Bright Ideas host Stephen Smith talks Titanosauria with dinosaur expert Kristi Curry Rogers. Rogers conducts field research in Montana, Madagascar, and Zimbabwe and teaches at Macalester College in St. Paul. They talk about dinosaur bones, why some of sauropods got smaller as they evolved and how she reconstructs the lives of these long extinct creatures.
About the guest:
Kristi Curry Rogers is a vertebrate paleontologist most interested in the evolutionary history and paleobiology of dinosaurs.
She is most deeply invested in understanding the long-necked, herbivorous dinosaurs known as sauropods. This group existed for more than 160 million years, was globally distributed, and included the largest terrestrial vertebrates of all time. As such they are perfect fodder for her interest in dinosaur evolution and offer a wealth of data on the biological consequences of living life at large size.
Stephen Smith: From MPR News Presents, this is Bright Ideas, Fresh Thoughts on Big Issues. I'm Stephen Smith. Each month, I invite a guest to the forum here at Minnesota Public Radio headquarters to talk about important issues and ideas before a live audience. My guest this time is Kristi Curry Rogers, a professor at Macalester College who studies the most mammoth monsters ever to walk the Earth, the aptly name Titanosaurs. These are relatives of the classic long necked dinosaurs you see in many museums and on the occasional Sinclair Gas Station sign.
Kristi Curry Rogers is on the Smithsonian Institution's list of who's who in paleontology. She made a big discovery while she was still in graduate school, and she's here to talk with us now about what's new in the world of dinosaurs, what it's like for women in science these days, and why we should care about creatures that lived and died more than 65 million years ago. Please welcome Kristi Curry Rogers.
Smith: First of all, let's talk about dinosaurs. I think that lots of us have a vague idea of what a dinosaur is. We probably have a lot of ideas about a dinosaur isn't. Why don't you start off by telling us what a dino is? And some of the things that it's not that people think it is.
Kristi Curry Rogers: I think the easiest way to think about what a dinosaur is sometimes is to think about what a dinosaur is not. Most of us in the audience have probably gotten a tube of dinosaur toys at some point in our lives that include things like sail backed reptiles, and wooly mammoths, and flying reptiles, and swimming reptiles. None of those things are dinosaurs, even though they come in the tubes. Dinosaurs are a group of reptiles that are very specialized. They have a bunch of different characteristics of their skeletons that tell us that they were adapted for running. They had grasping hands, they have mobile jaws. They have really stable hips. Most of the things you could identify a dinosaur on the basis are things that you see on the insides.
If you could imagine dissecting a whale, all of the skin and muscles. In fact, when dinosaurs first show up on the planet, you wouldn't recognize one as anything different or anything special if it ran by you. You'd really have to dissect all of the parts away to identify it accurately.
But you all probably know what dinosaurs are. If you imagine the diversity of dinosaur groups, there are big meat eating dinosaurs, and small meat eating dinosaurs, feathered meat eating dinosaurs. There are horned dinosaurs and frilled dinosaurs, and spiked dinosaurs, and long necked dinosaurs, and duck billed dinosaurs, and bone headed dinosaurs.
All of those things are dinosaurs.
Smith: So if we have a bunch of stuff running past us, we'll have some non dinosaurs running past us at the same time that there are dinosaurs.
Rogers: That's right.
Smith: Why do you make a distinction between a group of things called dinosaurs and all of that other old stuff that was running around and was also spiky and scary looking?
Rogers: When we think about dinosaurs, we like to think about how they relate to other organisms in terms of evolution and other organisms living on the Earth at the same time, and other organisms even living on the Earth now. With dinosaurs, there are these key characteristics that we call diagnostic characteristics. They diagnose a dinosaur as something unique, especially these running legs. If you look at a reptile, a normal reptile, how do its limbs look to you? They're sprawled out, right? They have their bellies kind of hanging in between their limbs. Dinosaurs pull their limbs under their bodies so that they can run. Running is one of the primary features that separates dinosaurs from all other reptiles. It makes them something a little bit different.
If you look really closely at dinosaur biology, especially during the course of their evolutionary history, what we see is that they also show another set of unique adaptations. For example, they grow much, much faster than any living reptile does. The largest dinosaurs grow faster by an order of you know, 50 times faster than any living reptile. The small body dinosaurs grow maybe only one or two times faster than any living reptile, but all dinosaurs grow really fast.
When you look at these kinds of characteristics, you begin to see a reptile group that is not very much like reptiles in anything except their scaly skin. They're worth defining as a unique group, because they have unique characteristics.
Smith: This is a silly question, but did they have to grow really fast to get really big relative to the other reptiles?
Rogers: We always think about why dinosaurs got big, and the real reason is just because they could. They could eat as much as they wanted. Most dinosaurs, especially these long necked dinosaurs that I like to work on the most, they probably ate almost all the time, because they were fueling these incredibly fast growth rates. Their growth was as fast as a modern whale's. Whales grow to their full adult size in about two years. Imagine a dinosaur growing from an egg. No, hatching from an egg no bigger than the size of a grapefruit and growing from something that may be a foot or two long from head to tail at birth to being 75 feet long from head to tail in about 10 or 12 years. That's pretty insane growth rate.
Smith: All right. Dinosaurs lived when?
Rogers: They evolved around 230 million years ago, that's their first occurrence in the fossil record, although they probably appeared on Earth a little before then. They were only lucky enough to get preserved slightly after that. They went extinct, at least some of them did, 65 million years ago. Most paleontologists now understand that the birds living in our backyards are actually dinosaurs, just specialized dinosaurs with no teeth, no bony tails and feathers. In some cases, like for me, I think that dinosaurs are still with us, that they haven't gone extinct at all.
Smith: We'll talk about that in a little bit, because that's actually I think still a bit of a controversial subject. The dinosaurs that we think of I think most commonly are, I would guess, the big ferocious Tyrannosaurus Rex kind of dinosaur maybe, and then the kind that you like to study more, the long necked vegetarian... Long necked, big, bulky body, long, spindly...
Rogers: The gentle giants.
Smith: The gentle giant. OK. You know, why did you choose to study the gentle giant instead of the scary guy?
Rogers: I came across sauropods when I was an undergraduate. I see there are some kids in the audience, and maybe some of the kids in the audience want to be paleontologists when they grow up. I was that kind of kid, and from the time I was really young, I was really interested in long necked dinosaurs. They were like incredible monsters to me. I could not understand, even as a child, how anything that big could walk on land. I was really curious about them. They were the only dinosaurs that I actually cared all that much about as a child. I was into invertebrate fossils and then seashells.
Smith: How did you encounter them? Was it on television? Was it on the Sinclair sign, on the gas station?
Rogers: It was in a Weekly Reader. I was in second grade. I still have it, it's embarrassing, but I read it, and there was a cover story on a dinosaur egg in Baby's Sight, discovered in Montana. Though the dinosaurs found, there were duck billed dinosaurs, the picture on the front of the weekly reader had baby long necked dinosaurs hatching out of eggs.
Smith: Well, that's really good that in that case, they weren't accurate you know, because they got you hooked.
Rogers: I know, they got me hooked. I thought they were adorable. [laughs] I really wanted to know how they could go from being so tiny to so big. Oddly enough, that's what I've spent most of my career working on, is exactly how dinosaurs could go from being so tiny to so big in such a rapid way. Sauropods have just always been the dinosaur group that sparked my interest. When I was in grad school, I was on a dinosaur dig in Madagascar, and the dinosaurs that we were finding the most commonly were the sauropods. No one else in our group really cared about them; they were all into the meat eating dinosaurs.
That was the thing for all of the other paleontologists, crocodiles and meat eaters, and birds. I thought sauropods were really cool, so I did that for my dissertation research.
Smith: This was what, before vegetarianism and veganism got really popular in the United States?
Rogers: Oh no. I'm not that old, come on. [laughter]
Smith: One of the things that has always challenged me as a person who's interested in dinosaurs but never got hooked are the names, so I'm going to ask you to talk about some of the names and I even want to talk about how they come about. But a sauropod, this is the group within the dinosaurs that you specialize in or the big group. What does sauropod mean? It has something to do with foot.
Rogers: Sauropod means lizard foot.
Smith: Lizard foot.
Rogers: Yes. So sauropods have five fingers and five toes, so they have traditional lizard like feet. They have very basic reptile sorts of feet. So when they were first discovered, they had big claws on their feet. When they were first discovered back in the 1800s, the first person that named this large group called them the lizard foot dinosaurs in contrast to the meat eating dinosaurs that are known as the theropods. Theropod means beast foot. Theropods have bird like feet with three toes and very sharp claws.
Smith: So it really comes out of what was found and it's feet first.
Rogers: Feet first and how those things are similar to those things we can look at right now in our environment. So paleontologists are famous comparative anatomists. We spend most of our time thinking about how what we find relates to things that we can observe right now because dinosaurs are mythical in some ways. We only have little bits of them to go on in most cases. And even though we really have a complete skeleton, we might only have one or two.
And so we really have to look at modern animals that relate to them in some way whether it's just a shared anatomy or a shared set of relationships so we can understand the dinosaurs. So a lot of our names are derived from anatomical features that are recognizable.
Smith: And hopefully it seems like some of the names come from Latin and some of them come from Greek.
Rogers: That's true.
Smith: That really makes a lot of sense. How did that come about? [laughter]
Rogers: That is the language of classification, right? So that's the lexicon of classification. It was established in the 1700s by a guy named Linnaeus. You might remember this from your biology classes in high school or college. Linnaeus was so into naming and classification that he Latinized his own name. So his name was Carl Linnaeus. He was a Swedish taxonomist and he changed his name to Carolus Linnaus because he wanted to classify himself.
Smith: That worked out well for him.
Rogers: It did. [laughs]
Smith: As a guy who's name is Stephen Smith, I might want to try that on sometime.
Rogers: Maybe so. It will give you a little uniqueness.
Smith: But why the mix of one language and the other?
Rogers: It's just a technicality for no particular reason at all. And in fact, a lot of dinosaur names these days aren't based on Latin or Greek. They're based on Malagasy, or German or San. They're based on any language you can imagine. They're based on a lot of the languages in the countries from which dinosaurs are being discovered or being employed in the naming so that people in those countries can have a name recognition with the animal that we're describing.
Smith: Let's talk about the dinosaur that you had a big part in discovering when you were in graduate school. This was in Madagascar and you folks were digging around one day.
Rogers: We had been going to Madagascar for a number of years and our project started because one of my advisors at Stony Brook was mammal paleontologist and the endemic or modern fauna in Madagascar is very weird. You guys are probably familiar with lemurs, and chameleons and pigmy hippopotami. A lot of these animals are not found anywhere else in the world so for a mammal paleontologist, people really wanted to find out where the ancestors of Madagascar's fauna came from. Where did the ancestors of these weird organisms come from?
And so my advisor was a mammal paleontologist with just this interest and so he decided that he would go to Madagascar to the only place that was known to have ancient fossils, fossils that were older than 15,000 years old, and that happened to be a cretaceous bed.
Smith: A cretaceous bed? Meaning from a particular period of time?
Rogers: Right. Meaning sometime between 120 million years and 65 million years ago. And so he went in search specifically in this little time period to look for mammal fossils. And the reason he knew about this is because there was a report in the 1890s by a French paleontologist recording a bunch of dinosaur bones. They weren't many mammal bones in these bones that were described in the 1890s, just dinosaurs. But my friend Dave thought, "Maybe I could find some mammals there. I'm good at finding mammal teeth. They're tiny, but I can find them."
So he had been running these field seasons in search of mammals and they hadn't found anything, nothing to speak of, just a couple of small fragments of what might have been mammal teeth. And when I started at Stony Brook University as a graduate student, one of the first things I got to do was go to Madagascar. We spent our summer digging up these long neck dinosaurs.
Smith: And throwing them away because that's not what your guy was looking for. "Ah! I don't want this!" [laughter]
Rogers: He was actually complaining a lot about the fact that it would be really nice to find something that he could bring home in his pocket.
Smith: "Oh no, another massive neck!"
Rogers: And not another dinosaur. Because these dinosaurs as you can imagine, they take an entire summer. One dinosaur could take an entire summer or maybe even two summers to excavate because they're 50 feet long to 100 feet long from head to tail. Their femoral, their thigh bones, are bigger than me. And so these are enormous animals that take forever to dig up. Nobody likes them except for me. I'm like the world's smallest paleontologist and I work on the world's largest dinosaurs. [laughter]
Rogers: But I decided. We were sitting in this quarry and I had been toying around with my PhD idea and what I wanted to do. I knew I wanted to work on a group of enigmatic dinosaurs that no one else is working on.
Smith: Enigmatic, is that a scientific term or does it just mean that they're mysterious?
Rogers: [laughs] Just mysterious. This is how you go about choosing a dissertation project. I knew I wanted to work on a group of poorly understood dinosaurs. I knew I wanted to work on a group of dinosaurs that were globally distributed because if they're globally distributed, then you get to travel the world to museums to study their bones and dig them up. So I knew I wanted to do those two things. And I knew I wanted to employ some new methods that I had not employed when I was an undergraduate student working on dinosaur questions.
And so I had been thinking of a group of very basal dinosaurs that are called the post sauropods. They're some of the first dinosaurs on Earth.
Smith: A basal dinosaur?
Rogers: Just some of the dinosaurs that are unspecialized in their anatomy. They're at the bottom of the dinosaur family tree.
Smith: The humble dinosaur.
Rogers: So it's hard to tell whether they're meat eaters, or plant eaters or something in between. They're very controversial. They're very simple. And so because of that, they're hard to study.
Smith: How can they be controversial? They're just minding their own business, lying in the dirt. How can they be controversial?
Rogers: Paleontologists find a lot of controversy in these animals. We can get into fist fights at professional meetings about whether or not we're right about our dinosaur questions. [laughter]
Rogers: So anyway I decided that sitting in this hot quarry and spending all of my time digging up a single limb bone that these were the animals that I wanted to study for the rest of my life. So I decided then and there that I was going to do my dissertation on the titanosaurs which had all of the right characteristics. They're globally distributed. They're found all over the world, even in Antarctica. They're really hard to understand because their fossil record is not very clear. We don't have complete skeletons for very many of them.
And they're interesting because they evolved at a time when the continents were all together but as the continents split apart, they drifted with the continents and thus diversified over time. And so they're a really nice evolutionary story and one that I thought would be an interesting one to work on for my PhD.
Smith: Going back to the names. You got to be part of the naming of this particular titanosaur that you found. Is that right?
Rogers: That's right.
Smith: And one reason it was super cool is that you found the whole thing.
Rogers: This is the first time for one of these dinosaurs that we had the head and the body. For most of them, you might find a single vertebra, or a few limb bones or skull, but nothing else. And so this was the first occurrence of one of these dinosaurs with a head, and a vertebral column, and limbs, and pelvic girdles and pectoral girdles; all of the body parts there. So it was pretty exciting because it was the first time.
Once you have something like that which is pretty complete, you can compare everything else to it so it serves as a touchstone of all of the other ambiguous organisms all over the world. So that was cool. And it's also just a really beautiful skeleton. It's really well preserved, so we had a lot that we could say about it's anatomy in a lot of detail.
Smith: So what did you call it?
Rogers: We called it rapetosaurus krausei. Unfortantely the name looks like "rape to saurus." Sorry. [laughter]
Smith: Did you guys write it out before you thought up the name?
Smith: Well, that's good. What does it mean?
Rogers: We asked our Malagasy colleagues to help out with the name because like I said before, we wanted something that would be recognizable to the Malagasy people in the field or where we were working.
Smith: The folks in Madagascar?
Rogers: That's right. And they said that there were two giant mythical creatures in their folklore. One was called Darfefe and we thought it sounded too much like a poodle's name and then also according to these guys who were working with us, there was a bad giant. The giant that killed people and ate children. It wasn't a giant that you would really want to see walking by and have some kind of affiliation with.
So we asked them about the other giant and the other giant was called Rapeto. It was just a mischievous giant who would just do things like step on a house by accident, but it wasn't doing anything bad on purpose. And so we named the dinosaur rapetosaurus which means the mischievous giant lizard from Madagascar for its first name. And then the second name, the species name is krausei which was the name of the mammal paleontologist, one of my advisors, who started the project in Madagascar and had yet to find a mammal fossil. So we thought we would give him a dinosaur which is a really crafty thing to do just before your PhD defense.
Smith: Especially when your advisor is grumpy about that. When do we find the first description of people encountering what we know are dinosaur remains or fossils in the human literature, if you will?
Rogers: There are dinosaur bones recorded, I think, from the 1500s or 1600s, just a few pictures and the first named dinosaurs were really named in 1842 by Sir Richard Owen who is the guy who coined the term dinosauria. Of course Native American people and Mongolians were finding dinosaur fossils in their landscapes all the time and they have very specific legends associated with the bones that they were finding, so it's not as though non western people were not finding dinosaur bones. They were. They just interpreted them a little bit differently than the western paleontologists did a little bit later on.
Smith: But westerners, if I remember correctly, really didn't figure out what these critters were until well into the 1800s.
Rogers: It was really about the middle 1800s before anybody recognized them as large reptiles, so 1842 is the first naming of this group that included three very different kinds of dinosaurs; a plated dinosaur, a meat eating dinosaur and a kind of duck billed dinosaur. And those three dinosaurs were unified within this group of large bodied reptiles. And I think you mentioned at the beginning, dinosaur means terribly great or fearfully great reptile. And so that was homage to how big these reptiles were. Not how scary they were, but how big they were.
Smith: Now the really big one that you work on, the big ones you work on that are vegetarian, you say that they kind of ate all of the time. Could that be part of the reason that they didn't survive was that they...? One of the challenges as I understand it in studying these dinosaurs is how they could be so big and how they could function at that size. At one time I think it was thought that maybe some of these sauropods if their head was up too high, they'd faint.
Rogers: The thing that I like to think about sauropods as a group of animals is that they are really aliens. They are really bizarre animals. They do not seem that they are well suited for any sort of life anywhere; terrestrial or in water. They just seem bizarre.
Smith: In fact, I think people thought they lived in water. Scientists thought they had to have lived in water to support the size of their girth.
Rogers: That's right. Some people still argue that they spent most of their time in water. But when you really start looking at their bones carefully, what you see is sort of a marvel of engineering. They have big, thick columnar limbs that are perfectly suited just like gothic columns for holding up massive weights. Their necks are filled with air so that their necks even though they are very, very long, they would have been very light.
And if you take into account all of the air spaces in their necks and heads, you can actually decrease the body mass estimates for these animals by about 10% to 20%. So their bodies are filled with air rather than being filled with tissue, so they are very light weight animals in spite of their huge size.
Smith: These particular animals, their necks were so long like a giraffes so they could reach up high and get the stuff that others couldn't?
Rogers: It's an old idea that their necks were well adapted for feeding at the tops of trees and in pretty recent years, people have been working on modeling their neck vertebrae with computers to try to see how the vertebrae could articulate. Whether they could raise their necks up high like a brachiosaurus, the giraffe like dinosaur that some of you are probably familiar with, or whether they kept their necks straight out in front of them more horizontally. And it turns out that most of these dinosaurs probably used their long necks not to reach the top of the trees, but to reach more broadly from the middle ranges of trees and from the ground.
Smith: Without having to move?
Rogers: Without having to move, so to eat as much as they could from their landscape without having to move their limbs at all. [laughs]
Smith: A really stretched out cow! [laughter]
Rogers: It's really true. There are a couple of excellent fossils of titanosaur feces, fossilized poop, and if you look at that under a microscope, you can see that there are grass fossils and plant fossils from the middles of trees, berries, sticks. These animals were eating everything that they could, but not necessarily from the tops of the trees. And if you think about where fruit is, it's not at the tops of the trees. It's somewhere in the middle.
Smith: How did science figure out that their necks were filled with air?
Rogers: So they have these unusual spaces. If we could take a CT Scan just like we would take a CT Scan of one of us if we were sick, you can take a CT Scan of a vertebrae of one of these dinosaurs and see the bone and see the spaces inside of the bone. Those spaces are actually just filled with air. They have these diverticula, these little special sacs of their lungs like a bird does that infiltrate all of their vertebrae and sometimes some of their limb bones, some of their pelvic bones.
Some people think that those special sacs may have actually had lung tissue in them that might have helped sauropods breathe like birds, breathe in a very efficient way without leaving any dead airspace. When we breathe in and we breathe out, we leave a lot of dead air in our lungs that we never actually extract the oxygen very effectively from. We're not very efficient warm blooded animals.
Birds have totally trumped us on that. They can breathe in, and breathe in and breathe in and extract every little bit of oxygen from that single set of breaths that they take. And so because of that we think dinosaurs, especially the meat eating dinosaurs and the long necked dinosaurs who are both more closely related to birds than any other dinosaur groups, we think that both of those animals also had that kind of specialization of their lungs so that they infiltrated their bones with air sacs to lighten the load and also help them breathe more efficiently.
Smith: We were talking about the dinosaur that you had a big part in discovering in Madagascar. What do you do to top yourself when you've been part of discovering an entire new critter like that?
Rogers: I don't know. Then you have to try to understand it. Naming a dinosaur is actually not that hard. Don't let people fool you into thinking that it is. When you search for dinosaurs in a new place and you find them, then you have to give them a name so that everyone can talk about them and that's not very difficult to do. It's describing the anatomy. I think the harder thing to do is to really understand what they were doing when they were alive. And so trying to write great papers and train really smart students how to carry on that tradition is what I think is the most important thing.
Smith: And where is your dinosaur at the moment? Where's the skeleton?
Rogers: The skeleton is at the Field Museum of Natural History in Chicago. It's mounted in an exhibit there called "Life Over Time," I think so you guys can check it out, or maybe it's called "The Evolving Planet" exhibit. I think they keep changing it, but it's a dinosaur mounted in their exhibit and most of the other bones of that named dinosaur's friends are all held in the collection there. [laughs]
Smith: How did it end up there? Did the field sponsor the research?
Rogers: No. We had an arrangement so that when we worked in Madagascar, we had to make a deal with a museum to take any of the bones that we found. It's important that the bones are held in a proper museum where they can be prepared and curated and there isn't a museum of that sort in Madagascar. So the Field Museum basically has all of these bones on long term loan from Madagascar and eventually the bones will go back to Madagascar.
Some of the researchers on our team worked at the Field Museum when the project began, but none of them work there now so the Field Museum unfortunately just keeps amassing our bones over time. They're stuck with us at this point.
Smith: Do different museums have relationships with different parts of the globe, for example the Science Museum of Minnesota, the Natural History Museum in New York?
Rogers: Most museums are driven by the scientists who are curating their collection and so in terms of collecting, most museums are really working with the scientists. So they'll bring in bones from scientists working in different areas.
At the American Museum in New York, they have a lot of bones from Mongolia because Mongolia was a real hot bed for them in the 1920s and they've been going back to Mongolia. Now Mongolia has its own exceptional paleontology program, so there's no need to bring the bones back to New York. They can just go to Mongolia to study them. The Smithsonian has great collections from Africa because the Curator of Dinosaurs there collects things from Africa.
So you work things out with each country that you're working with with particular scientists to get the place that is most carefully kept for those bones so the bones don't get lost in the shuffle along the way.
Smith: Is there a glut of bones? Are there enough places for bones to go with people digging them up?
Rogers: There are plenty. In fact, I was visiting a museum in Berlin just a few years ago and there are bones in the museum in Berlin that were collected in the 1910s and are still sitting on the shelves in the bamboo and mud containers that they were carried out of the field in. They haven't even been opened and prepared because there is such a huge amount of material.
Smith: There is a backlog of bones.
Rogers: Yes. There is seriously a backlog of bones.
Smith: Is that because there aren't enough people who want to study the part of the process that's less glamorous, that's back in the museum instead of you intrepid folks who are out in the field?
Rogers: Museum work tends to be a little bit more boring, right? It's a little more tedious than going out in the field and discovering things although some would argue that sitting out in the hot sun... I know that my colleagues and I have argued this point while we were sitting for days finding nothing, breaking rocks in the hot sun, that you could actually do that in prison and have a shower at the end of the day.
Rogers: People work in museums; it's just that it takes a really long time to do this stuff. It takes a long time to put bones together and clean them up. There are not a ton of people that are really trained at preparing bones, so being a fossil preparator is one of the most critical jobs along the way to studying dinosaurs.
Preparators are really patient, really careful artists who really know how to do it. If you're good at puzzles, it's a great job for you. The preparators that I worked with at the Science Museum in Minnesota are some of the best, most patient people I've ever met. They can put a box of pieces of bones back together into something that's recognizable as anatomy. It's amazing. I would just get frustrated and throw it over my shoulder. [laughs]
Smith: It's been said by many other people that the work you do in some ways is a version of crime scene analysis. That you are looking at something that is dead and you're trying to figure out from what's left behind how it lived and how it died, except the crime scene has been around for a lot longer and it's been rained on and it's been flooded and et cetera. Do you think of it that way?
Rogers: I do. I mostly think of it that way because my husband is the geologist whose science is based on death and burial. He spends all of his time thinking about the dead and how they get into the fossil record. And because of that, you really begin to see what I saw when I started out in this field. I saw the bones just as anatomical specimens that you could put together and imagine the anatomy and the evolution of these organizations and their paleobiology. But when you include that environmental piece, it becomes so much more meaningful. My husband Ray is the geologist who works with our team all around the world and he's...
Smith: Ray Rogers at Macalester College as well.
Rogers: That's right and he's really great at painting that picture for you and recreating that environment so you have a place to put those dinosaurs.
Smith: He's studying the rocks around your bones.
Rogers: He is.
Smith: You also mentioned to me earlier that you are engaged in a real day experiment, a present day experiment that's Paleolithic in its own sense.
Rogers: I'm really irritable today because my comparative vertebrae anatomy class at Macalester and I were all doing the Paleolithic diet this week.
Smith: It's an update on the South Beach Diet.
Rogers: There's no coffee and if you're a vegetarian like I am, there's also no protein. I guess you can have nuts, but there are only so many nuts you can eat in a single day and not feel really hungry at the end of it. [laughs]
Smith: Is your husband doing this at the same time?
Rogers: No. He refuses. [laughter]
Smith: Good to know. In terms of trying to extrapolate from what you find and what the creatures look like, one of the things that puzzles me is how you can know. You can know what the bones look like and you can fill out a form around them, but what about what colors they were and how they sounded?
When we engage in anything from a Hollywood movie to some sort of a well done animation at a legitimate science museum, these are not skeletons walking around and they tend to have audio. Where are the clues to either as to what they look like or what they sounded like?
Rogers: So your real question is, "Why does your dilophosaurus have hearts painted on its side?" [laughs]
Smith: We have two dinosaurs on the table between us. One is a larger sauropod that she has signed and we are going to raffle off at the end of the conversation and the other one is something from my office. It's a meat eating dinosaur that has hearts on it and I can't remember why. I think it was a Valentine's present.
Rogers: So with color, we actually have a lot of interesting data. With feathered dinosaurs... So dinosaurs and birds are very close relatives, they share a common ancestor and there are some dinosaurs that have feathery skin. So for some of those animals, their skin or feathers are so well preserved that you can look at them under an electron scanning microscope and detect the morphology and the shape of the cells and it turns out the cells can tell you something about the actual color of the feather. So for some dinosaurs that have well preserved feathers, we know their feathers were black and white. We know that some of their feathers were orange, rusty colored. And for some of them, we know that their feathers were iridescent black like a crow's feathers. That's really well supported from the fossil record.
For other large dinosaurs like the ones that I work on, their skin coloration is a little harder to pin down. We don't often have skin preserved at that level of detail in these big animals and so we have to use a little bit of bracketing and a little bit of our understanding of modern animals to help us figure it out.
So for example, crocodiles and birds are both members of the group of reptiles called the archosaurs, the ruling reptiles that also included dinosaurs. Dinosaurs are kind of firmly nestled in there between crocodiles and birds. Both crocodiles and birds see in color, and so it makes more sense to an evolutionary biologist that seeing in color evolves one time in that reptile lineage before all three of those organisms split into their divergent groups.
And so we imagine that dinosaurs see in color, and that's fairly well supported by what we see in the fossil records. So dinosaurs could be basically any color that you want them to be. They can be as vivid as a toucan or a parrot, they can be as dull as a crocodile. I'm working on an article right now with "Scientific American", and one of the things that we've been going back and forth with an artist about is how to color the sauropods.
So in his first draft, he made the sauropods look like big elephants. They looked like this dinosaur sitting up here between us, greenish grey, boring looking, not a lot of pretty colors. And we wrote him back and said, "Can you please make them look more like this website filled with lizards, The 20 Most Colorful Lizards on Earth?" Because it's a totally viable hypothesis that dinosaurs were colorful, as colorful as any modern bird.
Smith: And it's a lot more fun.
Rogers: It's certainly more fun and more interesting to look at, don't you think? Colored dinosaurs are much cooler than green ones.
Smith: And what about sound? Is there any science behind the sounds that we hear these creatures usually roaring and bellowing and sounding fearsome, or shrieking in some sort of terrifying and with lots of echo?
Rogers: So there is a way to get at dinosaur sound. We do it in a little bit of a strange way: we CT scan their skulls, and then we look at the shapes of their inner ear canals and the shapes of their inner ear spaces. And in doing that, you can detect something about what sounds they could hear, and then you can reconstruct what frequencies they might have made vocalizations at, if you can get at the frequencies that they could hear. So for example, we know that duckbill dinosaurs heard low rumbling frequencies because of the shape of their inner ears, just like elephants make across a prairie.
Smith: Subsonic, yeah.
Rogers: Yeah, across the savanna now.
Smith: Subsonic for humans.
Rogers: That's right. And other dinosaurs have much higher pitched squeaks and squeals. No dinosaur that we know of growls. That's a specialized trait of mammals. There's no reptile that we know of that growls. Hissing, squealing, squeaking, tweeting, chirping.
Rogers: Roaring is probably not OK with dinosaurs.
Smith: More like a growl.
Rogers: It's more like a low, rumbly, super sort of subsonic low rumble, something that you would feel but not hear.
Smith: You believe, you subscribe to the idea that we actually still have dinosaurs among us.
Rogers: We do.
Smith: And, but not everybody agrees with you, or has it been settled by now?
Rogers: I would say that pretty much all paleontologists with the exception of one. There is one that's holding out.
Smith: Is it like the U.S. Senate, where if there's one person holding out, you just can't move on?
Rogers: We tend to ignore that one guy. But pretty much everyone agrees that the evidence is overwhelming. And it just keeps getting better. We have evidence from behavior, from dinosaurs sitting on nests of eggs, we have evidence from feathers, evidence from dinosaurs that evolve away their teeth and their tails over time. I mean, there are a million things.
There's really excellent evidence coming now from a field of study called evolutionary developmental biology, or evo devo, where people go in and fiddle around with the genetics of dinosaurs birds, sorry and try to see if they can reinvigorate the programs, the fossil genetic programs, within the genomes of modern birds to make them have teeth again like their dinosaur ancestors, and they can. It's really pretty amazing.
Smith: Are there some kinds of birds that are more dinosauric than others? I mean, you would sort of think that maybe the larger, some of the raptors, or maybe the more primitive birds like the loon?
Rogers: Yeah, some of the more primitive birds are probably more closely related to dinosaurs. The ratites, like the ostriches and emus, are fairly closely related to dinosaurs. But all birds, really, all birds come from the same dinosaur precursor, so all birds are sort of they're all dinosaurs, there are just some that are more specialized than others.
Smith: The dinosaur, there was a time, and it wasn't that long ago, when in the popular imagination and this may have been the way that dinosaurs were being described by scientists that dinosaurs were viewed as a symbol of failure, right? They were the things that didn't survive. And that's a boring story, ultimately.
And then somehow, the story got changed, and dinosaurs became hip and cool, and this was before Stephen Spielberg and "Jurassic Park", I believe. What happened in the science did something happen in the science to change from kind of that old, "Here's why they did not make it," to, "Here's what's cool about these guys."
Rogers: There were a series of books that were written when I was a kid in the 80s that fueled a time in the science that we call the Dinosaur Renaissance. And this was the time where all of the old ideas were challenged. So people had really written off dinosaurs as these sort of icons for extinction, failure to adapt to their changing environments, out competed by the sneaky little mammals eating their eggs, you know, take your pick of any crazy scenario.
But in the 1980s, people like Jack Horner from Montana State University, who was the model for the character Alan Grant in Michael Crichton's "Jurassic Park" book, found dinosaur eggs and babies, and all of a sudden, we started thinking about dinosaurs as being caring parents, a thing that we had only really associated ever before with birds and mammals.
A guy named Robert Bakker, who at the time was in Colorado, I think at Colorado State, or maybe at Yale, as a graduate student, wrote a book called "Dinosaur Heresies", in which he basically took to task every single idea that we had about dinosaurs and just said we're wrong, dinosaurs are more like mammals and birds than they are like reptiles, and we need to look at them in a different way.
And those works by those guys and by a guy named John Ostram from Yale who found this very bird like dinosaur called deinonychus in Montana. That was the model for the character velociraptor in "Jurassic Park". Those guys really set the stage for a new breed of scientists who were thinking about dinosaurs and trying to test out the idea that they were more active than we'd imagined before.
And most of the people in the generation right after these writers had written these books were really trying to prove them wrong, trying to show them that dinosaurs were just like everyone had always thought they were, and instead, they kept finding that they were actually right.
Smith: So there was a revision, then a reaction to the revision.
Rogers: That's right.
Smith: And the names that you mentioned, you said, you know, "these guys", this business of dinosaurs and paleontology has been pretty much a man's business, for a long time, anyway. When you started getting into it, were there many women in the field?
Rogers: There was just, there were three.
Smith: And we're talking about a field with more than 10 people in it, I assume.
Rogers: Right. So the Society of Vertebrate Paleontology is our professional society, and there are probably close to 2000, 2,500 members worldwide, and many of those I should say that women are actually, there are a lot of women paleontologists, but many of them work on mammals or plants or invertebrates; very few women work on dinosaurs. And so it's still a fairly male dominated discipline.
One of my friends and I sat down together at our last paleontology meeting and wrote out a list. We were trying to make a list of women that could come and sit on a panel for the women in SVP, to talk to young women in the field about getting jobs. And we were the only ones we could think of, just the two of us.
And so we realized that even though we have this perception that there is a big sea change going on, because there are lots and lots of young women students in our field, that transition doesn't always happen for those young women students to become professionals in the field.
Smith: OK, so why is that, do you think?
Rogers: We thought about it a lot as a group, and I think that it's a difficult field to manage the balance of family life and field work. I think that's the real problem, and it's probably very similar for women who work in any field heavy discipline, because we, you know, I have a nine year old daughter, a nearly nine year old daughter, she'll be nine in April. And for us, my husband's a geologist, we both do field work, and since our daughter's been born, because we do field work in politically unstable places, we usually are gone for six to eight weeks at a time; you can't really bring a baby to a politically unstable, malarial ridden region, you know? It's risky.
Smith: Zimbabwe. Right.
Rogers: And so we take turns. And that's sometimes not ideal. It makes it really difficult. And if you are a woman trying to manage that responsibility, it can be really challenging for people, I think. And some people decide that it's not really worth it to make that choice.
Smith: Is there any institutional resistance to women in the field? Is there a chauvinism there as well, or do you think it really is simply at this point a matter of practicalities?
Rogers: I think in some ways, it's really a matter of practicalities. There have been in the last several years, women have been the president of the Society of Vertebrate Paleontology, three women in the last eight years. So out of four presidents, three of the past four have been women. So I think the field is changing.
I don't think it's hugely resistant to women or anything like that, but I do think it's a hard field to be a woman in, particularly when you have this demand to travel a lot. And my husband and I get around it by taking turns on our international field seasons, and by bringing our daughter with us anywhere we can, so...
Smith: Montana, for example, where you've done a fair amount of...
Rogers: She was in Montana at three months old, in the middle of nowhere. Montana is a far harsher place than you might expect. And she was in Patagonia when she was nine months old on a dinosaur dig where we were camping, you know, camping in a tent for five weeks, and...
Smith: And it's hard to deal with an ear infection when you're way out in the boonies like that.
Rogers: It's really funny, she was the happiest kid I have ever seen and the filthiest baby. I have pictures of her, and I thought, what would my friends back home think of my child? She was covered in drool and mud, you know? But she loved it. I think she's a little jaded about dinosaurs, though. She's not too excited about them.
Smith: "Oh, not them again!" Let's talk a bit more about, once you got captivated by dinosaurs in "The Weekly Reader", you really set a very determined trajectory over time to get yourself to Montana. I wonder if you can describe that story.
Rogers: Sure. So I, second grade, read "The Weekly Reader", decided I wanted to be a paleontologist. I grew up in a very small town in southern Missouri. I asked my dad what fossils were. My dad was a band director, and he said, "I don't know, let's go to the library and look it up." So we went to the library, and I couldn't really read all these books that were at the library about fossils, so I determined that any fossil, a rock was a fossil that had five or more lines on it. That must be a fossil. So I went to my neighbor's rock garden and collected these...
Smith: So your sidewalk was pretty busy.
Rogers: Yeah. I had a collection in my room of all my rocks and fossils. But when I got a little older, I really wanted to be a paleontologist. And I had a chance to go on a dinosaur dig as a Girl Scout when I was about 14. I was still in Girl Scouts, but I was too young for this special camp to go on a dino dig at that time, and so my parents said, "If you stay in Girl Scouts until this comes around again, we will help you get there and try it out."
So I waited and waited, and I was a Girl Scout still at 16 when the other opportunity came around. And this time, it was actually to go to Egg Mountain, where the dinosaur eggs and babies I had read about in "The Weekly Reader" had been discovered.
And so I flew there, and I had my week long dinosaur dig, and I came back, and my parents were positive that I was going to be over it and I was going to be ready to like buckle down and be a professional French horn player or something. And I was the opposite; I was more excited about it than ever.
And so I spent my Senior year trying to figure out how to get there, and it was really expensive, and so I enrolled at a school in Missouri, where I was from, and I, behind my parents' back, also enrolled in Montana.
And I flew to Montana that summer for a summer job at Egg Mountain, and my hope was that I would run into Jack Horner, the model of the character for "Jurassic Park", and somehow, he would give me a job. He would think so greatly of me that he'd just give me a job.
Smith: Makes sense to me.
Rogers: It made sense to me too. So I got to Montana, I registered to vote, I got a driver's license, a post office box, I opened a bank account.
Smith: All of which your parents had no idea you were doing at the time, right?
Rogers: They had no idea. And so I worked on this dinosaur camp. And I ended up meeting Jack Horner, and within a couple hours, he said, "Well, why aren't you coming to school in Montana?" and I said, "Because I can't afford it," and he said, "Well, I'll give you a job if you come here." And so I said, "Great. You're on." So I flew home, and then a couple weeks later, I moved to Montana. And I finished my undergraduate degree there, and while I was there, he was an amazing advisor who essentially gave me free reign to do a research project of my own design and advised me along the way. So that's a rare opportunity.
I was the only undergraduate student in his lab. He had 19 graduate students at the time, but I was the only undergrad. So I always had funding, I always had a job. The grad students were in a little bit different boat, their positions were a little more precarious, but I always had what I needed to get my work done.
Smith: Well, if you knew how to, you know, get your residency and your own mailbox, I figure you could pretty much figure it all out. So what are you working on now, and what are you especially working on with your students at Macalester College now that you're in the Jack Horner position?
Rogers: In my own research right now, I'm working on naming a new dinosaur from Madagascar. So we have a skull that's different than the ones we've named before. So we're going to be naming a new dinosaur pretty soon. And with my students, I actually have a project that's funded by the NSF. So it's a project that's really focusing on how bones reflect environment stress in animals right now. So we see a lot of weird signals.
One of the ways we study dinosaur growth is to cut their bones into small pieces and look at them under a microscope and look for certain kinds of signals. Lines, rings, blood vessel spaces, and cell spaces, all those things are preserved, and they all tell us how dinosaurs grow. And they give us some idea that dinosaurs grow in a way that's a little different from other reptiles and a little different from other warm blooded, fast growing animals like mammals and birds.
So I started thinking about the idea that maybe they're growing differently because of the environmental stress that they're living through and sometimes dying because of. So most dinosaur bone beds are mediated by drought. So most of them are caused by a massive drought that kills off lots of animals and then they get buried and preserved for us to find. So I'm looking at dinosaur bones from Montana, Madagascar, Zimbabwe, and Argentina to look at their signals of their environment in their bones.
And then I'm also looking with my students at modern animals. So we're driving to a zoo in Wichita in May to pick up a bunch of dead animals, including a panther. So we're going to dissect out all their bones and thin section them to try to get a test on how different the bones are in a single skeleton. Surprisingly enough, no one's ever looked at that stuff before. And then how those bones reflect environmental stress. Then we can compare them back to the dinosaurs.
Smith: We have a few minutes for questions from the audience.
Doug: My name is Doug. I'm from Atwater, Minnesota. What I'm wondering is, a lot of times it looks like the dinosaurs are in a tropical environment. Does that account, possibly, for their size, and follow up, is that what changed, maybe, that made them go extinct?
Rogers: Great question. Thank you. Dinosaurs are usually depicted in these kinds of tropical settings, because a lot of times, that's where their bones are found, because that's where their bones are being deposited, right? Dinosaurs lived everywhere. They certainly lived in mountains. They certainly lived in forests and swamps and in deserts. But their bones are less likely to be preserved in those environments because of the kinds of things that preserve bones. You need water. You need sediment to preserve bones. You also need something that we call subsidence, where the surface of the Earth is dipping down a little bit.
And in a lot of those other places, the chemical environment or the depositional or sedimentary setting of the environment is not conducive to preservation. So, though we know dinosaurs lived everywhere, the chances are slimmer of finding them everywhere. So people usually try to reconstruct them in the kinds of environments in which they are found. The warm and tropical weather that was more common during dinosaur times certainly helped fuel their fast growth rates and their large body sizes, for sure.
And the second part of your question, why they went extinct? In terms of dinosaur extinction, if we think about the fact that dinosaurs are still with us as birds, we could argue that they're not extinct at all.
But because most of us think of the large bodied dinosaurs that do go extinct, there's really good evidence that suggest that they all went extinct in a few minutes after a major impact of an asteroid that hit the Yucatan Peninsula that's been dated to 65 million years ago. And there's a corresponding crater on the moon that dates from the same asteroid at the same time.
So we know it was a really massive event. There may have been several events of similar magnitude at the same time. So it was like the perfect storm. There was a lot of volcanism. There were a lot of asteroid impacts at this time. So we don't think dinosaurs failed to adapt to their environments, we think that their environment literally changed in a second, and they couldn't have possibly adapted fast enough.
Smith: And the idea that birds are the dinosaurs among us will have me refilling my bird feeder with a certain sense of humility that I didn't have before this.
Sean: Hi, my name is Sean Gould. I'm from Minneapolis, originally from Montana, Montana State grad. My question is in recent news, there are scientists trying to say bring back wooly mammoths. And if the technology and circumstances present themselves, do you think it's something important that we would try to bring back dinosaurs?
Rogers: So this field of evolutionary developmental biology is all about watching the genetic programs that turn major events on and off, like developing a tail or developing a limb or developing a fin. Jack Horner, interestingly enough, has a dream of building a Chickenosaurus. That's what he calls it. And his life's goal right now, and this late time in career, is to work with a genetic engineer to genetically engineer a chicken into a dinosaur. So he's hired a post doc whose job it is to go in and fiddle around with the genes and see if he can make a chicken with teeth and a chicken with a long tail and a chicken with scaly skin so he can bring it on a leash onto a talk show...
... And really illustrate for everyone in the audience that evolution really happens and that birds are really dinosaurs. So I think it's possible, but I don't think we would ever be able to recreate a dinosaur from frozen DNA, in the sense of wooly mammoth DNA. Dinosaurs really aren't preserved well enough in that regard to get that kind of data. Their bones are too old and too degraded. At least, we think they are. There's always the possibility that you'll find something really exceptional. But you could do it with a modern animal that you retooled, rewound evolution in the egg.
Smith: And like Jack Horner, then you would have it go off and live in Chickassic Park.
Rogers: Yeah. [laughs]
Ferris: My name is Ferris, from Coon Rapids, Minnesota. My question is if you only have the bones, how can you tell a new species from normal, individual differences.
Rogers: That is such a great question. You sometimes can't know for sure, right? So we try not to name a new species of dinosaur unless we see differences that are consistent across individuals. So most of the time, when people are naming a new animal, they're not naming it just for one bone or one skeleton. Usually there are a few parts of pieces of other skeletons that you're sticking together or amalgamating to really understand the diversity of the animals.
But in the old days, when people were just beginning to discover dinosaurs around the world, they often named dinosaurs on the basis of only one bone. And that means that there is a proliferation of dinosaur names that are not valid. They're not good names because they're based on really, really crappy fossils. So we have to revise all of them.
Smith: That's a scientific term, right?
Rogers: [laughs] Yes.
Rogers: Crapiolis. [laughs]
Katie: I'm Katie from the University of Saint Thomas, and I was recently reading a paper about sauropods, and I came across... It was talking about their neck structures, and I know you had briefly touched on that. And I read that in a couple of supplementary articles, and they were discussing whether or not sauropods are ectothermic or endothermic warm blooded versus cold blooded I was wondering what's the newer consensus about that? What's your opinion the fact? What do you think?
Rogers: So ectothermy versus endothermy is essential difference, as she said, between warm blooded and cold blooded animals, and because dinosaurs have scaly skin, we've always thought of them as cold blooded animals. And occasionally, people imagine that dinosaurs like sauropods are so big that they were able to retain their body heat and it would be harder for them to dissipate that body heat. So they would essentially be what we would call mass homeotherms. They were warm blooded just because they were so big.
Across all dinosaur diversity, the thing that's important to remember about them when we address these questions is that all dinosaurs, regardless of their body size, grow like mammals and birds. So all of them fuel a mammal and bird like growth rate. In the modern world, that is unprecedented unless you are a warm blooded animal. And when you're a juvenile, you're very small. And juveniles also have the same kinds of structures, indicating warm bloodedness that big animals have. So we think that, probably, most, if not all, dinosaurs were warm blooded. That's at least my opinion about dinosaurs and the opinion of some of my close colleagues. We don't see any good evidence for cold bloodedness in them, except for their scaly skin.
Smith: I'd call that a hot topic, but then you'd probably boo me for it. [Rogers laughs]
Mike: I'm Mike from Stillwater. I was just curious, when Stephen said that dinosaurs are the model for extinction, and we're sort of written often as that... Was that even with the fact that there were so many different varieties, so many different dinosaurs that had so many different adaptations that all of that was just overlooked back in the '80s, as you were saying?
Rogers: Yeah. I think that because dinosaurs aren't with us any more, people imagine them as these dead ends, these evolutionary dead ends. Too big. They painted themselves into an evolutionary corner that they couldn't get out of. But the reality is, just as you say, they're really diverse. They are, in fact, wildly diverse. And if you don't think about that diversity, and you only think about them in one way or another, you could imagine you could easily overlook their success.
But when you think about the fact that dinosaurs evolved 230 million years ago, survived as large animals on the surface of the Earth until an impact wiped them out in a matter of minutes, right? That's not their fault. That's not painting themselves into an evolution corner. That's being in the wrong place at the wrong time.
And when you think about the fact that we have only been here for, what, 200,000 years? Seven million if you go back as far as the first organisms that may have been like us, right? That's such a little, tiny drop in the bucket compared to dinosaurs that I find it really hard to imagine them as anything but wild evolutionary success stories.
Smith: We're but a mote in the eye of the meekest dinosaur that ever lived. [audience laughs]
Rogers: [laughs] It's so true.
John: My name is John, and I have one question. What about the so called mole commembe [?] of Africa? People say it was like an ancient apatosaurus, formerly brontosaurus. Do you put any stock in that?
Rogers: Yeah, so a lot of legends of mythical creatures, we think, are based on dinosaur bones, based on the discovery of dinosaur bones. So if you've ever heard of the thunderbird from the Navajo nation and from the Pueblo nation, a lot of those stories are based on discovering, we think, huge dinosaur bones that were very human like in their shape.
The story of the gryphon is another one you may have heard of. People think that it started in Mongolia, and because they are finding these crazy dinosaurs that are preserved sitting up, that have frilled skulls, the beaks like a lion, and claws on their fingers, they look like a flying lion with a beak. They look like a gryphon. So a lot of legends, we think, are based on early peoples' interpretations of these bones. So isn't this one from the Congo, this dinosaur?
John: It's supposed to be like the ancient brontosaurus.
Rogers: So there is this legend of this long necked dinosaur still alive in the Congo. It could be a Loch Ness Monster style story. But it may be based on some reality. Someone at some point may have found a sauropod bone or another large dinosaur bone in that area and then created a story to explain it, right? So, I think it's probably not a real sauropod walking around. It seems like they'd be hard to hide. They're pretty big [laughs] .
Smith: Kristi Curry Rogers, thank you so much.
Rogers: Thanks. [audience applause]