Journalist and author Susan Ewing talks about her new book Resurrecting the Shark: A Scientific Obsession and the Mavericks Who Solved the Mystery of a 270-Million-Year-Old Fossil. (And we'll discuss how Helicoprion is not technically a shark, but it's really close!)
Journalist and author Susan Ewing talks about her new book Resurrecting the Shark: A Scientific Obsession and the Mavericks Who Solved the Mystery of a 270-Million-Year-Old Fossil. (And we'll discuss how Helicoprion is not technically a shark, but it's really close!)
Steve Mirsky: Welcome to Scientific American's Science Talk, posted on July 21, 2017. I'm Steve Mirsky. On this episode:
Susan Ewing: But Helicoprion's teeth did not grow on the jaw, and the whorl was a single tooth that grew in the middle of the shark's jaw. It looked like a saw blade in the middle of that lower jaw, coming at you.
Mirsky: That's Susan Ewing. She's a journalist and author, and her new book is Resurrecting the Shark: A Scientific Obsession and the Mavericks Who Solved the Mystery of a 270 Million-Year-Old Fossil. And with Shark Week starting on July 23rd, we figured this was a great way to get into the spirit of giant, chomping, cartilaginous fish such as Helicoprion. Which is technically not really a shark, but it's so close, as we'll get into in the discussion, and which is distinguished by its bizarre whorl of teeth, its spiral of chompers, which is really just one massive tooth that looks like dozens. Let me let Ewing explain. She's based in Bozeman, Montana, so we talked by phone. Who would've thought there was such a thing as this beast?
Ewing: Oh, my – Nobody would've thought there was such a thing. That's why they could not figure out what it was. There was no analog, no context to it. And the thing that was so confusing about Helicoprion that confused so many people was that that tooth whorl was a midline structure. So it was like a pizza cutter stuck in a quart of ice cream, in the middle of the shark's lower jaw. And it's a shark-like animal, but I'm just gonna call it a shark because it looked like a shark.
And so there's no other animal that has something like that, and so that's why it was so confusing.
Mirsky: And a picture is really with a thousand words, or, in the case of your book, because you're a very efficient writer, maybe about 300 words. When you see the image, the illustration of the shark, then it becomes clear. But what we're talking about is, we're all used to teeth that are along the same line as the opening of our mouth. But for these guys, the teeth are actually perpendicular, like – it looks like a buzz-saw coming at –
Imagine the shark coming at you, and there's a buzz-saw that's in a vertical position that's coming at you. It's totally bizarre.
Ewing: Right, right, and the teeth don't spin, so the buzz-saw doesn't spin, but you're exactly right. Shark teeth, modern shark teeth, the teeth grow on the jaws. It's like this conveyor belt of teeth that form along the jaw and on the jaw, and then they fall off. Modern sharks, most people know, they shed thousands of teeth in their lifetime. But Helicoprion's teeth did not grow on the jaw, and the whorl was a single tooth that grew in the middle of the shark's jaw.
Just like you said, it looked like a sawblade in the middle of that lower jaw, coming at you.
Mirsky: And technically it's a single tooth, although it looks to us like many teeth arranged on a circle. But in reality, they all have the same substrate and they're just the crowns of – they're just many crowns coming up from that substrate.
Ewing: Right. That's right. So with one continuous root, the one continuous tooth root, that grew in a spiral, like the head of a fiddlehead fern. And the crowns that erupted off the tooth were tooth crowns, so they looked like shark teeth, but they're crowns. And it's kind of like, I use the example, it's like mushrooms are the fruiting bodies of the mycelium, the roots under the soil. So it was one tooth root with multiple crowns.
Mirsky: And this creature lived 270 to 280 million years ago.
Mirsky: So they're not gonna be coming at you if you're at the beach.
Ewing: Right [chuckling].
Mirsky: But what's fascinating is the story of the science of figuring this out. That's really the wonderful story here that you have woven. And it starts with the first discoveries of the fossils that look like – I mean, there are a lot of spirals in nature, and people didn't even realize that these were necessarily teeth when the first fossils were found. They looked like the other kinds of spiraled critters that are out there.
Ewing: Yeah, a lot of people mistook them for ammonites, if you know what those are. They're ancient sort of relatives of the nautiloids, and so they grew in spiral shells, and they're fairly common fossils. And they were in the cephalopod family, like the squid, octopus family. And so they have a really similar shape, and so at first glance, they look like ammonites. But then you look closer, and you see these big teeth on them. They're just bristling with teeth along the edges.
Mirsky: Yeah, and eventually – I mean, there are so many researchers that you mention in the book, going back into the – fossil hunters and researchers, going back into the 19th century. And eventually, I forget which one figures out, "Wait a minute – these are teeth."
Ewing: Karpinsky, Alexander Karpinsky. He was a very esteemed Russian geologist, and he loved oddball fossils. And his students – He had a reputation for having an open door for anything that was weird, so his students would come to him, or his colleagues would come to him, if they couldn't figure something out. And they'd say, "What is this?" And so actually a school inspector, Mr. Bessonov, somehow came into possession of the first full spiral that had been discovered.
And who knows who actually found it; it was probably a limestone miner somewhere in the Ural Mountains of Russia. And so Mr. Besonov just thought that these fossils might be important, and so he crated 'em up and shipped 'em all the way to St. Petersburg, to Karpinsky. And so they landed on Karpinsky's desk, and he is the one who identified and recognized that this fossil was from an animal that had not previously been identified.
And so Karpinsky is the one who named the beast Helicoprion from the Greek helico for "spiral" and prion for "saw."
Mirsky: And throughout the book you see such good behavior on the part of so many scientists, Karpinsky being a – I mean, you see bad behavior also – but Karpinsky being an example. When he writes up this very extensive monograph, he points out all the things that he does not know, and all the – He basically lays out a research plan for the rest of the scientific community.
Ewing: Yeah, that's exactly right. He was such an incredible man, of great intellect, and he also had a wonderful singing voice, as I read in the research. But, yeah, he did. And he was very forthcoming with what he believed he could say with certainty and what he just threw out there for other people to think about. His monograph on Helicoprion came out in 1899, and so most of the scientific inquiry really took off in the early 1900s.
Mirsky: Well, we also wanna give a lot of credit to Fanny Hitchcock, who had –
Ewing: Yes, thank you. Right.
Mirsky: She had to be a remarkable woman, because she was, first of all, a woman in this time in science, when it was almost uniformly men. And she's also not really affiliated with an institution, so she's freelancing.
Ewing: Exactly. And I could not find out where she was educated, and – or we don't know today. But she came from a prominent family, and she just kind of showed up on the scene fully educated. And she was the one that really had the key to the thinking about – It was actually before Helicoprion. There was another genus of Paleozoic shark-like animals that had tooth blades. And so Edestus was a different animal. But the Edestus fossils had been found before Helicoprion, and they were also these midline structures.
And what was so odd about them is most shark teeth have a front and a back, so you can tell which is the sort of cheek side and which is the throat side. But these Edestus fossils, and then later Helicoprion fossils, they were symmetrical, so they were bilaterally symmetrical. So if you cut a tooth down the middle, there was no front and back, and so that's what had everybody really scratching their heads, because there's just nothing like that.
So Fanny Hitchcock is the one who proposed that these were midline structures, but it was such a radical idea, with no analog, that the scientists, they pooh-poohed her. And they said, "Well, while Miss Fanny Hitchcock is a wonderful student of these things, she has no idea what she's talking about," basically. But she turn out to be the first person who identified that. And then that was a clue that helped them figure out Helicoprion down the line.
Mirsky: It's really a incredible leap of imagination to realize that the teeth are gonna be symmetrical if you rotate them 90 degrees, and suddenly they're this pizza cutter in the mouth, rather than a set of chompers in the mouth.
Ewing: Right, right. It really [laughter] really forced people to sort of think outside the tooth box. It was very, very unusual. And, I mean, that's why it was such a mystery for so long, and why so many scientists threw themselves into contortions keeping that tooth spiral out of the animal's mouth. They put it on its head. They put it curling up over its nose. They put it on its tail. They put it on its back. They put it – They wanted to put it everywhere except in the mouth.
And a few of them said, "Who could imagine a monster [laughter] with something like this in its mouth?" Because it was so big, too, these tooth whorls. An average-sized tooth whorl is the size of a large dinner platter, and they get bigger than that, so it's hard to imagine something like that in an animal's mouth. And that was the big – that was the final cliff to jump on really pinning down where the structure was on the animal and how it worked.
Mirsky: And the book also – If you're at all interested in a quick primer on the history of geology, you get it in this book as well. And one of the things that we learn about is the fact that you're gonna find the same fossils in the same layers laid down over geological time. And this became a big clue, because the whorls of teeth were being found in the same layer as a lot of squid fossils. And as you said in the book, that ain't a coincidence.
That's like saying it's a coincidence to find the fox footprints outside the chicken coop.
Ewing: Right, exactly. And that was one of the challenges about writing the book, is the scientific nuances of Helicoprion are so interesting, but in order to really understand how cool they are, and really get the important of it, you have to understand basics of geology and paleontology. And so I really wanted people to understand, to come along on this journey, and so that's why I tried to share the basics of geology and strata, and key fossils.
You can identify the age of rocks by what fossils are in them, and that's been knowledge that's accumulated over time through going out and finding all these fossils, and then looking at 'em and go, "Oh, well, look at this. This particular set of fossils always seems to be in this particular rock layer." I mean it's just – it's really interesting, and it gives you such an appreciation for earth processes. It's just really cool.
Mirsky: It's this gigantic planet-wide jigsaw puzzle that a few people, over the course of their lives – and we're talking about generations of people at this point – have decided to try to work on together, knowing that they're not gonna get it together in their own lifetimes, even, for a lot of them.
Ewing: Right. I say paleontology is not for the impatient. It's – And the same with geology. You just have to tinker your way along, and putter your way through, and learn and absorb and observe and collaborate, like you said, even across generations. This is all cumulative knowledge that was set in motion as far back as Steno. He was a Danish scientist in the 1600s, and he's the one who first was sort of bold enough to say, "Wait a minute. These – " He was finding these big shark teeth.
People were finding fossilized shark teeth, but they didn't know they were fossils. There was no such thing as fossils. And he's the one – Some fisherman called him down to look at a great white shark that they had caught and brought to shore. And he looked at the teeth, and he thought, "Wait a minute. These are – These look just like these tongue-stones that we find in the rocks." And so all the way from Steno this has been cumulative knowledge as people learn more and we have new tools for understanding.
It's really – It's a big pyramid of people who contribute to the science. And it's scientists and lay people amateur fossilists and everything, so it's a big group effort, science is.
Mirsky: And in the last – really in the last 10, 15 years, the scientists who've been working on it who are still alive, some of them, have been fortunate enough to get a really good handle on what was going on with this creature, and why those squid and the Helicoprion were found in the same layers. Because this device that evolution cobbled together, this perpendicular saw in the shark's mouth – and we'll talk about whether or not it was really a shark in a minute, but – it's perfect for squid.
It's perfect for grabbing and eating squid, and it's also, as one of the scientists you quote in the book, says, it's almost like a snail fork for creatures with shells.
Ewing: Yes, exactly. So can imagine if you've seen ammonites, so you've got this shelled cephalopod, so a shelled animal with tentacles out the back of it like an octopus. So those guys, they swim through jet propulsion, so they're swimming, swimming, swimming away from a Helicoprion, and the Helicoprion is chasing, chasing, chasing. And so the cephalopods, they have their tentacles hanging out of the back, swimming away. And so we can imagine that Helicoprion would swim up on one and grab the tentacles.
And so the teeth in the whorl, the tooth crowns, they would snag those tentacles, and Helicoprion would bite down. And the teeth would drag the cephalopod out of its shell, sort of like you stick a fork in a escargot that you get at a restaurant – you stick in and just pluck it out. That's what they think that Helicoprion – one of the ways that it used its whorl.
Mirsky: But Helicoprion discovered that it had become so specialized that when something happened – let's assume for the sake of argument that the food supply diminished, but there could've been other reasons, as you point out in the book – it's stuck. It's in an evolutionary cul-de-sac at this point. It can't go back to trying to feed on anything else.
Ewing: Right. It was so highly specialized – that tremendous specialization of the tooth whorl probably both made it very successful and also led to its eventual extinction. So when the prey base was really strong – this is what people are thinking – but so the prey base was really strong; Helicoprion was the king, apex predator of the day of the middle Permian, and it just ate its way to the top of the food chain.
But then, if something – if there was a little wobble in planetary conditions, and something happened to the prey base, it couldn't – It wasn't like a coyote or something that could scavenge or hunt, or a raven – these great animals that can survive anywhere. It was too specialized. And so they think that that's why it eventually went extinct. And Helicoprion lived during the middle of the Permian, and a lot of people know that at the end of the Permian period, there was the biggest extinction that the planet has known yet.
But as far as scientists know, Helicoprion was not – its extinction was not related to the great end-Permian extinction. It just had its day, and then it was gone.
Mirsky: And as far as we know, no other organism has tried to repeat this evolutionary experiment and come up with the vertical teeth.
Ewing: That's right. There are a group of chondrichthyan fish, cartilaginous fish, with sort of central tooth plates in their mouths, but they're tooth plates, so they're not like Helicoprion's tooth whorl at all. Not even close.
Mirsky: Let's talk about – Because we're gonna have purists who say, "It's not a shark." And according to our 21st century taxonomical classifications, no, it's technically not a shark. We admit that. Although Shark Week itself, on – what is it, the Discovery Channel?
Ewing: Yep. Starts this Sunday.
Mirsky: Right. They have done programs about this animal during Shark Week. So for them, it's close enough, because boy, it sure would've looked like a shark. And as you point out in the book, what the ecological matrix is today, is sufficiently different from what it was 270 million years ago that this thing was, for all intents and purposes back then, a shark.
Ewing: Right. That's right. Helicoprion passes the shark gestalt test. It was big. It was bigger – twice the size of a great white shark. It was a big animal. It was the apex predator. It had these big teeth, or tooth crowns if you wanna get technical. And it had a shark-like tail, they think – they don't know that for sure. But it behaved like a shark. And at that time the group of chondrichthyans – and chondrichthyans are just the cartilaginous fish –
chondrichthyans split off from the bony fish over 400 million years ago, and there's an argument on whether the chondrichthyans split off from the bony fish, or the bony fish might've split off from the chondrichthyans. Anyway, it happened like 400-plus years ago. So the branches split off then. That's why sharks are so "other." We humans come from bony fish a long time ago, and so we're just having no relation to sharks. They're just "the other."
And so the group that is now the true sharks was in the minority in Paleozoic times, before the Permian extinction. What we know now is true sharks, like the great white sharks and mako sharks and thresher sharks, they were the minority before the Permian extinction. And the other group of cartilaginous fish, chondrichthyans, which are the subclass holocephalan, they were the major group at that time. And they were incredibly diverse, far more diverse than what sharks are today.
And they came in all shapes and sizes, all kinds of teeth, all kinds of habitats, all kinds of behaviors. And scientists know a fair amount about these early chondrichthyans because there's a couple of really incredible fossil deposits that reveal great fossils about them. But anyway, so because of the way Helicoprion's jaws were attached to its skull, it technically is not a true shark, and it is not in the lineage that became the true sharks.
It is in the lineage that eventually became the ratfish, which are these weird little creatures that are – there's just not very many of 'em today. There's like over a thousand species of true sharks today, and only 40 species remaining of these holocephalans, or what we call ratfish. And it's all about jaw attachment, which is really technical. But anyway, that was a long time ago, and so I feel, right, the purists really don't like us to call Helicoprion a shark, but it's really hard not to call it a shark, because it looked like a shark.
Mirsky: And the title of the book is Resurrecting the Shark, because what were you gonna call it? Resurrecting the It's-Not-Really-a-Ratfish"? [Laughter]
Ewing: Right, exactly. Resurrecting the Holocephalan. I know, and I had this conversation with a number of people, and it just – I just had to sorta grit my teeth and go, "Well, okay." It's gonna be the one thing that the scientists are really gonna not like very much.
Mirsky: If Linnaeus was swimming around 270 million years ago, he probably would've said, "That's a shark."
Ewing: I think he would've. I definitely think he would. It's like, "If it quacks like a duck – "
Ewing: You have to [laughter] call it as you see it.
Mirsky: So let's talk about Ray Troll, because he is such a central figure to the book. And he's not technically a scientist, but it was really his vision and his energy that kept a lot of this research going, and created a fraternity of researchers who were working on this.
Ewing: Yeah. Ray ran across a Helicoprion fossil in the '90s, and he became obsessed by it. And he just – As an artist. And he was working on a book about ancient sea life, and so he was interested in these things anyway. And plus, as a visual artist, he saw that spiral, and then saw the teeth, and he just was gobsmacked by it. And it became a true obsession for him, and –
Mirsky: And tell everybody about probably his most famous work, which I didn't even realize I had hanging in my house for the last 20 years.
Ewing: Right. The piece that really put Ray on the map initially was originally a tee-shirt, and it was called "Spawn Till You Die." And it has a skull with a salmon sorta crossbones, so it looks like a human skull with salmon crossbones, and little pink naked people all the way around it. And he supported his family in the early days by creating these crazy, punny tee-shirts and posters, like "Bass-Ackwards," and –
I can't remember some of the other ones, but usually involving bars and fish, or crazy things, but that's how Ray was supporting his family in the early days.
Mirsky: Yeah, and I read this in your book. I said, "Wait a minute. I have that. I have that "Spawn Till You Die" on a postcard that somebody sent me a long time ago, and I dredged it up, and so there it was. And so people may be familiar with that example of his work. So go on and tell us more about how he became the Helicoprion wrangler.
Ewing: Yeah. So after he saw that fossil in the LA County Museum basement – someone showed it to him; a paleontologist was taking him on a tour of the museum and showed it to him. And he said, "Y'know," he said, "this tooth whorl, it belonged to an ancient shark called Helicoprion, but nobody knows really very much about it, and you never see it in museum exhibits, because nobody knows really how to reconstruct it.
You can't really put it in a picture, because nobody knows where the whorl fits." And so Ray, he just glommed onto it, and he started – He wanted to draw it. It was a monster in his mind, and he loved weird, ancient monsters, and this weird, ancient shark-y thing just grabbed his imagination. And so he started trying to find information about it, and the paleontologist who originally showed it to him suggested that he talk to a retired paleontologist named Rainer Zangerl, who had worked at the field museum.
And Zangerl wrote the Handbook of Paleoicthyology, the volume on Chondrichthyes, so the ancient cartilaginous fish that includes sharks and skates and rays and ratfish. And so Ray called Rainer, and Rainer sort of took him under his wing. He was a Swiss immigrant. And so he helped Ray kind of get started. And then – But Rainer wasn't really an expert on Helicoprion and so Ray found his way to a Danish paleontologist, Sven Bendix Omgreen.
And Ray called – He picks up the phone and just cold-calls these scientists. He called Bendix Omgreen, who was at dinner in Copenhagen one night, and said, "Hey, [laughter] I'm really curious about these animals, and I happened to see a paper you wrote in the '60." And Rainer and Bendix Omgreen were retired and elderly men by then, but Ray did correspond with both of them. And Rainer bit more – a little more encouraging, I think, than Bendix Omgreen.
Bendix Omgreen just said, "You can't draw this animal because you don't know enough about this animal." And Ray's like, "Yeah, but I wanna draw it!" But both of those men eventually died, within about a year of each other. And so then Ray was sort of left with nobody, no scholars who had been pursuing the study of Helicoprion. So he kind of kept the – he kept the flame going. And Ray became really the repository of information about Helicoprion.
He had assembled all the papers that had been written, and he sort of had a mental inventory of where the fossils were, and in what collections. But no one had been interested for a long time, and so he had kind of moved on to other things. And that's when, in 2010, Jesse Pruitt, an undergraduate at Idaho State University, called him out of the blue because he had seen a fossil in the museum at the Idaho Natural History Museum.
And somebody said, "Well, you should call. You should call that Ray Troll. I think he'd know something about that." So that's sort of the spark that led to this most recent scientific breakthroughs from Team Helico.
Mirsky: And the breakthroughs were just how this tooth whorl actually was situated in the mouth. How it was situated so that it would work. 'Cause it was understood that it was vertical, but people didn't really understand how it could be affixed so that it was functional.
Ewing: Right, right. And actually, so Jesse was looking for an undergraduate research project, and that's how he came to talk to Ray. And Ray suggested to Jesse that Jesse call – just like Ray had done – call the experts in the field. There are about three of them. And so Jesse did call those experts, and the first one that he talked to said, "You're not gonna learn anything new about this animal. You're sort of wasting everybody's time."
And the second person that he called said, "Well, yes, there's really not much more to learn until we find new fossils." But then the third person that he called, who was Michael Coates at the University of Chicago, said, "Really, the key to learning more about this animal is to find something other than teeth." Because chondrichthyans, they don't fossilize well because they're not bony, so they don't leave fossils like dinosaurs do.
So Michael Coates said to Jesse, "You know, there's stuff you can do, but nobody's really gonna advance Helicoprion science until you find something other than teeth." Well, as it turned out, in Bendix Omgreen's 1966 paper, he had studied one of the Idaho fossils, and it looked to him like the rock might contain fossilized jaw material. And so – But nobody connected the dots until Ray and Jesse were talking on the phone, and Ray said, "You should look for Idaho IV, because Bendix Omgreen – "
that was the name of the fossil, Idaho IV – "You should look for that fossil, Idaho IV, because Bendix Omgreen in his 1966 paper said he thought there might be fossilized jaw material in there." But it didn't do Bendix Omgreen any good at that time because the technology wasn't available to peer into the rocks. But voila, here we are, 2010. We have CT scanning machines, and really powerful CT scanning machines that they use for industrial purposes, that really can look through that rock.
So Jesse and _____ ran down and found Idaho IV, and they're like, "Oh, my God, we do have this!" And so they were able to find some money – they were on like a undergraduate research budget, which is nothing, but they were able to find some money and take the fossil to Texas to a special fossil scanning facility. And they scanned the fossil, and by golly, there was jaw material in there, which is what their paper really hinged on. It was the first time – It was what Michael Coates had been talking about.
It was the first time anyone had been able to identify and reveal fossilized material related to Helicoprion other than teeth. And it showed the impression of the whorl in place in the jaw. And so they were able to finally say, for the first time in a hundred years, "Okay, this is it. This is how it worked. This is where it fit." So that was the big splash of their work.
Mirsky: And there's a lot of detail that we won't go into, but it's really just the basically two months of examining each individual image of the CAT scan, and by hand showing some of the contrasts more clearly, so that the image would really be explanatory. Because the background material and the stuff that they were interested in was so close in density that the CAT scan wasn't by itself doing a good enough job of differentiating them. So it's just –
It was an amazing story of just persistence, and stubbornness, and curiosity. And it's just great. And what I really liked about the book was the illustration of how science gets done sometimes. It's this massive, undifferentiated group effort that then sort of comes together when enough people have stumbled onto – or not stumbled, but actually were looking for, the clues that make it possible to actually make the discovery. It's an amazing story.
Ewing: Right, and they're actually was a lot of stumbling onto things. That was one of the things I loved about this story. There's so much serendipity, and so much kind of stumbling around, until – Like somebody stumbles, and then somebody really looks. And I love that about the story, and the sort of outsider science. I mean, the people that did this work, they weren't even vertebrate paleontologist, all of 'em. Invertebrate paleontologists, and an undergraduate student, and an artist, and a biologist.
And they were just driven by their passion and their curiosity – and you hit it right on the head, their stubbornness. And it was just so fun, and so wild to track these folks. And one of the things I love about the story, too, what I found so interesting, is that Helicoprions animal – From the discovery of the first fossil in the late 1880s in Australia through 2013, through this work, we can use this one animal to really track the changing nature of scientific inquiry. The tools have changed. The attitudes have changed.
The people have changed. The processes have changed. What we know has changed. And so it's really cool to be able to use this animal to track that changing nature of scientific inquiry, and also the science in the context of history – American history and Russian history and European history. It's just such a great, rich story. I felt so lucky to be able to try to tell it.
Mirsky: That's it for this episode. Get your science news at our website, www.scientificamerican.com, where you can also check out the article titled, Forget Sharks: Seven Things in the Water Swimmers should Actually Fear – It's the Microbes That Should Scare You. And follow us on Twitter, where you'll get a tweet whenever a new item hits the website. Our Twitter name is @sciam. For Scientific American's Science Talk, I'm Steve Mirsky. Thanks for clicking on us.
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