Episode 5: The strange tail of Spinosaurus

In the Sahara, National Geographic explorer Nizar Ibrahim discovered a 15-foot fossil tail that will forever change the way we think about dinosaurs.

A craftsman molds an updated tail for a life-size re-creation of a Spinosaurus subadult in Fossalta di Piave, Italy.
Photograph by Paolo Verzone

Spinosaurus has long been a superstar among dinosaur fans, with its massive alligator- like body and a huge “sail” of skin running the length of its spine. Though the fossil was unearthed a century ago, scientists hadn’t been able to say exactly what it looked like because only a few bones had ever been found. But new fossil discoveries by National Geographic explorer Nizar Ibrahim will forever change the way we think about Spinosaurus—and all other dinosaurs.


NIZAR IBRAHIM (PALEONTOLOGIST): So, things to watch out for when we’re actually out in the field—and this is really serious. It kind of feels really surreal, and you think like, you know, like this is in a movie or something. But the problem is in a movie it’s stuntmen and fake snakes, and, you know, a wind machine. But we’ll have real snakes and scorpions, and if you fall, you actually break your leg. There’s no stuntmen. So you really have to watch your step. I hope you all have good shoes.

PETER GWIN (HOST): This is a recording from early 2019. Paleontologist Nizar Ibrahim is about to take a few students and one of our writers out into the field to investigate a new discovery, and maybe even find a few fossils.

IBRAHIM: If you find a little piece of bone, and you're not sure if it’s bone, one thing that you can do, and you will do that—is stick your tongue on it. So if it sticks...

MICHAEL GRESHKO (WRITER): If it sticks, it’s bone.


GWIN: The bones they hoped to be licking once supported the hulking body of a dinosaur called Spinosaurus. All right, I confess I was that kid who was way into dinosaurs. And I remember this guy from a coloring book as the one with the big sail on its back. It kind of looked like a dragon. As it turns out, there is only one known skeleton of Spinosaurus in existence. Nizar discovered the first half of that skeleton in 2013, but the rest of the dinosaur was buried under tons of rock. That is, until now.

IBRAHIM: We hit the jackpot, and we found bone, after bone, after bone. You always heard someone say “bone” somewhere.

GWIN: Wow, this is bone after bone of Spinosaurus?

IBRAHIM: Yes. It was wild. But the thing that really, really made my heart pound was when we excavated one of the tail bones from very close to the tip of the tail. And I thought, well, it's going to end any time now, but it got longer and longer. And we were removing more and more rock. And it just kept going and going into the rock. It was

ridiculous. I had never seen anything like this before. And that's when we knew we were onto something really exciting. That's when we realized that this was going to rewrite the dinosaur textbooks.

GWIN: OK, if you have a dinosaur book at home, break out the Wite- Out and turn to the page on Spinosaurus because Nizar has a few corrections to make—straight from the Sahara desert.

I’m Peter Gwin, an editor at large at National Geographic magazine. And this is Overheard at National Geographic: A show where we eavesdrop on the wild conversations we have at Nat Geo, and follow them to the edges of our big, weird, beautiful world.

This week: The strange tail of Spinosaurus. We’ll follow Nizar out to his dig site in Morocco to solve a long-standing dinosaur mystery.

More after the break.

GRESHKO: So you start out in the town of Erfoud, Morocco...

GWIN: This is my colleague, National Geographic science writer Michael Greshko. He was on the other end of Nizar’s safety lecture and was just about to start looking for dinosaur bones.

GRESHKO: And you'd just start driving out to where there is no more road. And then you get out and then you hike up this sort of steep escarpment to the dig site itself, which is this little spit of exposed, dug-up red sandstone on like a vast expanse of sandy colored rock. And then you get to work. It's dumping rocks over the side and tumbling down the hill in, like, buckets made out of recycled tires. And it's fueling the jackhammer. And it's the smell of the fumes and the sound of people brushing and chipping away with rock hammers. And then you do that for 10, 12 hours, and you go back and you do it again.

GWIN: A jackhammer might seem like overkill for fossil hunting, but the bones they were looking for had been buried for millions of years under some 15 tons of rock. Nizar and his team knew exactly what they were looking for, so it was safe to use power tools until they

knew they were close.

GRESHKO: We're digging through. And then all of a sudden, you know, Gabriele sees something. And he's—he sort of stops, and he's like, stop, stop, stop.

[Recording: “I think... maybe... yes. Bone? Bone, bone, bone, bone. We found it!”]

GRESHKO: I think it was the first true bone that we had found.

[Recording: “Are you happy? Me and you?”]

GWIN: Was—is there sort of a palpable sense of excitement that—I mean after all this hard work...

GRESHKO: One hundred percent. Yeah, it's—I mean, you have to mentally prepare yourself for like not finding anything at all. But the second that there is an announcement of bone, it's just—it's electric. Once you find one thing, then the mind races, and it's like, well, how much more is there?

GWIN: A lot more, as it would turn out. Michael had come to see Nizar coax some of the last few bones of Spinosaurus out of the rock in an attempt to settle a mystery that had started more than a hundred years ago.

GRESHKO: Spinosaurus was found in the 1910s by a guy named Ernst Freiherr Stromer von Reichenbach. We're gonna call him Ernst Stromer for the rest of this.

GWIN: There you go. OK. Right.

GRESHKO: So this Bavarian aristocrat and paleontologist named Ernst Stromer described this material that came out of Egypt in the 1910s. And in the original description of this material, Stromer names it Spinosaurus because of these spines—these like six-foot-long

extensions of its vertebrae that seem to have formed like a big sail of sorts on its back.

GWIN: What do you mean? Like a sailfish kind of thing? Like that kind of sail?

GRESHKO: Yeah. Sort of. I mean, whatever it was, it was big.

GWIN: Stromer didn’t have much to go off of, just a handful of bones: some ribs, the lower jaw, and seven of those giant spines. But before he could learn more, the fossils were reduced to rubble.

GRESHKO: So these fossils and others that were recovered from Egypt, he brought them to a museum in Munich, put them on display —they were quite the sensation. Unfortunately, they were destroyed in a bombing raid in World War II, in 1944. So lots of question marks around what this dinosaur was and how it lived and evolved have eluded researchers ever since.

GWIN: From a scientific point of view, the fact that these things had survived for millions of years and they get wiped out in a bombing raid is just—it just feels like the ultimate, you know, cruel twist of fate. You know, just at the moment, we're about to discover this strange dragon-like creature and then... smithereens.

GRESHKO: Yeah. It's quite the twist, and one that takes decades to try to get past.

GWIN: Aside from a few small fragments, no new Spinosaurus were found for 50 years. Basically everything the scientists knew about the dinosaur came just from Stromer’s sketches and notes. It was one of the most famous dinosaurs in the world, yet there were no skeletons to study. And along with Spinosaurus, the bombing raid wiped out one of the largest collections of African dinosaur fossils in the world, which dealt a massive blow to paleontology. Nizar Ibrahim, whose mom is German and dad is Moroccan, noticed this at an early age.

IBRAHIM: I was born in Berlin, you know, so I spent a lot of time going to the museum there and reading books on dinosaurs, as all young dinosaur fanatics do. But then even as a child, you notice that some parts of the world are really underrepresented. In particular, Africa.

GWIN: There’re a lot of reasons that not many fossils have been found in Africa. History, politics, and even discrimination.

IBRAHIM: I always thought, you know, we have dozens of skeletons of T. rex, but wouldn't it be great to find a new Spinosaurus and shine light on this, you know, overlooked and forgotten continent in paleontology—Africa?

GWIN: And so as a young Ph.D. student, Nizar decided to write his thesis on African dinosaurs. And in 2008, he was leading an expedition in the Sahara.

IBRAHIM: On one of our expeditions, we stopped in a small oasis town in the middle of nowhere. And while we were there, a local man showed us that cardboard box filled with fossils.

GWIN: The man was a fossil hunter selling to tourists and collectors. It would be hard to say anything scientifically about the bones without knowing where they came from, but they did give little clues about what might be out there.

IBRAHIM: One bone caught my eye. And it was a blade-shaped piece of bone. And I had never seen anything quite like it before, and I thought, you know, I’m not sure what exactly this is, but this is maybe something important and it looks like all of these bones were found together.

GWIN: In pictures it looks like a leaf or a pointy oval. It’s about the length of a human pinky, with a red streak running right across the

middle. It was a cross-section of some kind of flat bone. Like a rib, but it didn’t look like any rib Nizar had ever seen. He bought the fossil and then donated it to the University of Casablanca, which—without knowing more about it—was really all he could do.

IBRAHIM: I always thought, you know, one day I'm going to figure out what this is.

GWIN: The back rooms of museums all over the world are filled with these lonely little puzzle pieces. Like a corner of a receipt that proves something lived here a long time ago, and we’ll never know what unless a scientist gets very, very lucky.

Nizar’s first piece of luck came one year later.

IBRAHIM: And so I was visiting museum collections all around the world. And my Italian colleagues showed me all their African fossil collection, but they also wanted to show me something else. They said that they have a partial skeleton of a dinosaur sitting in the basement of their museum.

GWIN: A geologist had recently donated the partial skeleton, and the museum didn’t have much information about it, other than they thought it came from North Africa.

IBRAHIM: And so we went to look at the skeleton, and the bones were laid out on big tables. And I looked at the bones and my jaw just dropped. There were big, tall spines. And it wasn't just spines, there were also backbones and leg bones, jaw pieces. And so we were pretty confident that we're looking at a partial skeleton of Spinosaurus. We were excited. But then we also knew we had a really big problem because my Italian colleagues did not know where exactly these bones had been found.

GWIN: Mm-hmm.

IBRAHIM: And that's a massive problem in paleontology, because if you don't have any contextual geological information, the specimen

is, you know, I don't wanna say worthless, but, you know, it's really very difficult to say anything about, say, the environment the animal lived in. But perhaps most importantly, you also don't know if all of these bones really belong to one individual, right? And I just felt my heart sinking.

GWIN: That was it. It seemed like another dead end in the Spinosaurus saga. As long as he had no idea where it came from, this partial skeleton would just be a curiosity.

IBRAHIM: But then I picked up one chunk of spine. And it immediately clicked.

It was a few inches long and kind of a brownish and it had a noticeable red streak running through it.

IBRAHIM: This chunk of spine in its color and texture looked exactly like the strange chunk of spine I had found in the cardboard box in Morocco. And I thought, you know what, these bones are so similar. Maybe they actually belong to the same skeleton, right?

GWIN: Oh wow.

IBRAHIM: I thought, so I guess I can find the dig site. All I need to do is find one man in the Sahara Desert, right? The man with the cardboard box.

GWIN: OK, I know what you’re thinking: the Sahara is a big place, and by the way, in Morocco fossil dealing is a huge industry.

GRESHKO: In this particular region of Morocco, for tens of thousands of people, like their livelihoods directly or indirectly rely on the fossil market.

GWIN: Tens of thousands.


GWIN: That's a lot. Just like it's hard to imagine that many people all finding fossils.

GRESHKO: I mean, there's a whole supply chain to it. So you have people who are digging, by hand, with pieces like sharpened pieces of rebar. And they are tunneling into the rock formations to try to find dinosaur teeth and bone and other kinds of animal remains as well.

GWIN: Nizar showed Michael one of these hand-dug fossil mines while they were out in Morocco.

[Recording: GRESHKO: So it’s a small triangular shaft. Goes back, I don’t know, 10-20 meters. It’s just big enough that I can squat.]

GRESHKO: It is not the safest work. You know, you can breathe in the dust, which can cause lung damage over time. These tunnels can collapse and sometimes do.

[Recording: GRESHKO: Yeah. This is how they make their living.]

GWIN: Officially, Moroccans need a special permit for archaeological digs, and without one it’s illegal to export fossils from the country. But Moroccan fossils can still be found in collections and museums all over the world.

GRESHKO: And the industry has matured to the point that there’s a whole network of wholesalers and exporters who are aggressively buying as much as they can from dealers—often, you know, pennies to the dollar for what they will eventually export for and sell.

GWIN: On the one hand, this huge cottage industry was how Nizar found out about the Spinosaurus fossil in the first place. But it also

made finding the man who could show him where it came from very tricky, and Nizar had a hard time convincing his Moroccan teammate it could even be done.

IBRAHIM: When I told him about my plans, he just looked at me like I was a lunatic and said, How are you going to find him, right? Do you have his address? And I said no. Do you have his name? Nope. Do you have a phone number? I said nope. And so he said, Well, how are we going to find him? And I kind of felt like I had to say something. And so I said, You know, I do remember one thing, and I'm 100 percent sure about this. The man we're looking for has a mustache.

GWIN: Let’s just say mustaches are popular in Morocco. And it had been about six years since Nizar had seen the guy. But it was Nizar’s only lead, and he felt like he had to try. National Geographic gave him a grant basically to find that mustached man who might be able to lead him to the dig site and connect this final piece of the puzzle. They went from town to town, but no one had heard of this man, or his dinosaur.

IBRAHIM: And just when I was ready to throw in the towel, when I was this close to giving up, things suddenly changed. On our very last day, we were sitting in a cafe in an oasis town, sipping mint tea, and basically burying all our hopes of ever finding this man. And just as we're doing that, a man walks past our table.And he did have a mustache. And he looked very familiar. All of a sudden I was like, was that the guy? Or am I just hallucinating. Was that the guy? So I got up and I caught up with him. And after just a few moments, it became clear that this was the man we had been looking for.

GWIN: Oh my gosh.

IBRAHIM: And he recognized me. And here's what he told me: He said, yeah, you know, I had found a few bones at this new dig site. And those are the bones I gave you in the cardboard box. And he then told me, I then returned to the dig site and I found many more bones. And I said, well, what did you do with these other bones? And

he said, Oh, I sold these to an Italian man.

GWIN: Suddenly, it seemed much more likely that this was the man who had found the partial Spinosaurus that now lay in the basement of the Italian museum. Nizar asked the man to show him where he’d found the fossil. But the mustached man was reluctant; he didn’t think there were more bones to find there. But Nizar wouldn’t take no for an answer. And so the mustached man guided them past an oasis to a place where the roads ended, and then they hiked to an isolated plateau in the desert. It wasn’t a place Nizar would normally have looked for fossils, but it was exactly what he had been looking for.

IBRAHIM: And at the dig site, I found little pieces of bone. And they had the same texture and color as the ones, you know, I had seen in Italy and the ones in the cardboard box, little fragments of spine. And so I knew, you know, we were at the right place.

GWIN: Nizar’s hunch was right. The bones found there—combined with the ones from the Italian museum—yielded the most complete Spinosaurus fossil ever found. And it gave Nizar new evidence to make a provocative statement about how this creature lived:

IBRAHIM: It is a water-loving dinosaur.

GWIN: Today, the spot where Spinosaurus was found is in the Sahara desert—not great for the swimming lifestyle. But 100 million years ago, the Sahara looked a lot different.

IBRAHIM: It was a huge river system. But on a scale that we could not even begin to imagine. This river system stretched all across North Africa. So from Morocco all the way to Egypt. That’s an area about the size of the United States. And it was home to giants. Giant fish, giant crocs, giant predatory dinosaurs. It was probably the most dangerous place in the history of planet Earth. A river of giants. A place where, as a human time traveler, you wouldn't last very long.

GWIN: And the biggest predator there was Spinosaurus.

IBRAHIM: Spinosaurus itself essentially was the river monster that ruled this bizarre ancient world.

GWIN: Nizar’s analysis was groundbreaking. Until now, all the dinosaurs we knew of either walked or flew. Paleontologists had never identified a species specialized for swimming. It was like saying Nizar had discovered a great white shark that liked to hunt on land.

IBRAHIM: You know, when you grow up reading dinosaur books, there is a page on marine reptiles, like the dolphin-like ichthyosaurs and so on. And it says, well, these are marine reptiles. They're no aquatic dinosaurs, right? No swimming dinosaurs.

GWIN: Right.

IBRAHIM: So we all knew this was going to rewrite the textbooks— and the children's books—in a pretty fundamental way, and it would open a whole new window of ecological opportunities.

GWIN: So what is it about the bones that gives away that Spinosaurus was this aquatic animal?

IBRAHIM: Well, we knew about some circumstantial evidence, right? So Spinosaurus has conical teeth, which are great to grab and catch slippery prey, like fish. So this is something we see in crocs, for example. But then we also had some evidence from the bones themselves. If you look at the inside of, say, the thigh bone of Spinosaurus, you realize that it's very dense.

GWIN: Nizar explained that most land animals, even huge elephants, have hollow spaces inside their bones for marrow. But not Spinosaurus.

IBRAHIM: So the bones are dense and heavy. And this is something

we see in animals like manatees, for example, animals that spend a lot of time in the water. It turns out the dense bone is important in buoyancy control.

GWIN: But not all scientists were ready to accept the idea that


unlike any other dinosaur, lived like a manatee. And a few academic papers challenged Nizar’s claim that Spinosaurus was aquatic.

IBRAHIM: And much of the opposition was not really based on very convincing evidence. But there was one point I had to concede. And that was that we did not have a plausible mode of locomotion for this animal. You know, we kind of said, well, maybe it's kind of paddling with its hind feet. But essentially, we didn't have a motor that— that would move this thing through the water.

GWIN: Like a propeller.

IBRAHIM: Exactly. What was propelling this animal through the water?

GWIN: Finally in 2019, Nizar and his team had the last piece of evidence they needed to prove Spinosaurus was aquatic—his motor. The main reason Michael Greshko went to Morocco was to see that aquatic motor.

GRESHKO: We drive to the university. We take a left and, you know, above the door there's a little plaque that says, you know, oh, this is the paleontology lab. And I opened the door and across several tables that had been sort of jammed together in the middle of this room is the first complete tail of Spinosaurus. And it stretches like, I mean, it's like 15, 16, 17 feet long.

GWIN: Wow. Just the tail.

GRESHKO: Just the tail. Just the tail. And it just—it basically takes up the entire length of the room. And I just remember turning the corner

and just my mouth like dropped open. And I was like, what am I looking at? What am I looking at? Because it's—not only is it so big— this is a big dinosaur. Not only is it so complete—they probably have, I don't know, 60 to 70 percent of the whole tail at least. But also it's a weird tail. It's super weird.

GWIN: Spinosaurus belongs to a group of dinosaurs called the tetanurans. They’re the ones that look like T. rex or velociraptor. The word “tenanuran” means stiff tail. And these dinosaurs are known for having round, stiff tails. They’re good for balance as they run around on two legs. But Spinosaurus’s tail was basically the opposite of that. It’s flat, rectangular, and would have been very bendy.
No other dinosaur in this group has a tail like this, but Nizar thought he knew what it was for.

IBRAHIM: And sure enough, when you put everything together, we realized that this was a structure that looked like a giant fin, right? A tail fin. A tail paddle. We had found our propulsive structure.

GWIN: This long, flat tail seems built for pushing through the water— like a crocodile. In other words, a powerful aquatic motor.

IBRAHIM: When I started piecing the skeleton together and I realized that this, you know, was a dinosaur like no other. Of course, I couldn't help thinking, you know, wouldn't it be great if Stromer could see this?

GWIN: Since Nizar is both German and Moroccan, in some ways it feels like he was the perfect person to find this fossil—and answer a century’s worth of questions that have surrounded this iconic dinosaur.

IBRAHIM: So for me, it was not just a scientific adventure. It was a personal one in many ways, because also as a German, I had a different way to look at this, right? I could read all the original expedition diaries, I visited the site where the original museum was standing, right in Munich. so it was a journey back in time in my own country. And it was a personal journey that started when I was four or

five years old.

GWIN: Now as an adult, Nizar plans to return to Germany and unveil a life-size model of Spinosaurus. It looks pretty different from what Stromer and other paleontologists might have expected. And Nizar hopes the bones will remain where they were found in Morocco and eventually become part of a museum where they can inspire young paleontologists, in the same way Nizar had been inspired by Stromer.

IBRAHIM: We're working very closely with African scientists and we're trying to do this in a way that really results in a kind of win-win scenario, right?

GWIN: Even though dinosaurs are ancient, paleontology is relatively new. Up until the 1700s, Western science didn’t even understand entire species could go extinct. Nowadays, about 50 previously unknown dinosaurs are identified every year, so there’s still a whole lot left to learn.

IBRAHIM: There's so much we don't know. We’re really just skimming the surface. And if a river monster dinosaur like Spinosaurus eluded us for so long, right, I mean, what else have we not found?

GWIN: More after this.

If you’d like to see these fossils for yourself, take a look at Michael Greshko’s story. It’s full of photos of the updated skeleton and animations of what Spinosaurus might have looked like in the water. There’s a link in the show notes.

Spinosaurus is just one of the incredible dinosaur discoveries made over the past few years. Paid subscribers can read our cover story “Reimagining dinosaurs” about how paleontologists are learning more than ever by using advanced techniques like CT scans to examine frozen crocodiles or using lasers to figure out what color Velociraptor eggs were. That’s in the show notes, right there in your podcast app.


Overheard at National Geographic is produced by Brian Gutierrez, Jacob Pinter, and Laura Sim. Our senior editor is Eli Chen. Executive producer of audio is Davar Ardalan. Our fact-checker is Michelle Harris. Hansdale Hsu composed our theme music and engineers our episodes. And special thanks to our guests for recording themselves at home. This podcast is a production of National Geographic Partners. Whitney Johnson is the director of visuals and immersive experiences. Susan Goldberg is National Geographic’s editorial director.

And I’m your host, Peter Gwin. See y’all soon.


Want more?

Michael Greshko has a lot more to say about Spinosaurus. Take a look at his article full of pictures and animations of what Spinosaurus might have looked like in the water.

Or learn about why dinosaurs went extinct in the first place.

You can also make Spinoaurus and other prehistoric creatures appear in your living room by using Nat Geo's dinosaur instagram AR filter. Follow us at instagram.com/NatGeo.

Also explore:

Check out our previous episode about the illegal trade of dinosaur fossils in the United States.

And for paid subscribers:

In our cover story, “Re-imagining dinosaurs,” you can read about how paleontologists are learning more than ever by using advanced techniques like giving CT scans to frozen crocodiles or using lasers to figure out what color Velociraptor eggs were.

The National Geographic Society is committed to illuminating and protecting the wonder of our world. Learn more about the Society’s support of its Explorers.