The Titanosaur, Patagotitan mayorum, is the largest-known dinosaur to ever walk the Earth—weighing more than 10 African elephants. How did it get so big? How did it dominate the prehistoric landscape for millions of years? And what can this extinct animal teach us about our own future on this planet? Join paleontologist Diego Pol as he explores these questions and recounts his journey leading the team that discovered the Museum’s Titanosaur.
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DIEGO POL (PALEONTOLOGIST, MUSEUM OF PALEONTOLOGY EGIDIO FERGUGLIO; RESEARCH ASSOCIATE, AMNH): Good evening everybody. I'm very, very happy to be here. I came to this museum when I was 20-something. I still remember the first day when I got here. I was very excited about starting my Ph.D. and about becoming a paleontologist, but I really didn't have much of an idea of the wonderful journey I was going to start. A journey that took me to trace the history of some of the greatest dinosaurs that existed on our planet. Sauropod dinosaurs—these long-neck quadrupedal animals with a long neck and long tail—were actually dominant in our planet for over a hundred million years. These animals were amazing, they were one of the three major families of dinosaurs that we know of, together with ornithischians and theropods, the ones that later gave rise to birds.
And these animals are very, very important not only because they were the dominant herbivores for millions of years, but also because they have a tremendous body size. So they are up to ten times larger than any other sauropod, than any other dinosaur. And they are over ten times larger than all the mammals that we know, and also the largest mammals that we know today–elephants. Now, when we look at the deep history of mammals across the last 200 million years, we see that at the beginning they were very small. And only in the last 66 million years after dinosaurs went extinct, the maximum body size of mammals went up. And they barely cross that red line that marked the limit–20,000 pounds–that's the biggest that a mammal got in the history of life. Now, sauropods, on the other hand, didn't have much trouble going above that. Soon after they appear they went above that limit and then way, way beyond, way up there until 66 million years ago, they disappeared completely from the face of our planet.
Sauropods were also very successful in conquering all the continents. We have found sauropods in all six continents on our planet. And I've been looking around sauropods and their relatives in different places in our planet, but especially during the last few years I've been focusing in this region–the southern tip of South America, we call this Patagonia. About ten years ago I moved down there to the city of Trelew. And this is a museum where I work, and I went there because this is the place were the most wonderful sauropod dinosaurs had been discovered.
So we have been working in the desert there, trying to find new clues to understand the history and evolution of this wonderful group. A few years ago we were at the museum and we received a phone call from a farmer that lived nearby, saying that he had found some dinosaur bones in the ranch. When dinosaur bones appear in the desert, they usually start coming out very slowly because the erosion is eroding away, blowing away the sand, and we only see the tip of the bone coming out of the ground. So a team of the museum went to this to this place, and the rancher took us to this place and they show us a bone, and what we saw there was a tip of the leg bone of the Titanosaur that was just coming out of the ground.
A few days later, after excavating this bone, we found that this was a gigantic bone. A bone that is much taller than me. So soon we realized this was a gigantic animal, probably the largest dinosaur ever in the history of life. The largest land animal that walked on our planet. This bone was very important because it was the first bone that appeared and it showed us that this was a super-sized animal, but the most important part was that after this bone, we opened a quarry and many other bones showed up. So after working for a year and a half in this in this place, we collected over 150 bones.
This is a 3D map of excavation in the quarry, and it shows how many bones were scattered around. And these remains belong to six different individuals that died in this particular place. So for the first time, we had a good idea of how these gigantic dinosaurs looked like. Because we previously knew other species that were big, but we only knew a few bones from those species. This is my colleague, Jose Luis, that is studying one of the remains of Argentinosaurus, a really big dinosaur, but we only knew five bones from that species. So we only had like a very, very, very small glimpse of the anatomy of the giant dinosaurs.
So this quarry of Patagotitan, it's very important because it is the first time we have a very complete idea of how big this animal was, and how the skeleton was built, how was the body plan, how's the architecture of these gigantic animals? We can learn a lot from having different parts of the skeleton. For instance, it's very important to have a fairly complete skeleton to estimate something very basic of these species–how heavy this animal was, how was the body mass? And there are two bones that are very, very important for that. The humerus, these bones in the front limb, and the femur, these bones in the hind limb.
All the body weight has to be supported by these two bones. So the weakest point in these bones are the mid shaft–so imagine that all the body weight of the animal has to go through those two pieces. So scientists have shown for a long time that there is a very good correlation between the measurement of the mid-shaft of the femur and the humerus and the body mass. In this graph, we see in the horizontal axis the measurement of the limb bones, and the y-axis, the vertical axis, the body mass, how heavy these animals were. And every single dot there is a living species for which we can measure the limb bones and at the same time, we can measure how heavy the animals were. And you can see there's a fairly nice correlation. And the white lines show the ninety-five percent confidence intervals.
So we can measure the bones of Patagotitan and plot it there, and then go up and see where it crosses the blue line, and get an estimate how heavy this animal was with a confidence interval. The conclusion is that these animals weighed 69 tons, about one hundred and forty thousand pounds, plus/minus ten thousand pounds, this is the error we have in the estimate. This is the equivalent of 10 African Elephants. It's a really, really big animal–the largest land animal we know. As large as a Boeing-737. And even though it's about 69 tons–same weight that this plane can have before taking off–it can take off because it has these powerful turbines that make the motion that makes this plane take off. But our Patagotitan, these animals didn't have any engines, they had these muscles.
And this is one area of research that prompted our discovery, we’re trying to understand now from the biomechanical point of view how this animal was able to move around, how the muscles were built so that it this animal can function as a biological organism. So all sorts of very interesting questions are prompted by the discovery of this wonderful creature. But after discovering this animal, I tell you we were expecting something that didn't happen. We were expecting this animal to be very different from other sauropods. We were expecting this super-sized animal to be very different from their smaller relatives, have unique adaptations in the skeleton that allowed them to grow that big. But we were wrong.
This animal is just a scaled up version of the smaller relatives. And this is wonderful, although it was against all the expectations we had. This is wonderful because it shows how this body plan, this sauropod body plan, was so successful and stable that [it could] spread along a very, very broad range of body sizes. Animals that were about the size of one elephant, to animals that were about the size of ten elephants. And not only this body plan was very successful in terms of the breadth of body sizes, but also in terms of how long these animals lived. Sauropods dominated the herbivore niches on our planet for over a hundred million years, and they didn't change that much during all this period. So we have this wonderful period of stability and success. These animals came up with these body skeletons that were so fantastic, that actually made them the dominant species, and the dominant group in our planet.
So we had to go on and dissect this whole plan, you know, how can we find out about these different parts of the skeleton and what was the key of the success of these animals. A big part of that is having a long neck, long tail, and very, very strong columnar limbs. That's a basic feature of this animal, and you can see that in any sauropod. This is the Titanosaur on the fourth floor, you can see that it has very strong, very powerful limbs. And you have the long neck and the long tail, and in between the backbone that connects the entire skeleton. And this structure with strong pillars and long, stable backbone, it's not that different from a bridge. You have one pillar, the other pillar, and the long and stiff part that joins between them. Now, the part in between the two limbs, the backbone here have vertebrae that are very, very interesting. They are interlocking with each other at a very, very tightly, and they're tall, they're very complex, and they're hollow. So we're going to get into that right now.
You probably all know this, right? A T-bone steak, right? So the T-bone steak is half of the vertebrae and the muscles on the side. When we mirror them we have those complete vertebrae. And in the vertebrae, we have the top spine–the bone that goes up–and then the bone that goes onto the side that we call the transverse processes. And in between those we have the meat. These are the cross-section of the muscles that go along the back, and these muscles are very important for locomotion. They're very important for the stability and for the support of the entire backbone. When we look at the vertebrae of Patagotitan we see that it has a fundamentally different structure. It has a much higher neural spine, and that means that the muscle that should have gone all the way in between the spine and the transverse process was much, much bigger in proportion. So when we take into account the difference in body size, we can estimate that one T-bone steak of the Titanosaur was about 1,000 T-bone steaks of a cow. Quite impressive.
Now, the vertebrae of sauropods are not only important and impressive because of the size and how high they were, but it's also because of the shape and all the internal structure. So normally, the vertebrae of other animals are very simple, it has a body–a solid body in the bottom–the spine going back up, and then has a processes going to the front, and some processes going to the back. Sauropods have much taller vertebrae, but also have a complex set of the bony lamina that encloses this deep socket that communicates with internal chambers within the vertebrae. So by doing CT scans of some of the vertebrae of sauropods, several studies have shown that up to 50% of the volume of the vertebrae was occupied by air. So the vertebrae, the backbone of sauropods, was not only super tall and housed these super big muscles, but also was very resistant because of this cross lamina and was very light because of the internal hollow structure it had.
Another important aspect of sauropods is in the skull. They were bulk feeders. They have a relatively small head, but with a big mouth, and these animals were probably eating all day long. They have big teeth that were very well adapted for cropping the leaves and the branches. They didn't do my chewing, they had teeth just adapted to cut and swallow plant materials, branches and leaves and whatever they can find. Another aspect of sauropods that is very important is they were growing really fast. And we have learned that by cutting the bones. And when you cut the bones you can see how the bony tissue got deposited during the growth of the animal, and by studying how fast these deposits of bone tissue appear in the cross-section of the bones, we can estimate these animals were putting on several thousand pounds per year during their active growth. So one of the keys for gigantism was that they were able to grow really, really fast. Finally, these animals lived in herds. And we know from different discoveries all around the planet that they were making these group nesting grounds, the colonial nesting grounds, and different nests were made very, very close to each other to protect their young.
So this may be some of the keys that explain the success of these animals during a period of over a hundred million years. But although this may explain that stability and success in the dinosaur times, what happened before that? This actually opened new questions. We know the first dinosaur that appeared about 230 million years ago were these tiny small bipedal animals that were not bigger than a dog. And at some point, something changed and the herbivores became so big and so dominant that they dominated our planet for a hundred million years. So this focused, then, our research to that period in the about 200 million years, something must have happened in there that we need to understand. And then we focus on to that time slice. This particular time slice in between the Triassic period and the Jurassic period, something must have been going on there.
So this is our planet two hundred million years ago, all the continents were together. And in the southern hemisphere where we have a thriving fauna of dinosaurs, early dinosaurs, that we know from the fossil record in what is now South America, and South Africa, and Antarctica. All the southern continents were clustered together forming the supercontinent Gondwana. In the last fifteen years, we have been very lucky and discovered many dinosaur species in South America only. All these dinosaur species have been discovered in the last fifteen years and we're learning a lot from them. One of the basic outcomes of these discoveries is that in that period of around 200 million years, we have a diverse fauna of sauropod relatives and also early sauropods that coexisted together. And some of the early sauropods were already really big, but they coexisted for quite a long time. And we find out, then, that some of the features that we thought were unique of the big gigantic sauropods where in fact really present back then in this early period in sauropod evolution about 200 million years ago.
One of them is the communal nesting habits. We have found nests like this grouped up in one locality and the eggs within those nests have embryonic remains. Through CT scans we can identify who was laying the eggs because we know the embryos inside. And this is a sauropod relative. So even before the evolution of sauropods, this communal behavior was already going on. The vertebrae were really big, tall, and hollow. We thought it was unique of the big gigantic sauropods, but we were wrong. This was present in this early phase of dinosaur evolution. You know, big tall vertebrae with deep sockets, communicating to internal chambers, they were already present for a long time, long before the domination of sauropods.
We also know that there were big sauropods that were growing really fast. Last year we found new specimens of this species on the top, Lessemsaurus, very similar to a new species from South Africa that colleagues across the Atlantic Ocean found. These animals were twice the size of an elephant and showed that early in this period about 200 million years ago, they were already passing that mark of the ten-ton limit, and they achieved this process because they were growing really fast. We made sections of the limb bones and we can see in the bone tissue that these animals were growing really, really fast, as fast as sauropods.
So we're facing now a new situation in which, way before the long period of stability of giantism in dinosaurs, we have an early phase in which giant dinosaurs were already here and they were coexisting with many other relatives that were much smaller in body size. So again we discover that we were wrong in thinking that these features were key for explaining the success of big, gigantic sauropod dinosaurs. Something must have happened in between those two periods that explain this change between the coexistence of gigantic dinosaurs with other species much smaller in body size, to a second phase that was completely dominated and exclusively dominated by giant sauropods. And we had dates to narrow down that change between 190-180 million years. So we're now facing that gap, we have to fill that gap. What happened in those ten million years that changed our planet for good, changed the communities of plant-eaters in a very, very significant way.
So we went looking for dinosaurs in this particular time frame. And you know what? We didn't find a single bone. Because all the rocks that we have from that particular period in South America are rocks like this. These are volcanic rocks, giant lava flows were occupying most of South America at that time. This is in northern Patagonia. All these rocks that you can see up to the horizon are volcanic rocks that erupted 185 million years ago. We went 500 miles south from this point and we found the same rocks, 185 million-year-old volcanic rocks. This is telling us about the massive volcanic eruption that was happening on our planet at this time. And not only in South America. When we look at the rocks in different parts of the southern hemisphere we find the same rocks in South Africa and in Antarctica. This is telling us a story about a massive volcanic eruption. We estimate this volcanic eruption occupied a million square miles, lava flows extending over a million square miles. The largest lava flow we have seen in recent times is a hundred square miles.
Now, you can imagine that this lava flow, this volcanic eruption, released through to the atmosphere carbon dioxide and methane in large quantities and in a very, very short amount of time. We're estimating this between the hundreds and a few thousand years. And the rock record and the fossil record is showing that our planet was severely affected by this high input of CO2 and methane. These are the curves that show how the carbon and oxygen isotopes change through time in the rock record, and you can see how right at this time there's a big change in the carbon and the oxygen isotopes. Which is telling about phases of global warming, climate change, and drastic environmental change in our planet. And this has been recorded not only the southern hemisphere but all over the planet in Europe, in the U.S., in Asia, the records of this drastic climatic and environmental change caused by these massive volcanic eruptions and the input of CO2 and methane into our atmosphere. And this is linked to this extinction event where many of the dinosaur species that were living at that time completely disappeared. And then after that is when we see the dominance of the big gigantic dinosaurs.
Now one of the interesting things about the record in Patagonia is that we have the volcanic rocks, but we have fossils from before and after the volcanic event, too. So we can understand how life changed not only in dinosaurs but other organisms. And we can see that not only dinosaurs were affected, but entire ecosystems were affected. The plants were affected: before we have a high diversity assemblage of ferns, and seed ferns, and conifers, and cycads, indicative of humid and very warm climate. And after that, we have a very low diversity of only conifers and some cycads, indicative of hot and dry environments.
So when we found that the extinction of all the small dinosaurs and the dominance of the big ones were linked to environmental changes, it suddenly became very obvious that it’s not enough how big you are, it’s not enough how successful you are as a species. It’s not enough how many wonderful adaptations you have in your skeleton, or your brain for that matter, how many wonderful behaviors you have. At the end of the day, it is the environment that will determine if your species will be successful or not through time. And especially in this breaking point in the history of life, we see that a planet determines new rules and new conditions that determine what species will make it through and what species will not.
The journey that we took from the giant dinosaurs that lived on our planet about 100 million years ago, down to the origins of the giants 200 million years ago, then to the discovery of this critical breaking point in the history of dinosaurs that was caused by extrinsic forces like volcanism and climatic change, can actually give us a very important take-home lessons that I think we should get. There is a history of our planet, it's written in all these rocks, and we need to learn the lessons from the past to understand the future and present of our planet.
This is what paleontology is about: learning and reading these histories from the rocks. And we can do that with the help of many people. People like you that support science and care about science to come here in a Wednesday afternoon, and people like all the students and volunteers that help us during the expeditions, getting all these fossils from the deserts in Patagonia to understand the history of life in this particular part of the planet. And helping us to put together this puzzle that is the history of life on our planet. So thank you very much. I thank you for everything.
This SciCafe took place at the Museum on May 1, 2019.