11 Questions About Stegosaurus
[MUSIC]
[ROGER BENSON appears on screen.]
ROGER BENSON (Macaulay Curator, Division of Paleontology): So I think there is a top five of dinosaurs in the popular imagination,
[An illustrated silhouette of Stegosaurus appears on screen.]
BENSON: and Stegosaurus is definitely among them.
[The illustration zooms out and we see the silhouette of Stegosaurus is standing on a podium in 3rd place. A small teardrop appears below its head.]
BENSON: It’s probably number three.
[A silhouette of T. rex appears on the podium in 1st place, followed by a silhouette of Triceratops in 2nd place.]
BENSON: Of course, T. rex is number one, Triceratops is number two–that’s just my personal favorite–followed closely by Stegosaurus.
[We zoom back in on the silhouette of Stegosaurus. Its name appears in text beside it, followed by the full video title: “11 Questions About Stegosaurus.” The American Museum of Natural History logo appears.]
[A slide replaces this illustration with text: “1. What kind of dinosaur is Stegosaurus?” BENSON reappears on screen speaking. Text appears: “Roger Benson, Macaulay Curator, Division of Paleontology.”]
BENSON: So Stegosaurus is a stegosaur, and that sounds ridiculous, but stegosaurs in general take their name from Stegosaurus,
[An illustration appears where a circle with the silhouette of Stegosaurus pops up in the center, and is surrounded by six other stegosaur silhouettes, which look slightly different. Text appears with a bracket that encompasses them: “Stegosaurs, 170-145 million years ago.”]
BENSON: –and they include other dinosaurs that are generally around in the middle and late Jurassic. So up to about 145 million years ago. And we have fossils of stegosaurs–
[The stegosaur silhouettes scatter over a map of the world, showing that they appear on most continents.]
BENSON: –from North America, from Europe, Asia and Africa.
[BENSON reappears on camera speaking.]
BENSON: And it’s possible in fact that they were present on all continents during the Jurassic.
[An illustration of a stegosaur with lots of spikes appears. Text appears: “Baiyinosaurus.”]
BENSON: Other species of stegosaurs outside of Stegosaurus include–
[Two illustrations of different stegosaurs with spikes on their backs and tails appear. Text appears below each: “Kentrosaurus” and “Gigantspinosaurus.”]
BENSON: –animals like Kentrosaurus or Gigantspinosaurus. But even among stegosaurs,
[An illustration of two Stegosaurus dinosaurs in a bog appears. The illustration zooms in on their back plates, and the spines of a Kentrosaurus appear next to the plates.]
BENSON: –Stegosaurus is different than most other species because instead of having just spines along its back, it has these distinctive plates.
[A new interstitial slide appears, with text: “2. Who would win in a fight: T. rex or Stegosaurus?” BENSON reappears on screen speaking.]
BENSON: People surprisingly often ask me who would have won in a fight between Stegosaurus and T. rex. But they lived 80 million years apart from each other and in fact, they never would have met, sadly. So we’ll never find out.
[LAUGHING]
[Two videos appear side by side: on the left is footage of a Stegosaurus fossil, and on the right is a Tyrannosaurus rex fossil.]
BENSON: Because Stegosaurus lived 150 million years ago,
[Above the footage of Stegosaurus, text appears: “150 million years ago.” Above the footage of T. rex, text appears: “70 million years ago.”]
BENSON: –and T. rex lived around 70 million years ago,
[The video of both dinosaurs appears on a timeline, with Stegosaurus on the far left, T. rex in the middle, and a new video square with footage of the wonders of the world on the far right, representing humans. Text in the human footage appears: “Present day.” Brackets show that the amount of time between humans and T. rex is 70 million years, and the amount of time between Stegosaurus and T. rex is 80 million years.]
BENSON: –we’re actually much closer in time to Tyrannosaurus rex than Stegosaurus was.
[An illustration of a Stegosaurus in a forest appears, with text: “Extinct 80 million years before the mass extinction.]
BENSON: So Stegosaurus was extinct long before the extinction of the dinosaurs 66 million years ago during the K-Pg mass extinction event.
[A new interstitial slide appears, with text: “3. Were Stegosaurus’s back plates used for defense?” An archival photo of Charles Knight working on a sculpture of a Stegosaurus appears.]
BENSON: For a long time the back plates of Stegosaurus were thought to be used in defense, but actually–
[BENSON reappears on screen.]
BENSON: –Stegosaurus evolved from other stegosaurs that have spikes along their back.
[An illustration of two Gigantspinosaurus dinosaurs appears.]
BENSON: It’s very unlikely that those spikes evolved into plates specifically for defense.
[BENSON reappears on screen.]
BENSON: Also the plates are actually very loosely attached to the back, and it’s not clear that they could have resisted the strong forces of a predator coming down on them in some way.
[Close up footage of different Stegosaurus back plates on display.]
BENSON: People have also suggested that the back plates of Stegosaurus might be used in regulating its body temperature. We know they had a rich blood supply because they have traces of nerves and blood vessels along them–
[BENSON reappears on screen.]
BENSON: –that might have allowed Stegosaurus to heat its blood or cool its blood, and therefore regulate its body temperature.
[Visitors walk around two different Stegosaurus fossil mounts at the Museum.]
BENSON: Actually the most likely function of the plates in Stegosaurus is that it was used somehow in display to other individuals of Stegosaurus,
[BENSON reappears on screen.]
BENSON: –so either in mating displays or in displays of dominance,
[Footage of a male peacock shaking its extravagant tail feathers in a display.]
BENSON: –similar to the extravagant feathery displays of some birds today
[A bright green, yellow, and red chameleon creeps by on a branch.]
BENSON: –and similar to the colors, frills,
[A lizard on a branch turns its head to show a large frill behind its head.]
BENSON: –and sails of some lizards living today.
[Illustrations of other types of stegosaurs with spikes appear.]
BENSON: The spikes of other stegosaurs might have been used to some extent in display to other individuals within the same species, but they also could have had a defensive function.
[BENSON reappears on screen.]
BENSON: Because spikes are spiky… and, you know, that might help in defense.
[LAUGHING]
[A new interstitial slide appears, with text: “4. Could Stegosaurus attack other dinosaurs with its tail?” Footage of a close up view of the tail spikes on a Stegosaurus fossil.]
BENSON: So Stegosaurus has four spikes on the end of its tail and you might have heard that this is called the “thagomizer”.
[Text appears on screen: “thagomizer.” BENSON appears on screen.]
BENSON: Now, I’m sorry to let you down, but that’s not the official science name for it.
[The text “thagomizer” is crossed out and replaced with the text “tail spikes.”]
BENSON: We just call them tail spikes.
[Footage of the tail of a fossil Stegosaurus zooms out to show the full body in a defensive position.]
BENSON: But they probably weren’t used to attack other dinosaurs. They were probably used for defense against other dinosaurs.
[A new interstitial slide appears, with text: “5. Did stegosaurs travel in herds?”]
[An illustration of a Stegosaurus in a forest, with two other Stegosauruses in the background. The two other Stegosauruses are crossed out.]
BENSON: Stegosaurs probably didn’t travel in herds. When we find their fossils, they’re often single individuals.
[BENSON reappears on screen.]
BENSON: And sometimes they’re associated with other dinosaurs, like big sauropod dinosaurs. So it’s likely that they aggregated with other herbivores.
[An archival photo of an old Museum display that has a Stegosaurus next to an Apatosaurus.]
BENSON: But it might have been rare for them to form stegosaur-specific herds.
[A new interstitial slide appears, with text: “6. Did Stegosaurus have a tiny brain?” BENSON reappears on screen.]
BENSON: People often say that Stegosaurus had a really tiny brain. And that’s true. The brain of Stegosaurus was about the size of a small lemon or lime. Stegosaurus would not have been very smart.
[LAUGHING]
[An illustrated silhouette of a Stegosaurus appears. Where its brain would be, the illustration of a lemon appears.]
BENSON: But the head of Stegosaurus was also extremely small. So when people compare the size of Stegosaurus’s brain–
[A bulldozer appears over the rest of Stegosaurus’s body.]
BENSON: –to its enormous five ton body,
[The Stegosaurus silhouette disappears and the bulldozer runs over the lemon as it falls to the ground with a splat.]
BENSON: –the brain seems super small.
[A photo of a Stegosaurus skull appears, with the lemon illustration superimposed over it.]
BENSON: In the context of the small skull of Stegosuarus, then the brain is pretty small,
[A photo of a crocodile appears with a drawing of a strawberry superimposed where its brain might be, and a photo of a T. rex skull appears with a drawing of an ear of corn superimposed where its brain should be.]
BENSON: –but not exceptionally smaller than other reptiles.
[An image of the tail and hind legs of a Stegosaurus fossil appears. A circle appears over Stegosaurus’s hips and text appears: “extra brain?”]
BENSON: People also often say that Stegosaurus had an extra brain just at the base of its tail, in its pelvis.
[BENSON reappears on screen.]
BENSON: Now, that’s not quite true. There is an enlargement of the space available for the nerve cord–
[Footage of the tail of a fossil Stegosaurus.]
BENSON: –but that’s not actually a brain. That’s just a large bundle of nerves that’s quite common among other animals.
[A new interstitial slide appears, with text: “7. What did Stegosaurus’s eggs look like?” BENSON reappears on screen.]
BENSON: We don’t know what Stegosaurus eggs looked like. We’ve never found any fossils of them. We do have some very small juvenile Stegosaurus’s,
[A small model Stegosaurus and a fossil on display appear, in the shadow of a much larger Stegosaurus fossil.]
BENSON: –maybe one meter in length, but the actual hatchlings would have been much smaller than that.
[A new interstitial slide appears, with text: “8. Did Stegosaurus have feathers?” BENSON reappears on screen.]
BENSON: Stegosaurus did not have feathers, but it’s not entirely clear that it didn’t have any form of feather-like structures.
[Footage of a small patch of fossil Stegosaurus skin appears. It is bumpy and pebble-like.]
BENSON: The skin of Stegosaurus basically would have appeared scaly,
[Close up footage of crocodile and lizard skin show it to also be bumpy and scaly.]
BENSON: –somewhat similar to a croc or a lizard today.
[BENSON reappears on screen.]
BENSON: It would be really difficult for us to tell if they had just a few fibers on their body,
[Close up footage of the head of an elephant as it shakes its ears. Small strands of hair are visible though they are few and far between.]
BENSON: –similar to the hair of an elephant for example.
[A new interstitial slide appears, with text: “9. What color was Stegosaurus?” Different illustrations of Stegosaurus appear, each with different colored skin and plates–some red and yellow, some brown and black.]
BENSON: We have no direct evidence of what color Stegosaurus would have been. Since we believe the most likely function of the plates was in display, it’s possible that they had interesting colors.
[BENSON reappears on screen.]
BENSON: We have no idea what those colors might have been.
[A new interstitial slide appears, with text: “10. What did Stegosaurus eat?” BENSON reappears on screen speaking.]
BENSON: Stegosaurus ate plants, it was a herbivorous dinosaur. Even the group that Stegosaurus belongs to, the ornithischian dinosaurs, were almost entirely herbivorous.
[An archival illustration of a prehistoric swamp, showing ferns and other ancient plants.]
BENSON: Plants at that time were slightly different to plants today but include many living groups,
[Footage of gingko leaves, a cycad cone, and fern leaves appear.]
BENSON: –things like gingkoes, cycads, and ferns.
[Footage of the skull of a fossil Stegosaurus shows that its teeth only extend partway to the front of its jaw.]
BENSON: Stegosaurus had teeth in the back of its jaw, but a beak in the front of its jaw.
[The skull of a Stegosaurus appears next to the skull of a green iguana, which does indeed have small, flat–but somewhat pointy–teeth.]
BENSON: They’re somewhat similar to the teeth of a green iguana today.
[A new interstitial slide appears, with text: “11. How long did Stegosaurus live?” BENSON reappears on screen.]
BENSON: So we currently have no idea how long an individual Stegosaurus might have lived.
[Footage of one of the Stegosaurus fossil mounts at the Museum.]
BENSON: We have a very limited amount of data on the life history.
[BENSON reappears on screen.]
BENSON: One of the exciting things we’re going to do in the Museum is we have permission–
[Footage shows Apex, a fossil Stegosaurus on display at the American Museum of Natural History, and visitors walking around it and taking pictures of it.]
BENSON: –to cut a sample of the thighbone of Apex, a particularly large, mature individual of Stegosaurus, in order to study the microstructure of the bone, including potential growth rings,
[BENSON reappears on screen.]
BENSON: –a bit like tree rings that are going to tell us about how old the specimen might have been, and also contribute to our understanding of growth and life history of–
[Footage of Apex the Stegosaurus on display.]
BENSON: –Stegosaurus in general by comparing to samples from other individuals.
[Credits roll.
Apex and its associated scientific research and education activations are made possible by Kenneth C.. Griffin and Griffin Catalyst.
Producer
Lee Stevens
Additional Camera
Erin Chapman / AMNH
Lisa Rifkind / AMNH
M30 Productions / AMNH
iStock / aerocaminua, AscentXmedia, ATW Media, BlackBoxGuild, BSPC, loveguli, manode, RosaFrei, viafilms, VisualStories, Wlad74
Images / Archive
AMNH Research Library
Alvaro Keding & Dan Kim / AMNH
iStock / CoreyFord, Daniel Eskridge, hypergon, MR1805, Nastasic, Warpaintcobra
The Noun Project / Bulldozer by Marcus DeClark, Corn by metani septiana, Lemon by Alvida, Strawberry by Juicy Fish
Wikimedia Commons / Brian Gratwicke, Connor Ashbridge, H Zell, Skye McDavid, SlvrHwk, UnexpectedDinoLesson
Music
“Cheery Cinematic Extended” by Gabriel Brosteanu (PRS) / Warner/Chappell Production Music
“Drunk Intimate Extended” by Clive Neal Lukover (PRS) / Warner/Chappell Production Music
“Idiots Cinematic Extended” by Stephen Daniel Lemaire (PRS) / Warner/Chappell Production Music
“Goofy Cinematic Extended” by Gabriel Brosteanu (PRS) / Warner/Chappell Production Music]
Stegosaurus, the giant plated dinosaur of the late Jurassic, is the favorite dinosaur of many people. But that doesn’t mean we don’t have questions–for example, is its brain REALLY that tiny? And what were those huge plates for anyway?
Learn more about Stegosaurus and its fellow stegosaurs as paleontologist Roger Benson explains what we’ve learned from fossils like the recently discovered Apex—the most complete Stegosaurus ever found. These specimens can give us clues into the dinosaurs’ diet, lifespan, size, and natural history.