Dinosaur Dancing and Movement
44:26 Share

We've reached 10 years of podcasting this year. To celebrate, we're mailing Allosaurus patches to all of our Dino-it-alls at the Triceratops level and up. Join by February 28th at patreon.com slash inodino to get your exclusive Allosaurus patch.

Hello and welcome to I Know Dino. Keep up with the latest dinosaur discoveries and science with us. I'm Garrett. And I'm Sabrina. And today in our 524th episode, we're talking about dinosaur dancing and movement. Yes.

We also have dinosaur of the day, Valdosaurus, and a guanodont that lived in the early Cretaceous. And our fun fact is that bony ridges in sauropod tail bones may have helped them use their tails as a weapon or to signal to other sauropods. In other words, some sort of movement. Mm-hmm. And we are still on parental leave. We are...

recording this early so we're actually expecting our second baby soon but it seemed like a good idea to record a few episodes ahead of time they're unpredictable sometimes they show up early yes so it's good to have these things ready in advance since we already have a toddler it was a little bit too difficult to record enough to have weekly episodes this time

So we are trying out biweekly, but don't worry, we will be back soon. And in the meantime, I hope you enjoy this episode on dinosaur movement. But before we start talking all about dinosaur dancing and movement, we have some patrons to thank. And this week they are Anna Rose, Amber, Travis, Michael, Fia, Linda, Claire, Jurassic Pirate, Larissa, and Mary.

Thank you all very much for joining and keeping our dinosaurs moving and dancing. Yes. Yes. Thank you so much for your support. We appreciate you always, but we especially appreciate it while we're able to take some time off for our growing family.

Yes. And I really enjoy going into the Discord server when we're having a lot of other distractions. It's a good place to relax. So if you'd like to check out our Discord server or join this amazing group of people, then please consider joining our Patreon at patreon.com slash inodino.

Well, if all goes according to plan, and I think it will, this episode will be coming out just at the beginning of the new year. So happy new year. Hey. Hey, yeah. And I was thinking about how one of the most common new year resolutions is to exercise, which is what got me thinking about dinosaur movement. And also I was thinking about dancing because there's a lot of dancing that happens on New Year's Eve. Probably not for us this year with the newborn and the toddler. Yeah.

But who knows? We might be dancing to get them to sleep. Yeah, that's true. Bouncing. Yeah. Rocking. I am saying this a couple months ahead of time. We can try. Anyway, this episode's about dinosaurs dancing, which is really about courting and mating and also about how they moved in general. But real quick before we get into that, I have another New Year's item.

So the last couple of years, we've been celebrating the new year with a special Dino-Doll patch, and we're doing it again this year. And this is also an extra special year for us because we're celebrating 10 years of the I Know Dino podcast.

So if you join our community at the Triceratops tier or above by the end of this February, we'll send you an exclusive Allosaurus dino it all patch. Yay carnivores. Yeah. First time we're doing a carnivore. Yes. Or if you're already a patron, make sure your address is up to date so we can send you your patch. And that's again at patreon.com slash I know dino. So happy new year.

I would say it's really hard to know how dinosaurs moved since we mostly know them from their bones and some trace marks. Yeah. Occasionally you get some muscles and skin and fat, collagen that gives you some hints at how their bones were connected, but often not. Often you're just working with the bones. Yes.

So it's hard to know how they moved. It's even harder to know how they danced, I'd say. But there is some evidence of some dinosaurs dancing, at least. We just don't know the choreography. I see. There was a dinosaur dance floor discovered in 2008 on the Arizona-Utah border in the U.S. What do you mean by dinosaur dance floor? There were so many tracks, as well as some dinosaur tail drag marks.

Okay, so this isn't like a constructed floor. This is more like a dinosaur dance area. Yes, it's not like a disco or something like that. A club. I can say something more modern. Okay, but this was it was a sandy desert oasis 190 million years ago.

But like I said, it includes some rare dinosaur tail drag marks. There's fewer than a dozen dinosaur tail drag marks found around the world. And these marks, they're like two and a half, almost two and a half inches wide and up to 24 feet long. There's more than a thousand dinosaur tracks. There's probably multiple thousands, which is why they called it a dinosaur dance floor.

There's probably multiple types of dinosaurs that made the tracks. There's at least four species, and they found tracks from theropods, small, medium, and large theropods, as well as sauropodomorphs. And these animals ranged from adults to juveniles. Surprising that it's so many different types of animal. Me too. I'm guessing it didn't all happen at the same time. But the scientists compared it to Dance Dance Revolution because there were so many tracks.

Oh, like all the arrows in a row. Yeah, all the stomps. Originally, these tracks were thought to be potholes from erosion. They were made in what was a wet, low watering hole between the dunes.

But now scientists consider them to be tracks and not potholes because they're the right size. They're limited to a single rock bed. There's four types of footprint shapes that are seen repeatedly. One third of the prints are surrounded by small ridges or mounds from stepping in wet sand. The tracks show a direction of travel to the west and southwest.

And there's signs of overprinting where a dinosaur would have stepped in a footprint. Yeah. So it's kind of like a double exposure in photography. It's a double footprint on top of itself. Mm-hmm. Double footprint. Anyway, there was a 2024 study by J.A. McLarty and R. Esperante that studied the theropod tracks that showed the dinosaurs turning between 44 to 84 degrees.

Four trackways in eight sites are found with stopping or pausing points. In one case, one of the dinosaurs was limping. In another case, there's a sudden abrupt change in direction. It's possible it was responding to an unknown obstacle and then it returned to its original orientation. So maybe it was a dinosaur that was avoiding another dinosaur that was in motion. And there's a trace that shows a possible theropod crouching, which is pretty cool.

So it sounds like that one isn't any sort of actual dancing. It's more of a, they call it a dance floor just because there's so many tracks. Yes. But you see the movement and you see unusual movements because usually we just see the walking. So I guess we can't officially rule out dancing. Yeah. But maybe the simpler explanation is more like avoiding obstacles and things like that. Maybe.

Maybe. Like I said, we don't know the choreography. So we have talked about trace fossils before in previous episodes, and there are a lot of tracks that have been found around the world. Another big one is the Carreras Pampa track site in Bolivia. That's not the vertical one, but it's from the late Cretaceous. It's the world's largest concentration of dinosaur trackways. They found 978 trackways so far. Wow.

So it's probably a lot of individuals making these tracks. We don't know exactly how many, but they're made by theropods of various sizes. The track lengths range from almost three inches to almost 13 inches or a little over seven to almost 33 centimeters. They're from theropods, different sizes, anywhere from over 29 centimeters to 1.3 meters or over 11 inches to over four feet at the hip.

Usually, like I was saying, we see tracks where they're walking in a straight line. But apparently for this one, there's some evidence of tail dragging and swimming, although it's a work in progress. So we don't know the details yet. So maybe some of the tail dragging is like getting into or out of the water or something like that. Could be. But there is evidence of theropods that were dancing in that they were probably doing some like mating or courtship dances. Yeah.

In 2016, Martin Lockley and others published on these scrape marks. There are about 50 of them found in sandstone from 100 million years ago in Colorado. And the scrapes are up to two meters in diameter and they're backward scrapes. So maybe it's from lecking. Like the males are performing a mating ritual to attract females like we see with grouse. Yeah, there's a lot of birds that do that kind of thing. Mm-hmm. So maybe grouse is the best analogy for really scraping into the dirt. I think so.

Now, Acrocanthosaurus lived nearby at the same time, so maybe it's from Acrocanthosaurus. Yeah, he's has two meters in diameter of a scrape. It's very large. That's almost seven feet. Yes. And they run in five and six foot patterns and they resemble traces that are left behind by courting birds. So the team actually compared them to puffins and ostriches. The thinking is the traces were made in breeding season in springtime and

There's four sites with large nest scrape display traces identified, and that helps support this mating dance idea. And then in 2024, Rogers, C.C. Bunton, and others found more evidence for mating displays or nest building behaviors. At Dinosaur Ridge in Morrison, Colorado in the U.S., there's scrapes along with ancient microbial mats, invertebrates, and plant traces. Specifically, there's two large symmetrical troughs with 30 sets of scratch marks that preserve toe marks.

There's sharp vertical walls of individual scratches, which may mean the area was moist to water undersaturated when the marks were made. It's not good conditions for a nest. And then behind the troughs are microbial mat chips and fragments, and the mat chips were ripped off by theropod's toe claws. The microbial mats and good preservation from a second generation mat shows that the marks were made in spring, probably before the breeding season. So all seems to point to mating dances.

Yeah, I think I remember reporting on this way back in the day and looking into what the lecking displays are like and everything. And like you were saying, one of the big pieces of evidence is not that there is something specific about one of those scratch marks, but that there are just a whole bunch of them in one location that fossilize together. And what you see with lecking and some of these birds today is that there will be a bunch of males in the same general area trying to get attention of a few females.

So the fact that they're all doing it together is significant, sort of like the earlier version of dinosaur nesting sites where you find a whole bunch of eggs in the same area kind of shows you that they're possibly doing some sort of courtship and mating in the same area. This is just another piece of that story. Yeah. So then that brings me to mating. We don't really know how non-avian dinosaurs mated.

There's no direct evidence that's been found, no fossils found of dinosaurs in the act, for example. We do think they probably had cloacas, like modern birds. We do. It's all of the above whole. If it was similar to crocodiles and birds, it probably was a quick process. We do know a lot of dinosaurs had ornamentation, possibly to attract mates, like horns and frills or feathers or crests.

There is evidence of maybe one mating pair of dinosaurs. They're known as Romeo and Juliet. They're a pair of Oviraptorosaurs found in 2011, specifically their con. That was our dinosaur of the day back in episode 290. I think they also went by Sidney and Nancy. Sid and Nancy. Sid and Nancy, yes. I like Romeo and Juliet better. Romeo and Juliet, yeah. Especially because they got fossilized together.

Yes, they were found in the Gobi Desert. They died and were buried together. They died after some sudden rains, which caused our sand dune to collapse on them, probably. Just like the fighting dinosaurs. Yeah. But these were lovers, not fighters, potentially. Right. They run the gamut in the Gobi. They had feathers, but they didn't fly, so it seems like the feathers could be for attracting mates. They were also about the same size, same build, probably around the same age.

Based on some fused vertebrae, they are thought to both be adults. But one of them had large bony structures in the tail, which might have been to support muscles used for tail feather displays, like modern peacocks. And the one with the muscles for tail feather displays was probably male. And then the one with the smaller bony structures was probably female, because then it would have had more room or it would have been easier to lay eggs.

The tail was flexible and muscular, so it could shake its tail feathers to attract mates in theory. And Scott Persons and others ruled out that it was a pathology on the tail. They said the structures were too different to be individual variation as well. But it's so hard to know. Yeah, sexual dimorphism from just two individuals is hard to say for sure. But that's really cool. Mm-hmm.

Now, in terms of how dinosaurs moved, just in general, Ray Harryhausen, who's a famous animator, wrote, quote, I found dinosaurs to be the ideal subject for stop motion animation. The fact that nobody knew how those huge reptiles had moved or, for that matter, exactly how they looked meant that I could bring them alive without any fear of criticism. Oh, how times have changed. Maybe he just wasn't aware of how critical paleontologists could be at the time. Yeah, or...

You know, we know a lot more now than we did when he was animating. That's true. In 1841, Richard Owen envisioned dinosaurs as standing and moving more like mammals and birds than sprawling reptiles based on studying their limb anatomy. Like their joints seem to keep them in this erect posture and restrict limb movements to a plane parallel to the body. This is known as parasagittal gait.

Yeah, I think that mammalian look is a good description of what he advised for the Crystal Palace dinosaurs, where they kind of look like big bears. It does, yes, especially that Megalosaurus. But then people started thinking of dinosaurs as sluggish and dragging their tails until the dinosaur renaissance in the 1960s and 1970s.

Paleontologist John Hutchinson, who's done a lot of research around dinosaur locomotion, said way back in 2005 that to figure out how dinosaurs moved, we need to know more about their biology. You gotta focus on their entire limb, not just the bones, and also look at the tracks and other evidence they left behind. So we do know based on models made from dinosaur skeletons and footprints that dinosaurs had an erect posture, and the limb motion is mostly from the hip.

We'll get more into how dinosaurs moved in just a moment, but first we're going to take a quick break for our sponsors. It's your last chance to get your limited edition Allosaurus patch. Fun Allosaurus fact, there is evidence of Allosaurus cannibalism. It's unclear if Allosaurus killed each other or just didn't pass up on an easy meal. It's also unclear if they hunted cooperatively or if they were just drawn together by something and ended up fossilizing together.

But either way, Allosaurus was an amazing and ferocious animal. We chose to make our Allosaurus patch black and red to match its intensity, and I wouldn't be surprised if Allosaurus had actual red accents on its head to impress potential mates.

It certainly had red teeth like our patch after a good meal. Yes, and if you want to see the new Allosaurus patch, head over to patreon.com slash inodino. And while you're there, if you like what you see, you can join our Dino It All community. If you've already joined, just make sure your mailing address is up to date. If you sign up at the Triceratops level or above, you'll get your very own Allosaurus patch. Just make sure that you join by February 28th.

Again, to check out the new Allosaurus patch, sign up to get your own, or update your mailing address, head over to patreon.com slash inodino. As you write your life story, you're far from finished. Are you looking to close the book on your job? Maybe turn a page in your career? Be continued at the Georgetown University School of Continuing Studies. Our professional master's degrees and certificates are designed to meet you where you are and take you where you want to go. At

One thing that would have affected how dinosaurs move is whether or not they were more warm-blooded or cold-blooded. A 2022 study found that ornithischians were more likely cold-blooded and sauropods warm-blooded, although a study in 2024 found the opposite. Ha ha ha!

Those are such recent studies to be on completely different pages. Yes. The 2024 study found that the three main dinosaur groups, theropods, sauropods, ornithischians, adapted differently to changes in temperature, and that the ability to regulate body temperature evolved in the Jurassic about 180 million years ago. They looked at fossils from a thousand species, and they also looked at a

And they found that theropods and ornithischians seemed to spread to live in colder climates in the early Jurassic. So maybe they evolved endothermy, where they could generate their own body heat, be warm-blooded. Those groups are adaptable, and they did well in various climates. There are theropods in warm and dry climates, as well as cooler and more seasonable climates. And there are ornithischians that went to more humid and seasonal climates.

Sauropods, though, stayed in warmer, lower latitude areas and not just for the food. The thinking is that they were more cold-blooded. Otherwise, they would have overheated and needed to eat more food than even was sustainable. That's true because cold-blooded animals don't need nearly as much food because they're not turning all that food into heat for themselves. There is some debate on this and some debate on whether there's a sampling issue, like which dinosaurs were included in the study.

On the other hand, it seems sauropods would have shed too much heat in the neck alone if they were in cooler climates. Oh, that's interesting. Yeah, because even if you're warm-blooded or cold-blooded, your body shape makes a big difference. Like, you look at things like penguins that are so round. Yes. And with humans, too, right? Our limbs tend to get shorter as we're closer to the poles over time than when we're near the equator. Yes. So maybe this will be an ongoing debate for a while. Hmm.

There's been a lot of studies on dinosaur movement, and I think it makes sense to break it down by the three main groups, starting with the theropods. Models come in really handy for these studies. There was one done by Pasha A. Van Bilhurt and others found that two-legged dinosaurs use their tails when walking.

The questions they asked her, what's the preferred walking speed and what's the optimal walking speed? And they found that for T-Rex, it's under three miles per hour, which is similar to humans and other animals like ostriches, horses, elephants, giraffes, news and gazelles. They are all between 2.2 to 3.1 miles per hour. This natural walking speed minimizes the amount of body energy spent walking.

So the study predicted a slower walking speed than other studies for Tyrannosaurus. But anyway, they also found theropods used their tails while moving. But the tails were supported and stiff. They were suspended by ligaments that behave like rubber bands. And it made them like a mass spring system or a suspension bridge with lots of muscle in it. The tails did have some flexibility. They would move back and forth with each step.

What they did was they made a computer model of the tail based on Trix the T-Rex, which is about 39 feet or 12 meters long, and gave it a walking speed of 2.86 miles per hour. They didn't look at the max speed, just the optimal speed. Yeah, a lot of times it's easier to find that optimal speed because you can look at the spacing of tracks, you can sort of do a calculation on like the pendulum of their leg, or you can look at range of motion and all sorts of things to that effect. But for your

Looking at the maximum speed, that's so much more complicated because then you're talking about maximum range of motion and you probably don't have tracks of it running. So you're going to have to infer that from a whole bunch of estimates on where muscles and ligaments would be, how flexible joints would be, how much cartilage there is. It's much more complicated. Yes.

There are other studies that have found that on the max speed size, it could go up to like 12 miles an hour and 18 miles an hour or 20 to 29 kilometers per hour. Any faster than that and the bones may have shattered. Yeah. So in that case, you're looking at what's the limit of the bone strength, which is one way to look at it, but not all animals get close to that. Yes. It's not often the limiting factor that you're going to break a bone if you run any faster. Sounds painful though.

Don't go too fast or you'll break a bone. Yeah. Anyway, this isn't the only study that looked at a dinosaur's tail. There was one in 2021 by Peter Bishop and others that made a computer simulation of Coelophysis. That's a theropod that lived in the Triassic. It's on two legs. It had long legs and a long, heavy tail. And it's really well known because a lot of fossils have been found. So that made it easier to build this model.

And they found that its tail helped it walk and run because it wagged its tail side to side, similar to how we swing our arms when we walk. And so it's possible other dinosaurs did this too. So the tails are important for movement, not just the legs. Yeah. And the tail kind of wagged to the left when the left leg retracted backwards and then wagged to the right when the right leg retracted backwards.

When the model forced the tail to wag in the opposite way, they found the dinosaur had to move differently in a way that took more energy. Yeah, it's like if you ever walk and try to swing your arms with the leg that's going forward, it feels really awkward and weird. Yes. But the cool thing with the tail is that it has those muscles that attach to the back of the leg. So that swing to the side literally pulls up the leg using the caudal femoralis muscles. So...

They get this extra sort of pendulum effect of the tail going from side to side and this rhythm to their walking that we don't get to take advantage of. I mean, I guess our arms do a little something, but it's not as efficient. Yes. And they also found that it used more energy without the tail. So the tail is important for movement.

There was another study in 2020 of coelophysis that simulated it running and found that it had a more upright posture than modern birds around the same size. So probably used a more upright or extended leg posture instead of using a more flexed hip when running fast. A study in 2018 by Bishop and others compared ground running birds to predict how bipedal dinosaurs moved based on their speed and body size. So the model did require knowing an animal's body mass and speed.

And they examined 12 species that ranged in size from 45 grams to 80 kilograms or one and a half ounces to 176 pounds. It's quite a range. And then they recorded them moving at different speeds on racetracks. So these are living animals. They included quails, tinamoos, ostriches, emus, and turkeys. They found birds move in a continuum from walking to running. They have a really smooth transition.

Yes, they're not like us where you can really feel the difference as soon as you go from walking fast to jogging and that one leg's getting off the ground. They do this thing called fast walking, which is like an exact in between. I'm always amazed if you ever chase a bird or see somebody chase a bird, they keep one foot on the ground and just their feet are going back and forth so rapidly before they finally get to an actual run. And a lot of them switch to flying these days without ever really running. It's more just a faster and faster walk.

Yes. Yes, another study from earlier in 2017 found that their step width decreases as the speed increases, so the feet get closer as they speed up, and that the step width decreased gradually with dinosaurs and birds.

But for us humans, it changes abruptly, sharp and sudden when we're switching from walking to running. So we have distinct walking and running gates. And you can easily tell the difference when we're doing either of them. Yeah, it could be partly why it's so hard to find running tracks of dinosaurs. Because maybe you look at a track and you're like, that's a regular walking track. But it's actually a running track and it's hard to tell the difference.

Yeah, and when the birds keep their feet on the ground at the same time, it's called intermediate gait of grounded running. Grounded running. Yeah, I've heard it called fast walking before, but I guess grounded running is good too. Yeah, and other theropods did the same as birds. Birds are theropods, but non-avian ones. Usually we think of running when all feet are momentarily off the ground, but there is an updated definition I found, which is bouncy locomotion. Yeah.

So with dinosaurs, they were striders. They walked one foot directly in front of the other. Bouncy is an interesting thing because it's like what part of the body needs to bounce. Because when we run, it's like our whole body bounces. But if you watch something like a cheetah or something, they're almost more like curling up and then stretching out. And it really looks very smooth. When you see a slow motion of it, their head is pretty steady. And even their back and stuff doesn't go that high. It doesn't really bounce per se. But to say a cheetah isn't running would be crazy. Yes.

Although that 2018 study found that T-Rex would have moved in a more bouncing like way. It kind of happened at the bigger sizes is a little bouncier. It does often seem like birds are able to do some of that fast walking or grounded running because they're so small. Getting those really tiny thin legs to flip back and forth really quick is a lot easier than getting hundreds of pounds of leg to do the same thing. Yes. Yeah.

Well, as you can imagine, there's been a lot of studies that compare birds to their non-avian ancestors, and that makes sense. You can infer how dinosaurs moved based on looking at birds. For example, a study in 2010 found that ostriches use their wings to help break quickly, turn, and zigzag, which might mean that dinosaurs like Gigantoraptor use their feathered arms to help them maneuver and keep them stable.

Think of it like a jet plane. It's like they put a flap down and it grabs a bunch of air. So they turn really quick in that direction. The same thing with an ostrich sticking out a wing. Yeah. They also found in ostriches a small intertarsal muscle that's important for movement. Oh, in the middle of the foot. Yeah. So if non-avian theropods had it, they could have had similar running styles and that could mean it took less energy to run so they would have been able to run longer and faster.

There also seems to be a link between wing size and function. Emus and cassowaries have small wings, they hold them tight to their body, and don't use it in locomotion. Interestingly, a 2021 study found that early dinosaurs moved differently from birds, which also makes sense because things might change over time. They used 3D computer models to see how 35 leg muscles evolved over 230 million years, and they found that the hip and knee muscles changed.

Large carnivorous theropods that use two legs to walk in the early Jurassic evolved some special muscles that made their leg joints more mobile and might be related to taking on larger prey. But this reversed in birds. So early dinosaurs may have moved more like mammals than birds. Maybe Richard Owen was right in some ways.

Oh, and last, just for fun, I wanted to bring up, we've talked about this before, but that 2015 study that got the Ig Nobel Prize, that's for work that makes you laugh and then think, it was research done by Jose Iriarte Diaz on dinosaur movement, and he attached a fake tail to chickens to see how it affected their walk.

He used modeling clay to attach the tail, a wooden stick, to chickens two days after hatching, and he worked on 12 chickens. It was described like putting a plunger on their butt, which is basically what it looked like. It did. And he would change the tail every five days as they grew, and then compared their movements to chickens without tails.

And suggested that dinosaurs walked with a vertical stance and most of the movement in the hips, more like humans. But the chickens without the plunger tails had more horizontal movements with the knees doing most of the work. Yeah, that goes back to that. The tail helps a little bit with balance and things like that. Yeah. Even if it doesn't have the muscles there to lift a leg, it can still help to just have that weight. So that covers theropod movements.

I don't think there's as much research on sauropod movement, but there are still some interesting studies. A lot of them involve scanning fossils and making computer models and simulations to figure out how they walked. One study in 2017 found that Musaurus, which was our dinosaur of the day in episode 220, it's a sauropodomorph that lived in the late Triassic in what's now Argentina, and it was originally thought to be small, but it turned out those were based on juvenile skeletons. We now know it could get much bigger.

Anyway, it moved on two legs. At least at some points, right? Yes. The study found that the palms of its front limbs faced inwards and its arm joints couldn't rotate downwards. They compared the front limbs of crocodiles and musaurus and reconstructed the musculoskeletal anatomy and then compared the range of motion of the arms. They looked at 30 muscles around the shoulder, elbow, and wrist joints. And it turns out that limb posture plays a big role in muscle action, how the muscles work.

Crocodiles have a range of locomotion closer to the, quote, presumed ancestral state for Arcusauria. I mean, they haven't changed much. They found that Musaurus could maybe have some active pronation of the hands, but the muscles around the joint to actively pronate may have been too weak. Hmm.

Based on Musaurus, it seems that sauropods moving to all fours was linked not only to mannus pronation, how their hands were, but also by the four limbs shifting into a more columnar posture. So they had to be able to hold all that weight. Yeah, and that's easier if you put your legs under you. I mean, I guess the alternative is you just rest your whole body on the ground and have them sprawled out. But then if you're trying to cover a lot of distance, it's a little tricky. Yes.

Then a study in 2019 looked at the growth series of Massospondylus to figure out how it changed its movement over its lifetime. Massospondylus was our dinosaur of the day in episode 40. It was a sauropodomorph that lived in the early Jurassic in what's now Argentina. And we know them from hatchling, juvenile, and mature specimens. So you can compare a growth series and see how it changed over time. Yeah, I love that. That we have sort of the cradle to grave relationship.

growth curve of massospondylosis so rare. Yes. So for the study, they compared body shape and locomotor stance being on four legs versus two legs and how it changed over time from hatchling to juvenile, about one year old, to adults, which are over eight years old.

They found massless spondylitis grew quickly from about 60 grams or over two ounces to about seven kilograms or over 15 pounds just at one year old. And then over a thousand kilograms or 2,200 pounds as an adult. And during this time, their body center of mass shifted from mid-body to more in the back, nearer to the hips. So this helps show a shift from being quadrupedal to bipedal. And it happens early on.

They found the development of the tail and neck was more important, too, in determining the sauropodomorph's stance. There was another study that reconstructed how sauropods walked based on studying their tracks. There were three trackways, and they measured the distance between them as well as figured out if the print was from the front or the back foot, as well as the left or the right leg.

They found the sauropod walked in a diagonal couplet pattern, keeping one foot down on each side, and it moved more like a beaver or a hedgehog. Yeah, I think that means front left, back right, simultaneous, and then front right, back left, simultaneous. Whereas a lot of other animals sort of do them in a rotation, where it's like front left, front right, back right, back left, or vice versa. Yeah. All the way around, especially the big heavy animals. Yeah.

Yeah, so the sauropods didn't move like giraffes, because giraffes have either the left or right legs hit the ground at once. Oh yeah, that's the other one. You do both on the same side going forward. Yeah. Both on the other side going forward. But that would have been too risky for a sauropod in case it fell down, because it's such a large size. If it fell, it would probably die. Although it's possible that different sauropods walk differently. Definitely.

Almost certainly when you're talking about sauropodomorphs over 150 million years, they're not all going to walk exactly the same. Yes. I mean, even like you're talking about with Musaurus, they started out quadrupedal, switched to bipedal. We don't think all sauropods did that. Mm-hmm.

And then last but not least are the ornithischians, the bird-hipped herbivorous dinosaurs. There's a lot of those with different types of movement. Oh yeah, lots of variety because you've got things like ankylosaurus, triceratops, pachycephalosaurus, and much more. All the hadrosauroids. But a 2011 study found that the earliest ornithischians were small bipeds, small and walked on two legs, and they used their arms for grasping.

and that three Ornithischian lineages independently evolved to grow large and walk on all fours. But speaking of the bipeds, the two-leg walkers, two-leggers, it's got to be a fun nickname. Anyway, there was a 2013 study of Psittacosaurus that found it was mostly bipedal as an adult. It shifted from all fours to two.

They studied 16 individuals from the Yixian Formation in China. 10 were juveniles. And the forelimbs and hindlimbs were close to the same lengths as the hatchlings. But as it got older, the limb lengths changed and it became bipedal. So it seems like this shift happened sometime after its third year, based on histology. When it was young, it's possible the Psittacosaurus hatchlings were mostly on all fours and ran on two legs. And then adults were only on all fours when moving very slowly.

but it seems there was at least a limited shift in posture. So maybe the hatchlings used their long arms to help keep them stable, especially on substrate or when moving slowly. A 2023 study looked at the range of motion of forelimbs in Styracosaurus and Thesilosaurus. They looked at the shoulder motion, orientation of the humerus, the radius, the ulna, and both had limited range of motion at the shoulder.

They found that Styracosaurus, which is a centrosaurine, was like other chasmosaurine ceratopsians and moved with its elbows tucked in at the sides, and it could splay its forelimbs. It also was very front-heavy and walked on all fours.

For sure. You'd think most of those ceratopsians with the huge skulls would be stuck on all fours because the back legs are going to be on the ground, the actual legs historically for dinosaurs. It's just a question of whether or not the front legs slash arms are off the ground. And if you've got a skull that's seven feet long and weighs hundreds of pounds, it's going to be hard to keep that up off the ground. You have to support it somehow. Yeah. And they had pretty short tails too, so there wasn't much of a counterbalance happening.

Mm-hmm. In the sprawling position, Styracosaurus could raise and lower its torso and head and then rock. So maybe it did that for some head-shoving contests and rock side to side, and it could have moved in a way for display and then also for the head as a weapon. Thesilosaurus, on the other hand, had limited humerus motion and couldn't swing the humerus forward, but its forelimbs or hands could contact the ground while it stood.

It's unlikely that the salasaurus watch on all fours, though, because its palms face toward the center or middle. So there we have it. Dinosaur mating and dancing and dinosaur movement in general.

So a lot of evidence, a lot of different approaches you can take on it from models of what the trackways tell you in combination with the bones to sort of logistical issues of just how much different parts of the body weighed or how much stress like a T-Rex leg could take while running. Mm-hmm. The actual direct evidence, like you were saying, the scrape marks. Oh, I hope there's more scrape marks found. Love the idea of dinosaurs dancing. Mm-hmm.

We will move on to our Dinosaur of the Day, Valdosaurus, in just a moment. But first, we're going to take another quick break for our sponsors. And now on to our Dinosaur of the Day, Valdosaurus, which was a request from PaleoMike716 via our Patreon and Discord. So thanks! It was an iguanodon or nithopod dinosaur that lived in the early Cretaceous in what's now England, in the Isle of Wight.

It's described as somewhat kangaroo-shaped. It walked on two legs, it had shorter arms, a long tail, a bulky body, and a small head. And it's estimated to be about 13 to 16 feet or 4 to 5 meters long.

The holotype is the femora, the upper leg bone, and it was 14 centimeters or five and a half inches long. So it's estimated that its body was 1.2 meters or 3.9 feet long and that it weighed 10 kilograms or 22 pounds. But the holotype's a juvenile. That is small. Maybe it should be described as wallaby-sized rather than kangaroo-sized. Maybe wallaroo. We don't know how big an adult would have been, though. That's true. Yeah.

Valdosaurus is considered to be a dryosaurid. Dryosaurs are iguanodons that lived in the Middle Jurassic to early Cretaceous in what's now Africa, Europe, and North America. And as a dryosaur, that means it would have had a beak and probably been a fast runner based on limb proportions and muscle attachments. No skull of Valdosaurus has been found, but it probably had a battery of teeth. The type species is Valdosaurus canaliculatus.

The genus name Valdosaurus means strong in Latin. It comes from the Latin volus, wielden, which refers to the wielden group where the fossils were found. So the genus name means wield lizard. The species name Canalicolatus means with a small channel in Latin, and it refers to a groove in the thigh bone. The Reverend William Darwin Fox collected two small thigh bones on the Isle of Wight

and in 1868 suggested that they came from the same individual, an iguanodon found in 1848 by Gideon Mantell that was renamed in 1869 as Hypsilophodon. Both femora, or thigh bones, were referred to Hypsilophodon. Then in 1975, Peter Galton named the thigh bones as a new species of Dryosaurus, Dryosaurus canaliculatus.

And then in 1977, Galton named Valdosaurus based on these two thigh bones. So he changed his mind. In 1982, Galton and Philippe Taquette described a second species, Valdosaurus nigeriensis, but this is now considered to be Alrasosaurus. William Blows named another species in 1998 as Valdosaurus dextropata by including that name in a list, but it turns out that was an error and there was no description of it, so it's a nomonudum.

Meaning it wasn't officially named, so don't bother using it. Yes. Being closely related to Dryosaurus, which was found in the US, led most Dryosaurid fossils found in Europe being referred to Valdosaurus. But in 2009, Peter Galton reviewed the Valdosaurus material and found no fossils from outside England could definitively be referred to Valdosaurus. And even of the specimens found in England, it was unclear if they were all Valdosaurus.

At one point, there were some individuals thought to be found in Romania of Valdosaurus. There were about 3,000 disarticulated bones, and some of them were small ornithopod bones, and they thought those were Valdosaurus.

More Valdosaurus fossils, four more specimens to be exact, were found in 2011 from the Isle of Wight, which shows that it was more abundant than previously thought. Because I guess those 3,000 bones, they weren't all Valdosaurus. And maybe none of them were Valdosaurus. There was a new skeleton found in 2012 by Nick Chase, described in 2016. It's the most complete one found so far. It includes part of the backbones, an almost complete tail, parts of the hips and both legs.

So it's an articulated skeleton from the mid-back to the tip of the tail, but it's missing its front half, possibly got eroded away. Oh, erosion. Yeah, I getcha. Comes for us all. Some other dinosaurs that lived around the same time and place as Valdosaurus include the Tyrannosaur Eotyrannus, Spinosaurus, Sauropods, and Ornithopods, including Iguanodon, Hypsilophodon, and Mantellosaurus.

And other animals that lived around the same time and place include fish, turtles, crocodilians, and pterosaurs. And for our fun fact, like I said at the beginning of the episode, bony ridges in sauropod tail bones may have helped them use their tails as a weapon or to signal to other sauropods.

There was a 2024 study that found bony ridges in the neural canals of sauropods, as well as two theropods, a thyreophorin, and a hadrosaur. A neural canal is a space or system of spaces in the vertebrae that forms the canal of the spinal cord, and the spinal cord passes through the neural canal tube. So it's related to the nervous system and can tell us a bit about an animal's movement and behavior.

larger neural canals can mean more nervous system tissue in that area. And if, for example, there's more nervous system tissue in the arms, that can mean the animal used its arms more compared to animals with less nervous system tissue in the arms.

Yeah. If you're having a difficult time imagining where the neural canal is, it's basically in our vertebrae, we've got the round part with the discs that some people call them, where you feel like slip a disc. That's what's shifting. That's what the cartilage is in between and all that. And then there's the neural arch that on us is facing outwards from our back on dinosaurs at faced up. And in between those two, there's a gap.

And in younger dinosaurs, those two bones aren't fused yet. But in older dinosaurs, just like in older humans, those fuse completely together, making an actual canal covered in solid bone on all sides. Yes. So you're saying that there's bony ridges in those canals.

Yes, and the authors started this study because back in 2020, the scientists who described the sauropod Abderranerus found bony ridges and suggested that they were neural canal ridges in the tail bones.

So they looked at a bunch of dinosaurs, Cediosaurus, Haplocanthosaurus, Apatosaurus, Diplodocus, Camarasaurus, Brachiosaurus, Brontomyrus, just to name a few of the sauropods. But then there was also Allosaurus, Ceratosaurus, Stegosaurus, and an indeterminate Hadrosaur. Covering all the dinosaurs. Yeah. They found that the bony ridges were only in the tail bones, in the caudal vertebrae, and that they're long and they vary in size and position.

Similar bony ridges have been found in some modern rayfin fish, lungfish, and amphibians, and they're known to be bony spinal cord supports. So it's unclear what the dinosaurs were using these bony ridges for. But in sauropods, maybe it helped keep the spinal cord stable while moving the tail, especially as a weapon or for signaling to other sauropods. With all of these dinosaurs, the tails are anchored to paired catofemoralis muscles that retracted the thigh bones while walking and running.

So maybe the stresses on the tail from moving were enough that it needed these spinal cord supports. Or maybe they were for, what did you say, display or weaponry? Or signaling, yeah. But in any event, it would be an anchoring point for those things. Not that the dinosaurs could see the small bit of bone deep inside the neural canal of another dinosaur's tail. True, true.

And that wraps up this episode of I Know Dino. Thank you so much for listening. If you want to keep up with weekly dinosaur content, we do have a newsletter that's going even while we're out for parental leave. You can sign up at inodino.com. Stay tuned. Next episode, we're going to have an interview with Dean Lomax, plus our bird-like dinosaur of the day, Aristosuchus. Sounds very fancy, like an aristocrat. It does.

Thanks for listening, and until next time.

If you want to help us reach our goal and also help us continue to make the podcast, please head over to patreon.com slash inodino. Again, that's patreon.com slash inodino. And a huge thank you to everyone who joins and has joined.