the other collections, at least in terms of number of specimens.

Michael Pisano:

Oh sure, we've already talked to insects.

Matt Lamanna:

Yeah, no, totally.

Michael Pisano:

It's not a contest. 

Matt Lamanna:

Yeah, no, I think we have them on volume, but they um they have us on number for sure. Um but yeah, our collection ranges in age from I think the oldest, so we're fossils of backboned animals, so that's vertebrate paleontology. So, you know, fishes through amphibians, through reptiles, through birds, through mammals. Um and I think about the oldest fossil we have is in the ballpark of maybe 450 to 500 million years old. And then the youngest things we have are, you know, a few hundred years old, something like that.

Michael Pisano:

Excellent, excellent. And I want to hear the same thing about the mammal collection.

John Wible:

So we have about 130,000 specimens from all over the world.

Michael Pisano:

Probably go.

John Wible:

I know, yeah, from all continents except Antarctica, because there are no mammals that are native to Antarctica. There are some in the waters.

Michael Pisano:

Sure, whales, I imagine. Yep, that are hanging out there.

John Wible:

Um, and um we have a vast array of diversity, so we cover an incredible range of uh species that are around today, and a couple of species that are no longer with us, which is one of the things I'm gonna talk about today.

Michael Pisano:

Yes, I'm looking forward to getting into that. Um you mentioned diversity, and I wonder out there in the world, what is the diversity of mammals or the species of diversity?

John Wible:

Right. So there are about um 6,500 species today, and uh if you look at the major groups of mammals, about half of those 6,500 are rodents, those are things like uh chip munks and squirrels and beavers and things with ever growing incisors. A third of the diversity are bats, which usually surprises people how many different kinds of bats there are. And the remaining one-sixth is everything else. So all those things that you think of as mammals when you go to the zoo fit in that one-sixth of the diversity.

Michael Pisano:

Incredible. Um about the number of known dinosaurs. I know this is a very much an ongoing thing, but do you have a kind of broad tally of species diversity?

Matt Lamanna:

You know, that's a good question. Um, well, so what's one figure that's often quoted, and this surprises a lot of people, is that a new dinosaur, a new dinosaur often at least a species, um, usually a genus. So the the larger group that that you know, at least in the modern world, contains multiple species. A new genus of dinosaurs discovered um something like every two weeks. Um so, like, yeah, in my career, I've I've been involved with the discovery of um, I think it's 18 dinosaurs slash birds from the Cretaceous, um, and birds we think are descended from dinosaurs. And I think when people first hear that, they're like, wow, that's really cool and awesome. And then I tell them, oh yeah, well, we discover a new species every two weeks, so it's really not that big of a deal.

Michael Pisano:

I mean, I've been at this for a long time. It's quite an accomplishment, I'll say, either way. I have to imagine, not all of that is just, you know, paleontologists toiling out in the field digging up new things. There's also discovery that happens in places like this.

Matt Lamanna:

Oh, 100%. Absolutely. In fact, we um we likely have um a colleague of mine uh in Germany identified what's probably may well be a new species of dinosaur in our collection that we've actually had since 1903 or 1902, and nobody just recognized it, took the right eyes like coming along and seeing it to realize what it was. So yeah, like, yeah, and how many dinosaurs have been discovered thus far? Um, it depends on how many of these genera or species are valid. In other words, whether they're truly distinct from each other. Sure. Um, and I should back up a little bit and say a genus is like, you know, you can think like like our species Homo sapiens, the genus is homo, the species is sapiens, you know, tyrannosaurus rex, genus tyrannosaurus species tyrannosaurus rex. Um in the ballpark there, you're talking probably about a thousand and maybe more valid dinosaurs these days. Um and again, the number is increasing all the time.

Michael Pisano:

Which we love to see. Um, so we've got a bunch of beautiful things on the table that I want to talk about today. I think we should jump in. Um, and maybe we could start as a segue with one that I know you were involved with the discovery of.

Matt Lamanna:

Sure. So um this is uh the fossil that I brought that's nearest and dearest to my heart. Um so I mentioned that I've had the privilege to be involved with the naming of a bunch of new species of dinosaurs, and this is a piece of one of those.

MacKenzie Kimmel:

Collection item one is four and a half inches in length and half an inch in thickness. It tapers from a two-inch wide base to a keen point. It curves like a menacing blade. The fossil is a lustrous warm brown reminiscent of mineral-rich pottery. A shallow groove bisects its gently burnished surface. Can you identify collection item one?

Matt Lamanna:

So this is a claw from a hand. Uh it looks something like a um, you know, the blade on a scythe, like what a reaper, um, you know, the grim reaper is always shown with, you know, given that we're sort of in the proximity to Halloween. Yeah, exactly. Um but this um uh this claw would go on the hand of this dinosaur. Um uh it would be, and this is super cool too. So the when you see a fossil claw, you're only looking at the bony part, the bony core of the claw. And so just like, you know, just like me with my fingernail here, or if you have a cat at home and they're on their scratching post and they're losing their nails, basically, uh, this would have been covered with the same material, keratin, that that makes up our fingernails and and makes up cat claws and things like that. So the upshot there is that as big as this claw is, it would have been substantially bigger in life. Um, and so very, very formidable.

Michael Pisano:

Um and used for formidable ends. What what do you think? And maybe this is a time to introduce this organism, you know, who owned this claw?

Matt Lamanna:

Yeah, so this dinosaur is um a dinosaur called Anzu wyliei. It's a dinosaur that that uh again several friends and I named back in 2014. And um it, you know, when you look at this claw, you think instantaneously this animal's, you know, grabbing other things and eating them. Um and that may well be the case. But when we look at the rest of the anatomy of Anzu, it's a lot more like um if you know what the bird, like the a bird called the cassowary is. So they're you know, they look like an emu kind of with a crest on their head, um, sort of um the males have these bright blue faces. This animal, Anzu, looks like a giant cassowary with with elongate forelimbs tipped with claws, unlike the modern cassowary does. Um we jokingly call this thing the chicken from hell because it does look like kind of like a giant chicken. And so despite these, you know, sort of raptorial claws, a lot of the rest of the anatomy of Anzu sort of speaks to an omnivorous lifestyle, something that's eating both meat and plants, not unlike cassowarys do today. So cassowarys eat a lot of fruit. I think it's maybe the number one component of their diet. Um, but they'll also eat small vertebrates, so small, small backboned animals, you know, lizards, mammals, things like this. And I think it's probably fair to consider that Anzu may have done something similar in its environment. So it's a um sort of a jack of all trades, probably eating, you know, eating fruit, eating leaves, um, but also eating, you know, animal protein when it has the opportunity.

Michael Pisano:

And speaking of small prey, and this might take a little bit of context setting about when this creature uh was alive and where it was alive, I'm curious about the landscape and what other organisms would have been there, including perhaps what mammals were up to at that time.

Matt Lamanna:

Sure. Um so this animal comes from a rock unit called the Hell Creek Formation. It dates to about 68 to 66 million years ago and um crops out um over a broad swath of the Rocky Mountain region. So South Dakota, North Dakota, Montana. There are equivalent rocks in Alberta and uh and Wyoming, uh, Colorado, elsewhere. Um this animal would have roamed Western North America sometime between 68 and 66 million years ago. Back then, it was not the environment that we have today. Uh, it's often been our reconstructions of the environment have often been compared to, like, say, the Louisiana bayou or something like that. So humid, warm, very rich in vegetation, um, uh, you know, probably with, you know, with with wetlands in places and things like that. Um, as for the other animals that were living with this thing, it's like you look at this claw and you think, oh, maybe this thing's at the top of the food chain. Absolutely not the case. There were a bunch of things that wanted to make chicken nuggets out of a chicken from hell. Um, and uh and the most famous of those is Tyrannosaurus rex. And so this is what I brought here is a copy of a T. rex tooth. Um, so what I'm holding for people that are listening is um it's large and black, and I want to say about 10 inches long. Uh the part um uh the part that goes above the jaw, the part that you would see if you happen to be there when the animal opens its mouth and literally the last thing you saw.

Michael Pisano:

Right, unfortunately.

Matt Lamanna:

Exactly, it would be um, you know, this part about again, about maybe three and a half, four inches long, something like that. Um, the rest of this is the root of the tooth, and so would have sat inside the massive jaws of this thing. Um, and so you know, I don't think I need to describe a T. rex for viewers at home, but um, but this animal was absolutely the top of the food chain in the Hell Creek Formation ecosystem. And when I say formation, uh a formation is a set of rocks deposited in a specific time in a specific place, but you can think of it like a fossilized ecosystem, like so a fossil environment with animals and plants and you know, and and uh the the land, the whole landscape uh mixed in.

Michael Pisano:

You know, uh there's like maybe a common conception that mammals, their lifestyle is like scuttling around under the feet of these giant, you know, uh charismatic, fun animals. I don't hear a lot about mammals in the Cretaceous. I imagine it has to be a more complex picture than that. Would you give us a little bit?

John Wible:

So in the Hell Creek Formation, there's quite a mammal fauna that we already know about. Um but most of it is pretty small. Uh I would say the largest would have been maybe a cat size, maybe a small cat size. Uh most of the most of the mammals that would have been much smaller than that. Uh you can think of the mammals that were there probably in two different major groups, those that are related to things that are on the planet today, and those that have no relations whatsoever to anything. Um the proportions of those may be somewhat equal. Um so we had some holdovers coming from ancient uh Mesozoic groups that survived, and then we had these new forms that um show up uh before the Hell Creek formation, but then it continue on into the Cenozoic, into the age of mammals, right?

Michael Pisano:

And I think we'll let's let's wait on that because we are going to talk about that transition for sure. Can you take us back a little? I I imagine that it will require um like an infinite amount of glossing over, but can you give us a little bit of the evolution of mammals? When did we first start getting this you know group that now is so charismatic and feels so dominant in our culture?

John Wible:

Well, so it that's actually a kind of a hard question to answer because you're looking at a continuum of time and you're just gonna say, okay, where do I draw the line? So we've got this long lineage that arose with about the same time the dinosaurs did. So mammal ancestors have been around for hundreds of millions of years. Uh we like to say probably 200 million, 220, I mean something, something in that ballpark. Uh and then there was a very slow slog in terms of increasing mammalness, right? Taking on features that we that we associate with mammals today. Now, and one of the problems with that is that most of the features that we associate with mammals today are actually soft tissue features. So hair is one example. Um producing milk. I mean, these are things that we can't see. Well, actually, we can see hair in the fossil record if we're really lucky with the preservation. But most of them we can't really see. So um it just, you know, there are sort of arbitrary lines that get drawn in terms of talking about what those mammals were. The the bottom line is that for most of the extent of the Mesozoic mammals were really small.

Michael Pisano:

All right.

John Wible:

Um true size really does work. Uh something that gets up to like a cat or a small dog is a giant. Um most of the mammals we assume were nocturnal.

Michael Pisano:

Okay.

John Wible:

Um, and that may be our bias that we think that they couldn't survive with those big dinos chasing them around during the day. It's a convenient story, they were hiding during the day, came out at night. And but it's interesting because um we do have some reasons to think, at least for certain things, that they were nocturnal. So, for example, we know all a bunch of different gliding mammals were around during the Mesozoic, starting in the Jurassic. We had these beautiful preserved specimens that show us they have wing membranes. So we know that they were gliders. It's a thing like a living gliders are not. All living gliders are nocturnal. Right. So I it's like, is it gonna buck the trend in the past? Yeah, maybe it did. But those are the sorts of inferences that we can make based on modern mammals.

Michael Pisano:

Excellent. Thank you.

Matt Lamanna:

And there's there is evidence too, like for despite the overall small size, especially when you view it through today's lens of mammals, there's in addition to morphological diversity, like the way that you see with a you know gliding mammal versus a you know an insectivorous mammal or something like that, there's excellent evidence, and John has been a part of a bunch of these discoveries, um, for lots of ecological diversity in mammals as well. Like so there, we have evidence of digging mammals in the Jurassic and Cretaceous. We have, as John said, gliding mammals, swimming mammals. Um, of course, the you know, the the the animals that people think of when they think of mammals from the age of dinosaurs, little insectivorous things that are you know shrew-like things. There's uh a the one of the largest Mesozoic mammals, um, there's evidence that it preyed on dinosaurs, at least baby dinosaurs, some of the time. Um so it is absolutely true that mammals during the age of dinosaurs were on average much smaller than they are today. Um, but they do seem to have been more diverse than we were giving them credit for for a long time.

John Wible:

Yeah, one of the big advances that's happened in the last 50 years is the fact that we know so much more about Mesozoic mammals. I think in the early discovery days, when people were looking in the Mesozoic, they were looking for dinosaurs. And dinosaurs were easier to find than the mammals were. And now we have people with a totally different search image looking for tiny things. So we're discovering all sorts of things about the mammalian fauna. And Matt's right. I mean, the the diversity that we know, tree climbers, things that are terrestrial, I mean, it they're they're just they're all over the map. The only two niches that we we don't really have in the Mesozoic that we have today would be flyers.

Michael Pisano:

Sure.

John Wible:

So there's no dedicated flyers like bats that we know from the Mesozoic. And the other thing would be like whale-like things. So things that are dedicated to being aquatic. We have aquatic-like or what you would probably call semi-aquatic mammals.

Matt Lamanna:

Beaver or otter-like.

John Wible:

Beaver-like, yeah, muskrat, things like that. But nothing like a whale.

Michael Pisano:

Very cool. Well, so something very important happened in the evolution of mammals and dinosaur and bird lineages about 66 million years ago. I think most people are familiar, but could someone kind of describe that event very quickly?

Matt Lamanna:

Sure, I'll take a stab and John can fill in where I where I mess up. Um, but yeah, so uh 66 million years ago, uh non-avian dinosaurs, so we call what we call non-avian dinosaurs, so so all dinosaurs, with the exception of birds, um their descendants, birds, uh disappear from the planet seemingly globally. And the um the causal mechanism that most paleontologists and geo geologists agree on uh goes something like this. So a you know a giant, roughly six-mile-wide asteroid falls out of the sky, uh hits in what's now the Yucatan Peninsula. There's some evidence that that there may have been fragments of it that hit in other places as well, um, causes basically global environmental catastrophes. I mean, of course, everything at ground zero would be obliterated instantly, but but it was the longer-term um consequences of this that really I think had more profound um impacts on evolution and diversity. Um, so yeah, over the course of we're not really sure, you know, decades, hundreds of years, thousands of years, something, you know, hundreds of thousands of years, eventually, as a result of this event and its consequences, non-avian dinosaurs vanish from the planet, leaving only their descendants birds. Um, so birds are a tiny, uh, there's more than 11,000 species of birds today, but they are, in evolutionary terms, a tiny branch of the dinosaur evolutionary tree, and just that just so happen to be the group that we have today.

Michael Pisano:

Anzu, just to be clear, even though it has a lot of bird-like Hell chicken qualities, uh, is not technically in that group, right?

Matt Lamanna:

No, it's not.

Michael Pisano:

Can you talk about the distinctions?

Matt Lamanna:

Yeah, so that's that's an excellent question. And it's kind of gets to what John said is where do you draw the line between mammal and non-mammal? Where do you draw the line between dinosaur and bird? Um, the line is usually drawn at a famous fossil called Archaeopteryx. And this is this is a fossil that's well known to a lot of people. Um it's the it the logo for the Arcteryx clothing line of outdoor gear takes its, you know, is from the most famous specimen of Archaeopteryx, the Berlin specimen. Sure, it's got a yeah, exactly. It's neck pulled back and a very iconic fossil. Um, and so most paleontologists consider um Archaeopteryx to be the the what we call the earliest diverging or the most basal bird. So in other words, um, we don't like to use the word primitive, but the most sure the first bird, so to speak. Um and uh so if you're on the uh the bird side of Archaeopteryx, you're a bird. And if you're on the dinosaur side, you're a dinosaur. And Anzu is um Anzu is extremely bird-like. In fact, if you could take a time machine back 66 million years ago to say South Dakota and see one of these things in the flesh, your first guess would be wow, what a big, weird-looking bird. Um but it's it's evolutionarily speaking, it's not quite a bird because we don't think it's quite as closely related to modern birds as is Archaeopteryx, if that makes any sense whatsoever.

Michael Pisano:

I mean, we are humans, we strive to have these definitions, these boxes that, of course, messy.

Matt Lamanna:

Exactly, totally. Yeah. And um that being said, uh, we know from dinosaurs like Anzu and its relatives that a lot of the features that we associate with birds did not first evolve in birds. And so there are numerous species of feathered dinosaurs now. Um animals that again are less closely related to modern birds than is Archaeopteryx, and yet still have feathers, still have hollow bones, still have um uh a wishbone. A lot of the features that we associate with birds today we know actually date back to non-avian dinosaurs.

Michael Pisano:

I'm curious, and I know this is, you know, maybe a big question, but I'd love to hear you go back and forth about it a little bit. What was it that allowed birds and mammals to kind of pass through this long fallout period uh after the impact in the Yucatan?

John Wible:

Well, I can speak to the mammals and maybe I'll let uh Matt speak to the birds. So the the mammals, it's it's interesting. Um so the the the 10 million years after the uh extinction event, 66 million years ago, is a uh time that's known as the Paleocene. And the mammals that lived during the Paleocene show some interesting features that distinguish them from both uh those that went before and those that came after. One of the things that that's come out uh in the last few years is that they tend to be more robust than the mammals that were before and after. And so they had heavier bones, heavier features on those bones. And most of those are features that we associate with uh digging mammals. So I like to liken it that they're actually the ones that survived are the ones that could dig themselves into a den, a hole, and ride out the event that was killing everything else. Now that's somewhat fanciful, but it does seem to fit the data that there's a lot of of these sort of robust mammals that first are the first 10 million years.

Michael Pisano:

What does that kind of tell you about the fallout landscape? I feel like that might be helpful. Like if you were above ground, I'm sure globally there were many different variations, but what kind of happened, right? I mean, this thing hits the earth, I mean we imagine it kicked up a bunch of dust, plant growth was compromised. Can you guys just kind of elaborate, paint that scene?

Matt Lamanna:

Yeah, I mean, I think the picture is, you know, it sounds odd to say this 66 million years later, but I think the picture of that, of that day and the weeks that weeks, months, years that followed is still developing. Um but uh but yeah, there's uh for instance, there's a a good bit of evidence that they're basically the entire Earth virtually caught on fire due to these ejecta particles raining back down onto the planet, heating to ignition, think like uh, you know, anything like shooting star entering our atmosphere, you know, things like that. Um, you know, when that stuff hits the ground, it's gonna set any vegetate, you know, any dry vegetation at least on fire. You know, um, so yeah, there was a lot of um, there seems to have been a lot of uh, you know, sort of global firestorms. Uh, there certainly would have been, we have good evidence for this, that at least in the immediate region of the impact, there would have been massive tsunamis that were kicked up by this huge displacement of water with this big rock, Mount Everest sized rock falling into the water or partly into the water. Um so yeah, so um, and then of course, with you know, with with assuming that the you know, kicking dust into the atmosphere and having a lot of it stay there for a long time, assuming that's accurate, um, the the thinking is, as you said, photosynthesis, so plants, plants are compromised, um, but also temperatures drop as well. Um, it's often been likened to the you know, sort of um uh nuclear winters that were hypothesized during the Cold War. You know, the people that made it through a hypothetical war would still have to suffer consequences for quite a bit a bit of time afterwards. So so yeah, big giant rock falls out of the sky, tsunamis, you know, in the immediate vicinity at least, global firestorms, uh, dust in the atmosphere, compromised plants. Plants form the basis of the food chain. So once you knock out plants, you knock out everything else eventually, or almost everything else, as we know, life didn't completely go away. But um, but yeah, it would have been a really, really crappy day.

John Wible:

I liken it to um something that happened during my lifetime. You guys might be a little too young to remember this, Mount St. Helens. And I used to spend time in in that area and um both before and after. And it's amazing how quickly it came back. Yeah. So it was totally devastated. There was at least I don't know, six miles, ten miles of devastation where there was no life, seemingly no life. And yet within several years, greenery started to come back. And I, you know, I mean, so I liken it to that, that there's gonna be total devastation, but then there's a recovery phase that's that's gonna lead to life coming back.

Matt Lamanna:

And I'm glad, John, I'm glad you brought up volcanoes too, because I missed a big piece of the puzzle. Yeah, so there's this, yeah, there's a uh a um volcanic deposit in what's now India um called the Deccan Traps, and it's thought to have been um deposited over the course of a few million years leading up to the the end of the age of dinosaurs. So it's possible that you know that dinosaurs in non-avian dinosaurs and and other animals that went extinct uh at the what we call the Cretaceous Paleogene boundary, the KPG boundary, um endured lots of crises over the you know hundreds of millions of years that, or tens of millions of years that that they were around. Um dinosaurs first evolved about 235 million years ago went extinct 66, so you know, north of a hundred years, 100 million years. Um they endured a lot of different catastrophes. Um, and so it makes you wonder why was this one the one that did them in? I mean, obviously it was a a very big deal uh when it happened, um, but it also may have been, you know, they may have taken some body blows, so to speak, from you know, from the Deccan eruptions that, as we've seen, you know, volcanoes can cause pretty massive environmental disturbances too. And um-

John Wible:

And the scale of the Deccan Traps isn't it's like not just a little part of India.

Matt Lamanna:

Right.

John Wible:

It's a big part.

Matt Lamanna:

And over a vast, vast, vast amount of time. So, you know, a time a time scale of millions of years, a time scale that as people we can't really adequately comprehend.

John Wible:

Matt, I have a question for you about birds. So, what's the thinking today about how birds move across the boundaries?

Matt Lamanna:

Excellent question. So there's multiple hypotheses, I guess, and and it could be that, you know, it could be that none of them are right, it could be that many of them are partly right. Um, you know -

John Wible:

They may all be right.

Matt Lamanna:

I was gonna say it may not be a one-size fits all type thing.

Michael Pisano:

I appreciate the optimism.

Matt Lamanna:

Yeah. Um, but uh so one of the one of the most important things I think in this whole thing is that birds fly. You know, birds when you know when the going gets tough, they can get out of a bad situation maybe a little bit more easily than you know, something that's uh restricted to walking on a block two feet or two feet or four feet. Exactly. Yeah, so that's one thing. So their dispersal capabilities, their ability to move around the world is better than most other organisms at that time. Um, one idea that I have long entertained, I uh one of the places I work is Antarctica, and um some of the animals that we find down there from the end of the age of dinosaurs are birds that seem to be members of the of what we call the crown group, the anatomically modern bird group. In other words, more closely related to, in our case, things like ducks and geese than they are to things like, you know, like Archaeopteryx or more primitive Mesozoic birds. And so um, you know, we've long wondered, and we have very little evidence to back this up, but we've long wondered if the prevalence of modern birds or modern style birds in the at the end of the age of dinosaurs in Antarctica, where it's already, comparatively speaking, cold and dark, may have pre-adapted this group of birds to survive. And what's interesting, and something I didn't mention before, is that just like Mesozoic mammals, at the KPG boundary, there are lots of different kinds of birds around, including many that go extinct at the KPG boundary. So it wasn't just non-avian dinosaurs, it was a lot of different kinds of birds went extinct as well. And so what's interesting is Antarctica is one of the only places, if not the only place, where members of the modern bird group seem to be dominant at the end of the age of dinosaurs. And so, you know, is it is it coincidence? It easily could be. But could it be telling us something about, you know, the sort of pre adaptation to the cold and the dark, you know, sort of setting them up for success without, of course, them knowing it.

Michael Pisano:

I would say that that's another definition of robustness, certainly. And I wonder if -

Matt Lamanna:

Yeah, it really ties into some of the stuff that John was talking about. And I kept ooing and ah-ing when John was talking about that because I'd never I'd never heard that before. But this is fairly amazing. Yeah.

John Wible:

This is recent stuff that's come out.

Matt Lamanna:

And so the tie that binds with a lot of these things is, you know, in the cases of mammals, you know, maybe potentially burrowing, burrowing and waiting things out, birds potentially flying and moving, but also potentially already being adapted to situations like this. There's a newer hypothesis, too, and I don't know the details of it. It came out, I want to say, about five years ago, about um birds that were specialized in eating seeds may have done a little better too. Um so again, like a food source that will endure for a while. So the tie that binds is these animals that are, you know, kind of again, without intentionally doing this, evolution doesn't work like that. They're pre-adapted for disaster conditions, you know, and then from there, you know, the the groups that squeak through seem to, in the absence of or the near absence of competition from other things, seem to burst into you know these evolutionary radiations.

John Wible:

We have this concept of generalists and specialists.

Michael Pisano:

Yeah. Please expand on that.

John Wible:

Specialists, they can be great if the environment stays the same. But when the environment changes and you've specialized for one thing and that's no longer around anymore, these generalists sometimes went out. What was the environment like in Antarctica at that time?

Matt Lamanna:

Well, that's a that's an excellent, another excellent question, John. Um, it was undoubtedly much warmer than it is today. Um, we do have evidence for sea ice, at least in the winter, so it was cooler than most people think of the Mesozoic. Um it is geographically more or less in the same place it is now, so more or less at the bottom of the world. Um, the reason it wasn't frozen is um a combination of things, but it's um partly the overall warmer climate of the Cretaceous than we, you know, than we have today, but also partly too that Antarctica was still stuck on Australia and more or less stuck on South America, and that those continental connections um kept Antarctica from being thermally isolated. So nowadays Antarctica is surrounded by the Antarctic circumpolar current, and it acts like a Yeti cooler, kind of keeping the cold air in, um, and led to, you know, um more than, I can't remember off the top of my head when this is thought to have happened, but uh somewhere ballpark 10 to 20 million years ago, Antarctica goes through a deep freeze where this basically this goes runaway, and we get the big massive glaciation in Antarctica that we have now. But yeah, so the the to answer your question, John, uh Antarctica was much warmer. It still would have experienced several months of darkness and several months of light due to its latitudinal position. Um, we have excellent evidence of a diversity of non-avian dinosaurs, um, uh, multiple bird species. It was the rocks that we dig in down there were laid down in a shallow ocean. So we mostly find marine things like, you know, like um ammonites, these sort of things that are kind of like a squid inside a shell, um, sharks, uh, extinct marine reptiles called mosasaurs and plesiosaurs. It was a thriving ecosystem at the end of the age of dinosaurs down there. So, yes, absolutely Antarctica, much warmer than today, much more diverse um terrestrial fauna, uh, and of course marine fauna as well. And so, um, but yeah, among those were were birds that seem to be closely related to modern birds, and it may just may have been the you know some of the ones that squeaked through and gave ultimately gave rise to the birds we have today.

Michael Pisano:

This 66 million year ago boundary, the KPG boundary, is not the first mass extinction event in history of the Earth, right? Um, and each time there's kind of this evolutionary bottleneck, right? We get pushed through. Um I guess I wonder what we now, let's say humans facing climate change and other pressures on the environment, might learn about resilience from examining these mass extinctions, um, you know, about how we might adapt our cities, our civilization, our culture uh to be resilient now and in the future based on, you know, these organisms that we've talked about, the the robustness, the qualities of robustness. Um, what do you what would you think of that?

John Wible:

Um so so I guess we could talk about generalists and specialists in some regards, so that I could envision perhaps that you don't want to be too adapted to your environment that's right around you, because your environment might be changing.

Michael Pisano:

That's true.

John Wible:

So keep your options open in some regards. I that's a yeah.

Matt Lamanna:

I think it's a tough question because the you know, the key is, and you've heard me talk about, oh, you know, in the Cretaceous um, you know, like Antarctica was warmer than it is today. And you know, like when I first hear that, I'm sort of like, oh, you know, like maybe modern climate change isn't so bad, and things like that. And so what you have to remember is that we have, as far as I can remember, there's no evidence of the rate of climatic change that we're experiencing today in the fossil record. The closest thing we have is what's called the Paleocene-Eocene thermal maximum, around I want to say 55-ish million years ago, something like that. Yeah, yeah, yeah. Again, give or take a few million years, because I'm I'm good at that. Um, there's evidence of very rapid warming um at the PETM. But as far as I can remember, there's no evidence of even even the PETM does not approach the rate at which we are accelerating today. And so there's we certainly can learn a lot from the past from deep time when it comes to understanding the you know anthropogenic extinctions that are happening now, but it does seem to be in some ways unprecedented. And so that um, you know, that limits our ability to um to I think predict what's gonna happen, things like that. I think um to the to the uh question of generalists and specialists, I mean, you often this sort of gets at like kind of the you know sort of tongue-in-cheek thing that people say is you know, like when humanity's gone, it's just gonna be cockroaches and raccoons. And those two are those two are wonderful examples of generalists. That's why that's that's why that um you know that that uh sort of cliche has taken hold. Um but um I mean the bottom line is, you know, I mean, uh don't need me to tell you, and we've got to change our our you know some of the things that we're doing.

John Wible:

Um we really have a hard time predicting what what any of these events will mean down the road. So, for example, you as you pointed out, every time there's been these major climatic things in the past, it's shaken up the planet in terms of what the diversity of life was like. So at the PETM, we have a big changeover from these uh more primitive uh mammal groups to the modern groups, and that was really driven by those climatic changes. But the the Earth today is such a different place because the human the human species is so dominant over everything. So it's really hard to predict what the next step might be with similar sorts of climate change.

Michael Pisano:

Sure. I think yeah, that's a really excellent thing to point out. Um it doesn't stop us from acting on trying to mitigate what we do know uh is more problematic and is harmful to changing the climate faster than it's ever changed.

John Wible:

But I I should also point out that there's a place for studying the past. Yes, of course. Yeah, because it still is giving us the only window of data that we can have.

Matt Lamanna:

The closest thing we can do to running this experiment is to look what look what happened when the experiment was, in a sense, run in the past. You know.

Michael Pisano:

Very well put. 250,000 thanks to John and Matt for inviting us into the Carnegie's mammal and vertebrate paleontology collections, and to the many items therein for lessons in robustness, resilience, and wonder. We actually talked about a whole additional set of collection items from the mammal collection that didn't make it into this episode. So we'll be back with a part two featuring John, Matt, and more lessons from a much more recent extinction. We Are Nature is produced by Nicole Heller and Sloan MacRae. It's recorded at Carnegie Museum of Natural History by Matt Unger and Garrick Schmidt. DJ Thermos makes the music, Mackenzie Kimmel describes the collection items, and Garrick Schmidt and Michael Pisano, that's me, edit the podcast. Thanks for listening.