Well thank you for coming tonight. I'm
going to give you a summary of my last 20 years or so of my research career in
studying dinosaur movement, especially with the focus on size. So dinosaurs of
course are famous for being large and that's what we'll largely talk about is big
dinosaurs and how they handled being big in terms of movement. But it's great to
be here in Seattle, if you're a rock and roll fan, you might well know that
Seattle has a long and proud history but it also has some associations of
dinosaurs and rock and roll including some of the bands. I really love like
Nirvana and Soundgarden, they worked dinosaur imagery into their into their album
covers and posters and so forth. I was an undergraduate student in
Wisconsin back in the early 90s working at a music store when the grunge rock
movement came out and I was like, ah Seattle, Seattle, that's where it's at but
I couldn't get out to Seattle, this is my first time ever in Seattle so I'm really
really excited to be here! Finally I've made it thanks to the Burke Museum. I've
made it to the home of my rock heroes and I hope to present to you some, some
rocks that might be your heroes' rocks that are dinosaurs. Anyway that's a
terrible joke. Speaking of heroes when I was
growing up as as a kid and I see there are some some kids in the audience, I was
really into into monsters in general. It didn't matter if there were science
fiction monsters or dinosaurs to me Godzilla was just as real as t-rex so, so
I was really excited about, about big things in general, King Ghidorah over
there. The three-headed monster was one of my favorites and still is and I think
that fascination in giant things, real and and and not real, just
continued and it explains why I now study them as a scientist, including all
kinds of weird things interesting like fanciful things that could never,
could never work and it's interesting to think why they couldn't work and that
really, when I first learned as a kid that a giant Godzilla just could
not work in terms of the physics of movement it really bummed me out. I was
sad that Godzilla could not really exist because it was too big to walk but
it also made a lot of sense to me so the scientist in my mind began
working when I, when I realized that and thought oh actually even though that
said that Godzilla could not work as a real thing on land that teaches me
something that's valuable. So the work I'll be talking about today is perched
upon the shoulders of many giants, I've worked with a lot of people around the
world. I have to thank a lot of funders there for supporting my research in the
in the UK and other parts of the EU and the Royal Veterinary College I'm based
at. The structure motion lab which is out here just north of London, we have a
lovely campus that occasionally gets a very thin coating of snow that shuts
absolutely everything down for days and days but we also get nice rainbows
landing in campus. And there's our team, we've got a team of several dozen people
who study aspects of animal movement applying physics and anatomy and in my
case evolution to the study of animal movement. So that's where we're based and
a bit about what we do, but yeah today I'm gonna really focus in on the problem
of size as applied to dinosaurs and if you want to talk to me more about this
research after the talk I'm always on social media on Twitter and I have a
blog and so forth, it's easy to find me on the Internet,
I'm all over the place. But here's what I'm going to talk to you about today. I
talk first about the project I began as a PhD student 20 years ago, how fast
could a t-rex move. I'll give you an answer to that question. I'll then talk
about sauropod dinosaurs, the really big four-legged dinosaurs and how their body
shape affected the way they moved as their size changed as well, and
then finally I'll get to a project I'm working on now that I'm really excited
about which is about the earliest dinosaurs, the humble beginnings of
dinosaurs and what made them special, if anything,
and whether that might explain why dinosaurs survived when many other
animals in the Triassic did not survive past the Triassic into the Jurassic. So
that's a quick introduction, here's a little bit about the evolutionary family
tree of dinosaurs in case you're not familiar. We've got three main branches,
the ornithischians like Triceratops, the sauropodamorphs or sauropods is one
group of them, and then the theropods. I'm going to talk to you first about the
theropods which include t-rex of course, then about the sauropodamorphs, that's
their, their cousins as currently understood - although there's another idea
that moves this family tree around a bit that's still controversial. I won't get
into that. Anyway and we've strayed into those theropod dinosaurs so theropods
are great, they're all bipedal, they all walk on two legs, they include birds so
we have a huge size range from hummingbirds all the way up to things
like t-rex. One of the largest land animals that's ever lived especially on
on two legs, up to eight tons or so. So fascinating because in some ways they're
so conservative, they walked on two legs They had a pretty similar body plan but also
because they're so different in terms of size and some features like big tails,
big heads or flights or other features. Now before I get into talking about
t-rex and the movement of theropod dinosaurs, I want to kind of address a
problem, which is how do we reconstruct dinosaur movement at all when all we
have at the beginning are bones. Well I'd like to tell you right away that, that's
not true, we don't just have the bones of dinosaurs. Of course we have footprints,
those are useful as well but even on the bones, there's a lot of information we
can tell about the soft tissues, the muscles, the tendons, the things that make
up us as well as dinosaurs and things that actually generate movement, bones of
course, a skeleton alone cannot move. A skeleton needs muscles and tendons to
drive and support the movement of the skeleton as a system of levers, so on the
bones we can see marks. I've got colored dots on there, these are thigh bones,
femur bones On the left, a crocodile. Here in
the middle is an early dinosaur, here's a little bit later dinosaur, more closely
related to birds, and here's a turkey and this blue dot is one muscle showing it
doesn't move its position very much as we move along the family tree. There's
a red dot that's another muscle attaching to the thigh bone on the side
and that muscle splits into two muscles We can see scars on the bone that are
attachments for that muscle in an early dinosaur, one of them the purple one here
stays put, whereas the other one moves upward onto this big blade of bone that
we can see on many dinosaurs including t-rex and that blade of bone fuses up
here at the top in birds into a big crest that you can see in your
Thanksgiving turkey or chicken or whatever. And so that muscle has come up
to the top of the thigh bone in living birds and and some extinct dinosaurs as
well. So the take-home message is that there is that the bones tell us about
muscles, where they attach and about how the attachments of muscles have evolved
so we can reconstruct the musculature of dinosaurs with some degree of confidence
and that allows us to get one step closer understanding how they moved, if
we can add their muscles and stuff onto them and we can begin piecing together,
what is all this wonderful diversity of bones that we see. This is a family tree
of reptiles with the hip bones inside view, so these are early reptiles, an
alligator here, some early dinosaurs across the middle here up to t-rex,
there's its hip bones and a raptor dinosaur Archaeopteryx, the first bird, a
much later bird, and then a turkey again, showing all the different kinds of
pelvic bones. You can see how the pelvis changes with a few, just a few examples
of the many species that would fill up that family tree. To me an image like
this really raises the question, can we make sense of what these differences
in hip bone structure mean for how these animals would move? How does an early
reptile move versus something like an early dinosaur versus a t-rex versus a
bird. Can we use the anatomy and reconstruct how an animal would
actually work, how it would function and how it would behave, how it would
actually move. How fast it could it move or turn, could it jump, in order to
answer those higher-level questions about behavior we need to start with the
anatomy. Which of course starts with the bones, adds on more information about
muscles and tendons and so forth and that's hard of course, there are many
challenges to do this. There are lots of unknowns about the anatomy, physiology,
how the muscles would work, the behavior itself is often or generally unknown in
many cases. We don't know how living animals work, we don't know how we work, a
lot of our problems we can't fix because we don't understand how we work. So I
went to Stanford and worked with mechanical engineers to learn the
tools they use to try to fix problems that we have with the way we walk, and I
learned those tools to then apply to animals and try to figure out how
do animals work and and then I applied those tools to dinosaurs as I'll show
you a little bit later. But all along the way I've been working throughout my
career on living animals trying to contribute new knowledge on how living
animals work. How do elephants move, how do crocodiles move, ostriches. I've
contributed new information to that as well as studying extinct animals to try
to help flesh out our general understanding of how movement works. When
we do science we always have to balance how many assumptions we make about
things, things we don't know and how complicated are we making our science,
that's always a problem. Do we make very simple models of animals, I'll show you
some examples of that, where my research on t-rex really was
just a few simple equations, or do we make really complicated models where
they're really really realistic, lots of anatomy, lots and lots of assumptions
built into them we have to juggle those kind of problems as
scientists. How do we decide what level of complexity to put
into our research and of course there's always potentially the problem
of, what if dinosaurs broke the rules, what
if t-rex could breathe fire like Godzilla, or what if sharks could shoot
out laser beams from their bodies, fossil sharks as well of
course. If we have no evidence of that we can't ever invoke those kind of
assumptions in science, we have the mantra, the phrase, "extraordinary
claims require extraordinary evidence" We can't say a t-rex had supercharged
muscles that were 10 times as powerful as any other animal that's ever lived,
without evidence for that. So we can't allow for dinosaurs to break the rules
without evidence of them breaking the rules and that's very very important,
it's really a core part of science. And gravity is one thing that didn't change,
one rule definitely that did not change through the history of dinosaurs,
it was only t-rex, was only 66 million years ago. That's nothing, I mean that's
like a few days ago in terms of the history of the earth, gravity has has
not changed much at all, since then, so we can assume the same level of
gravity as today in the time of t-rex or even the earliest dinosaurs. The
solution to all these problems is to be careful, to do science and that's what
I'll be showing you here today. It's easy to look at an animation of a dinosaur
that looks kind of good, we worked with a museum, about 10 almost, 15 years
ago to make this animation trying to show. Here's what as scientists we
thought a t-rex moved like based on the principles of how animals move, some real
science kind of but in the end we realized in making this animation with
an animation expert, this was really just making stuff up, there was almost no
really good science in this animation. It was not really doing what we felt as
scientists was good science, so it made us uncomfortable to
do this kind of animation even though it was useful in showing to the public,
here's roughly what we think a t-rex moved like. we came up with a new approach inspired
by making that animation of t-rex instead of just showing how t-rex
moved which is an easy way to approach the problem, although for us it was
unconvincing, we started with showing how t-rex didn't move so trying to start
with all the ways t-rex might have moved, maybe, and get rid of the ones that just
wouldn't work. This approach just applied the rules of how animals work to
try to say, well is that fairly upright way of moving of a t-rex, is that
possible or impossible, is that really straight legged
way of moving in a t-rex, is that possible or impossible, or is that really
crouched way of moving possible or impossible. We use an approach as I'll
show you to try to figure that out, get rid of things that were impossible or
implausible so we started with a simple leg posed in the middle of a step like
this, so it's just supporting a t-rex supporting itself on one leg like it's
running, so supporting itself on one leg at a time and it has a hip, an knee and an
ankle joint each of which can rotate through 180 degrees so that's a large
amount of movement of each joint and that gives us a big block of movement.
180 degrees of movement of each joint times three different joints, gives us
six million ways we could pose that limb of a t-rex, but of course not all of
those are possible. Some of those six million ways we could pose a t-rex's
leg at one instant in time must be impossible so what can we get rid of
there. Well we applied a bunch of rules of animal movement that we understood
fairly well including, well of course, a t-rex, its joints can only move in
certain ways and we got rid of most of that red space here now colored in
yellowish, most of that was gotten rid of by ways that the limb just could not be
posed in at all without disconnecting the joints and also t-rex
couldn't go through the ground, it was solid, it wasn't a ghost or something, so
positions in which the leg went through the ground. We got rid of those that
helped and so forth until finally get down to the point
where we know t-rex could walk, that's a pretty safe assumption, it could at least
walked so it could support itself with one body weight on one leg at a
time so I could do this and it could at least walk slowly, so our model
accounted for that by getting rid of postures in which the required size of
muscles and other things would be too large in order for a t-rex to actually
support one body weight on a leg at a time, so that little bit of yellow space
that kind of a crouched posture has gotten rid of and then also we asked,
well are there any postures left over in which a t-rex could run and support at
least one and a half times its body weight on a leg at a time, that's a very
slow run that's kind of a jogging sort of force one and a half times body
weight on on one leg at a time is pretty slow, and yes we found some
positions we could pose a t-rex's leg that were feasible and some that were
not feasible that we got rid of and that's what is left over here, 3,000
poses of the beginning, six million are left over as possible slow running poses
for a t-rex, so our analysis using basic math and physics and anatomy allowed us
to figure out that, yeah maybe a t-rex could run slowly with certain
assumptions, we can't get rid of that possibility but we could get rid of fast
running, we couldn't find any solution that will allow a t-rex to run really
really quickly, like forty five miles to an hour but these kind of postures that are
just slightly bent legged but not very straight legged, not very bent legged,
these are all possible postures ways we could pose a t-rex's leg we couldn't
choose between any of those four or any of the of the other 3019 poses in
between them. So that's pretty good that we got that far with that kind of a
simple analysis and overall what we found from looking at a variety of
models of t-rex, and we also took a chicken and made it the size
of a t-rex in a computer model so there is a chicken at about two kilograms of
body mass down here, we scaled it all the way up to t-rex size and found that a
giant chicken at six tons, a chicken would need to have almost a hundred percent of its body weight as leg muscle in order to be
able to move, of course that wouldn't work, chickens need
to have skeletons, they need brains and lungs and digestive systems. KFC might
really love to have a 6-ton chicken but it's just not possible to have such an
organism. But a t-rex, it is of course possible, it's better off, how much muscle
a t-rex would need depending on what kind of assumptions you make. It
would need about ten to twenty percent of it per leg of its body weight to be
muscle that supports the body against gravity and the most muscle any animal
has ever had is an ostrich, right here at that point, right there has about 15% of
its body weight per leg as muscle that works against gravity to support the
ostrich. Humans have nine or ten percent per leg of their of their body weight as
as muscle that helps support us so ostriches are more muscular than we are
and they're the most muscular animal that's ever lived as far as we know, more
muscular than an elephant or a rhinoceros, or a giraffe, a horse,
anything. T-rex, we have no signs that t-rex was more muscular relatively
speaking than an ostrich, ostriches are pretty much adapted to be all, you know,
we're almost pure muscle in many way. T-rexs aren't so much in terms of leg
muscles, they've got a big head with a lot of jaw muscle that does not help
them support body weight. They've got a lot of other features that don't make
them as well adapted as an ostrich's for supporting their body weight. So the
take-home message from this very messy graph is that t-rex was so big, that it
couldn't move very very quickly like an ostrich can. T-rex could run at best
maybe fifteen, twenty-five miles an hour which is around the speed of what humans
can run so that's not bad and it's about as fast as a probably a duck bill or a
triceratops could move at best but it's not as fast as a racehorse or a cheetah
or something like that, so that's what we found out, that was pretty satisfying but
since then we've applied some more sophisticated computer models to our research trying to figure out can we get any better estimates of how a t-rex
could move and we found that better models continue to support what we found
so we do better anatomical models of the leverage of muscles around the joints of
t-rex. We do better models of the mass and the
center of mass is the point at which the weight of an animal, can be abstracted to be concentrated So your center of mass is right around
your belly button, more or less center of mass is very
important, you need to keep your center of mass over your feet or else you'll
fall down. So center of mass determines your posture, if your center of mass is
too far forwards, you can't get your legs under your center of mass and therefore
you either fall down or you walk on four legs which t-rex couldn't do. So that's
very important to know where its center of mass was and we were able to to get
pretty good estimates of that along with other things. So we also looked at how
t-rex grew, there are some nice skeletons of young tyrannosaurs like a
specimen called Jane. That's about ten years old and we were able to estimate
using some computer modeling how big t-rex, young t-rex at about ten years old
was. It was about 600 kilograms, give or take a bit so that's pretty big, that's a
size of a large horse at just ten years of age. Are there any 10 year olds in the
audience? Do you weigh as much as a horse? Well that might tell you something because at 17 years of age, a t-rex
weighed about six tons as big as an elephant. Is there a 17 year old in the
audience anywhere that weighs as much as an elephant? Probably not if
you do some math, it's very difficult to estimate exactly how fast a
t-rex grew but during its teenage years it's very clear a t-rex grew really
quickly. Maybe as fast as five kilograms a
day or about 11 pounds a day, which if you think about that, that's really fast,
that is a lot of cheeseburgers or in the case of t-rex, a lot of duck-billed
dinosaurs and Triceratops. So just thinking about a six hundred to a
thousand kilogram animal that could probably run pretty quickly. It wasn't
very big and thus was fairly athletic. Young tyrannosaurs were really scary
animals, they were hungry, they needed to eat a lot too to grow quickly, and they
were probably reasonably athletic indeed as t-rex grew its legs got relatively
smaller, and its muscles also got relatively smaller, so young t-rex are
pretty leggy, they have nice long legs, pretty big muscles attached to them
whereas an adult t-rex is relatively less muscular than a ten year old
t-rex was. So that really reinforces the idea that the most athletic
t-rex were the teenagers, much like in humans and there's one
muscle in particular attached to the tail and you can see this, if you ever
look at a t-rex skeleton or any dinosaur for that matter matter there's a big
muscle. It's also present in crocodiles and various other reptiles. It runs
from the tail down to the thigh bone, it's called the Caudofemoralis and
that muscle weight is as much as three to six percent of body weight of a t-rex
per leg, so that's a couple hundred kilograms or so of muscle in each leg of
a t-rex. Just one muscle there that help support the leg of a t-rex or the hip, in
particular against gravity so that's a huge muscle, it's one of the biggest limb
muscles ever in relative terms in in any in any animal living or extinct and
that's very impressive, but it was necessary just to support a t-rex. It
wasn't big enough to generate really rapid locomotion in a big t-rex but it
certainly helped young t-rex move pretty quickly and I would not want to
engage in a footrace with with a ten-year-old t-rex. It
would be pretty scary but that's not going to happen. So far I've
mostly focused on extinct dinosaurs but of course there are dinosaurs amongst us,
today we can study ostriches, and this is a computer model of an ostrich that I've
worked with. We do a lot of work, really try to use computer models of living
things to test how well the the models actually work by comparing the results
of a computer model to actual experimental measurements, to see how
well they compare and we found that generally they compare pretty well. So
we're able to predict how an ostrich can move using a computer model and we are
able to measure the same kind of ostrich and see that it matches the
computer model pretty well and that gives us confidence that what we're
doing with Dinosaurs, which we can't directly test, we can't ever get a t-rex
into our lab and put it on a treadmill like we can with an ostrich but we can do the computer models of dinosaurs, extinct ones, but we can do a
lot more with ostriches and other living animals and that's one reason why we
bother. So we've done a lot of those kind of tests to add information. Moving on a
bit, onto the sauropod dinosaurs away from the theropods. We, a bunch of
colleagues and I asked well, how did body shape influence the way sauropod
dinosaurs moved? There were a lot of changes in the shape of sauropods as
they evolved, they started off with pretty short necks and pretty short for
legs and long hind legs, and then of course during their
evolutionary history. They diversified into all kinds of forms, some of whom had
very long necks and tails and long front legs, some of whom didn't but we know
that the earliest sauropodamorphs, the earliest cousins of the true big
sauropods in the Triassic were small and they probably walked on two legs mainly.
But once you get to the Jurassic it's very clear
that the the sauropods were big and quadrupedal, and once you get to the
Cretaceous there's a group of sauropods called the titanosaurs which really
really huge, the largest land animals ever, much larger than an elephant
and they had some changes in their limb posture, some of them even had this
weird, kind of wide gauge posture, when they spread their legs out to
accommodate a really bulky gut so it's been observed that there are a lot of
changes in body shape that might have influenced the way sauropods moved
throughout their history, and we wanted to estimate how body shape changed the
way sauropods moved using computer modeling, and we focused on the center of
mass of sauropods which I've already introduced, talking about t-rex. Center of
mass determines how an animal moves if your center of mass is too far forwards,
you have to shift into moving on four legs, you can't walk on two legs if your
center of mass is closer to your front legs or your head. So we tried to
estimate where the center of mass was using digitized skeletons. Here's our
approach that we used much like we did with t-rex, used various digital
technologies to make 3d skeletons of all sorts of sauropods and sauropodamorphs
added lungs to them and wind pipes and
so forth were able to change the sizes of those, what if they had bigger lungs,
smaller lungs, even if they were missing bones in the neck, we were able to
estimate how long the neck would be based on what was missing and do some
careful analysis of that and even account for, well what if the sauropod
was bigger at the back end than the skeleton suggests or bigger at the front
end. We're able to do a variety of models to give us some kind of error bars for
our estimates of how big our sauropods were and where their center of
mass was and this is the take-home message of that analysis through the
evolutionary history of dinosaurs from early cousins of dinosaurs here, early in
the history, this is 250 million years ago so back in the very very early
triassic, the center of mass is pretty close to the hips, that's what this
number is moving up this way, is closer to the head moving back this way, is closer to the hips so the center of
mass starts off close to the hips, moves even closer to the hips as we get
close to dinosaurs, that's where we have a shift on to two legs from four legs. At
that point in the evolution of dinosaurs and then it goes the other way as we get
into sauropods or sauropodamorphs in the Jurassic, the center of mass
starts shifting further forwards toward the head and fore limbs and then once we
get to the Cretaceous, the titanosaurs do something weird because their body shape
changes a lot but generally their center of mass moves forwards a little bit at
least and we were able to show that these three changes in the evolutionary
history of dinosaurs especially sauropodamorphs relate to changes in body shape,
that in particular in sauropods as their necks got longer, that moved their center
of mass forwards, they're also their forelimbs getting longer, moved their center
mass forwards a little bit - and that was correlated with getting bigger, so
sauropods as they got bigger, their necks got longer their forelimbs also got a
little bit longer and that was related to them, becoming quadrupedal, moving on
four legs instead of two legs around this point in their evolutionary history
so in the early Jurassic or late Triassic roughly. It's pretty
early in the history of sauropods, they became gigantic and four-legged because
of their long neck, you know to a large degree, so that's pretty satisfying. We're
able to show kind of three phases in the evolutionary history of dinosaurs and
sauropods that really show how body shape influenced the locomotion of
dinosaurs in in the early history of dinosaurs, they became better at being
bipedal, then they became worse at being bipedal and shifted to being quadrupedal
and then they became really weird titanosaurs that moved in very
strange ways different from other sauropods because of their very strange
body shape So for the last bit of my talk I'm going
to change gears a bit, I've been talking about giant dinosaurs like the sauropods
and t-rex but now I want to talk about research I'm doing. Right now of course,
all good things must come to an end dinosaurs except birds got wiped out at
the end of the Cretaceous, but let's rewind and think about how dinosaurs got
starts. Dinosaurs got started because of the mass extinction in to a large degree.
At the end of the Permian period, about 250 million years ago, there was a major
catastrophe that almost wiped out life on Earth as we know it, much like there
was a catastrophe at the end of the Cretaceous but much much much worse at
the end of the Permian, and that's what kind of cleared the slate and allowed
dinosaurs to take over on land. So dinosaurs appear shortly after that
major extinction at the end of the Permian and they appear alongside a lot
of really weird animals that look kind of like big armored land crocodiles and
dinosaurs in the late mid, mid to late triassic are pretty
small, many of them kind of house cat size,
not like some of the the big land crocodiles that got to be up to 20 foot
long and armored with big teeth. None of the earliest dinosaurs were like that
really, so early dinosaurs had it pretty rough, they were really lightly
built animals in a very dangerous world with a lot of a lot of nasty characters both plant eating and meat-eating so it's a really weird ecosystem in the
Triassic. I really like the Triassic period because it's so different from
the Cretaceous, the Cretaceous to me is kind of familiar, it's sort of like yeah
kind of like today but with dinosaurs instead of
wildebeest and lions. But the Triassic is nothing like that, it's a very arid
period of Earth's history with these land crocodiles and little tiny
dinosaurs and lots of other weird things. Just really weird, life on land in
general so I wanted to understand the dawn of the dinosaurs and and got some
funding from Europe to do a project called Dawn of the Dinos, we
have a website, Dawn of the Dinos.com that has some nice artwork like this illustrating,
what that time period looked like and some of the characters that were around
at that time. These are wonderful reconstructions by artist John Conway of
some of these critters, like one of those big land crocodiles there and we wanted
to address the question that's been lingering for over 40 years, what
was, if anything, special about early dinosaurs? It's been proposed that early
dinosaurs had what's called locomotor superiority, there was something about
them in terms of their movement that made them better than those land
crocodiles and other things that went extinct at the end of the Triassic
except for the lineage that led to true crocodiles. So were dinosaurs
superior in some way, could they run faster, turn more quickly, jump better, do
something more athletic than those big clunky armored crocodiles could do,
that's never really been tested it's just been either dismissed entirely,
"they're dinosaurs, just got lucky ,there was nothing special about them" or it's been
accepted "oh yeah dinosaurs were great, that's why of
course, that's why they succeeded" But we wanted to test that
idea using physics again, so using the same kind of computer modeling and
Anatomy based approaches I've already shown you, we're just getting started
with that project. Here's an introduction to some of the cool archosaurs, that
group that includes dinosaurs and the crocodile lineage, so the big land
crocodiles and the plant-eating land crocodile type things, there's a living
crocodile and their relationships with various other things including what
looks like what an early archosaur would look like, something like that, like
a small crocodileish thing. There are some of the early dinosaurs that were
not much around that size or even smaller and then we get into true
dinosaurs like that feathered or filamentous, the sauropodamorphs have already talked about and the theropods including birds, so those are
the two main lineages we're focusing on the crocodile lineage, the bird lineage, we're comparing them and different members
of those groups to see what's different about them if anything in terms of how
they can move and we're going to figure that out using the computer modeling
approach, and here we've already started looking at one of them. This is an early
sauropodamorph called Mussaurus patagonicus -- as the name implies it's
from Patagonia and what's really cool about it is, we have a whole growth
series of Mussaurus, so we have a little tiny baby hatchling Mussaurus, that's
why it's called Mussaurus, "the mouse reptile", it looks kind of mouse like and
that's one of the first skeletons that was found, it was one of these little
hatchlings but also there's a 20 foot long adult animal. That's what it looked
like whether it was two-legged or four-legged is uncertain, that's one of the questions we wanted to address and we
asked with Mussaurus, did it the way it moved actually change as it grew,
some dinosaurs just like us we start off on four legs and then move to two legs.
Some dinosaurs did that too, they start off on all fours and then move to two
legs as they grew up, other dinosaurs start off on two legs and they move down
to four legs as they grew up, so what did Mussaurus do, it seemed to change its
body size and shape a lot that adult Mussaurus is about the size of a rhinoceros,
about 1,500 kilograms, 20 foot long, it's a pretty big animal, not much much bigger
than that mouse-sized little hatchling so it changed a lot in terms of its size,
and its body shape changed as well, so we wanted to figure out how its movement
changed as it grew up so there's where Mussaurus is from, it's from the very
very tip of Argentina down here in South America. Here's another little hatchling
right there, beautiful little skeleton, it's actually much smaller than that
picture. Here's a juvenile you can barely see some of the leg bones there, but
that's the hip and the foot is down there, the head would be this way, that's
a couple year old individual from several skeletons that we have from
Santa Cruz province down here in this region of southern Argentina. So we
worked with my colleague Alejandro Otro and Diego Pol to build computer models of the
hatchling, the juvenile and the adult Mussaurus to see what they were built
like, and whether that could tell us how they might have moved, and we also
started by looking at the arms of the adult Mussaurus. This is an
important take-home lesson about dinosaurs, most dinosaurs kept their
palms facing inwards like this, so if you ever see a two-legged dinosaur walking
around like this with its palms facing down, the t-rex is often shown this way.
You point to the person that's showing that and say, you got it wrong, that's
you're showing your t-rex wrong. Dinosaurs mostly have their palms like
this, they could not do this kind of thing like we can do, most dinosaurs - a
few could do this, so they couldn't do what's called pronation and supination.
This kind of motion that mammals are really good at, where we're unusual,
especially humans, at being able to do this kind of a movement but most
dinosaurs could not. They had their arms just fixed like this, could not rotate
their hands much at all, so could Mussaurus, was it able to plant its hands
flat on the ground like this and therefore pronate its hands, or was it
fixed into this kind of a posture? We built a computer model to test that and
that's what this animation goes through, it showed us very clearly there's no way
we could pose the joints of that limb, even taking into account missing
cartilage and other tissues, there's no way we could get that hand to be planted
flat on the ground. It could only keep its palm inwards so that really
supported the idea that adult Mussaurus was bipedal, it could not plant its
hands flat on the ground to be a quadruped so it had to
keep its hands facing inwards like that and furthermore... I'm gonna skip
that, that's not important that's too much text, so we digitally
prepared Mussaurus fossils. This is some work we're finishing up right now,
that's what the actual fossils look like on the left there, after CT scanning
we're able to extract all the beautiful bones from that, from that rock and
here's our computer models - the hatchling, the juvenile, and the adult. That's
relative sizes, really about how big they are, so that's a 20 foot long
adult. It's almost actual size, there on the screen, pretty close, there's a little
juvenile and hatchling, so that's what they look like, we're still adding
the skulls on to them. You can see they're obviously missing from some of
them but we've accounted for them with some simple geometry and what we did was apply some simple computer modeling to add flesh onto the skeletons, like I
did earlier for t-rex and the sauropods with my colleagues. There are two
approaches, one's called convex hull, laying the others called spline based
modeling if you're really into computer modeling, you might care about that.
Otherwise don't worry about it, it's just two different methods, we wanted to see
if they matter, which approach we use, so we apply both methods. Convex
hulling is basically shrink-wrapping a 3D shape onto the skeleton, spline-based
method is adding more realistic anatomy that reflects the the missing
flesh, not shrink wrapping it to the skeleton so there's our hatchling on the
left, in the middle is our juvenile, on the right is our adult Mussaurus,
that's what the the models look like so far, and here's the growth, roughly of
those three models so this is the mass of the animal hatchling is tiny, it's
only a few grams, the juvenile at about one year of age is already eight
kilograms, almost 7.8 there about, and then the adults like I said
is about 1,500 kilograms. Using that method and the two methods agree pretty well
in terms of estimating mass, so again we're using the other method, we get
pretty similar results - about eight kilograms for the juvenile, a little more
than 1,500 for the adult, but yeah with a certain margin of error that's pretty
close, pretty close agreement, and so in 10 years, Mussaurus got to be
over 1,500 kilograms, pretty impressive that it was able to grow that big, that
quickly, though what about its locomotion? Did it change from a quadraped to a
biped, a biped to a quadruped, what can center of mass tell us, well showing
us, very very clearly regardless of what method we used that the hatchling Mussaurus had a center of mass really really close to the the front legs.
Center of mass was up here, well in front of the hips,
no way that a hatchling Mussaurus could have gotten its hind legs under its
center of mass and walked around on two legs at all, it had to have supported
itself in some way on its front legs, but the juvenile in both cases here seems to have been pretty close to being able to be bipedal, and the adults certainly so,
the center of mass of the adult was really close to the hips, and very well
adapted to being bipedal, so that reflects that Mussaurus must have had a
shift during its development from walking around on four legs probably
pretty clumsily, to moving on two legs, probably pretty early in its life, maybe
even by when it's 1 year old it was able to to walk or run around on two legs, instead
of four. So that's pretty neat that we were able to show that with this
approach. And since then we're also working with living animals to
understand how living archosaurs, members of the dinosaur bird and
crocodile radiation, how they actually move, so we've been working with Nile
crocodiles and running them on treadmills. That's a lot of fun, they can
be very stubborn and a little bit bitey but we like them and we also worked
with some little - whoops didn't show that - We also work with some little South
American birds called tinamous which are very primitive birds, they look a lot
like what we think the ancestor of all modern living birds look like,
they're very chicken like, but they're different from a chicken. They are
actually cousins of ostriches and emus and rios,
that's a tinamou right there, the elegant crusted tinamou, there are lovely birds fairly nervous but very athletic, they love
to run, they don't like to fly and that's one reason we chose them, so we've been
working with those animals to see how they move, and here's some example
footage, here's a crocodile. You may not know it, but crocodiles can bound and
gallop, they can use a whole range of gates that mammals can use, that's one
thing that makes crocodiles different from other reptiles, no lizard can do
what you're seeing in this crocodile on a treadmill,
lizards cannot bound or gallop like that, so watch that crocodile, it's moving
its front legs together like this and it's moving, but it's
moving its hind legs together like that it's using a squirrel like gate bounding,
is what we call it technically, it's very similar to a gallop, and that's what
crocodiles do when they want to go really quickly. but they can only do it
at small size - once crocodiles get big they lose that ability, once they pass
about two metres or so in length they become much less athletic and slow down,
and lose their bounding ability. So we're excited to be able to get our
crocodiles able to bound and gallop on a treadmill, and we also used a new
technology that's really powerful to peer inside of crocodiles as they move
and see how their joints actually move. So this is an x-ray video of a Nile
crocodile walking through the video with some markers attached to
the surface of it, so we can track it more accurately. Let me play that one
more time because there's a lot going on there, so we can see inside of it, there's
like, the light space is some of the nasal cavity, you can even see it
breathing if you watch very closely, the lung, the air pipe would be in here,
there's the lung, that's the front leg on the ground, there's the hind leg, the heel,
the ankle right there, and the knee, there's the tail, all the vertebrae of
the tail, and you can even see the microchip the vet implanted into it.
There's the microchip, a lot of beautiful detail in in that x-ray video of that
crocodile walking through our experimental setup.
So this is called x-ray reconstruction of moving morphology, it's changed our
whole field now instead of looking at animals from the outside, like in that
last video, and guessing how the skeleton is moving. We're actually now
able to measure how the skeleton is moving with a very very high level of
accuracy, which helps our computer models and other methods be more accurate, and
allows us to do better science, basically it's totally transforming how we study
human movement, animal movement, everything, and it's actually at various
hospitals, they're using it now as well to look at our knees and shoulders
and other parts of our body to study what goes wrong with our joints and
their motions, so we're using this to study animal movement. So to wrap up
that's just a teaser of that Dawn of the Dinosaurs project, it's going on for
the next three and a half years, we'll be showing a lot more on our website,
dawn of the dines.com but I've gone through three projects with you here today, going
from the dawn of the dinosaurs to the dusk of the dinosaurs with titanosaurs
and t-rex, the earth-shaking giants and the not so earth-shaking early
dinosaur. The giants live in extreme, where gravity really really dominates
the way we they live, big dinosaurs everything about their body, and a t-rex
and in a sauropod, really to me as a scientist,
screams the influence of gravity much more. So even in that, than in a human
we're pretty big and gravity influences us a lot, but the way gravity
influences us is nothing like it is compared to how it influences a
sauropod, an elephant, a t-rex a rhinoceros, other big things, gravity - as
you get bigger it influences the way you work, in drastically different ways as
you get bigger and bigger and bigger. I'm sure adults in the audience can
sympathize with that too, compared to how we were when we were younger and lighter,
but big animals needn't be simply walkers. So I've shown you some examples
with t-rex where there's potential for diversity to evolve, so t-rex need
only to have walked, maybe t-rex could have run slowly, it couldn't have run
quickly, I think most of my colleagues have probably convinced a few holdouts.
They're still always going to be some holdouts that disagree with me, but I
think there's a general consensus nowadays that t-rex could not run very
very quickly, might have been able to run slowly or walk quickly, we're not
totally sure because there's a lot of uncertainty there in those computer
models, different sauropods move differently because they had a different
center of mass, different body shape and so forth, titanosaurs move differently from
early sauropods, things like Diplodocus or Mussaurus, sauropodomorphs
themselves showed a shift during their growth from quadrupedal to bipedal like
Mussaurus. I showed that toward the end of my talk and why did early dinosaurs
get dominance across the Triassic - Jurassic, around 200 million years ago,
well we still don't know, I don't know, I have no real horse in that race, I
just like to have an answer to that long-standing question and you can watch
that website and find out how we're doing with that research or follow me on
Twitter or ask some questions if you have any questions at this point. Thank
you very much! Yeah so I'm going to start with one
question which is for John, which movie do you think actually best depicts motions and dinosaurs To be honest I still really love how
Jurassic Park depicted movements in dinosaurs for a large part, especially I
really like their t-rex, and a neat story there with the way their t-rex moved is,
if you go back and watch Jurassic Park, when the the t-rex is chasing the Jeep,
watch how that t-rex moves - it always has one foot on the ground, in fact mostly it
has two feet on the ground, never goes airborne and in fact I talked to the
animators who made Jurassic Park and they tried to animate t-rex going 4050
miles an hour ,as some paleontologists argued it did and it looked ridiculous,
they thought they said it looked like the roadrunner going off a cliff, the
legs were going so fast they slowed it down, so it just goes boom boom boom boom,
it was only going 15 to 20 miles an hour so that's pretty bit close to what I
estimated t-rex could do, and so that's an interesting case where art and
science have come to more or less the same answer, they just felt like yeah
that didn't look right the audience wouldn't believe it, for it to move
quickly and and the science reinforces that ,okay so other end of the spectrum
how fast do you think Velociraptor could run, yeah, smaller dinosaurs could move
more quickly, especially medium-sized, so as you look at any land animal, in
general the speed of the animal as the animal gets bigger through evolution
starts off pretty slow, so small animals are not very fast, a mouse can be outrun
by a house cat for example, and then speed goes up as animals get bigger and,
then the optimal size for being fast is around thirty to fifty kilograms, so like
cheetah, greyhound, racing hare or something like that is the best size to
be for being fast, and ostrich is pretty close but then as you get bigger speed,
goes down, so big things even horses are slower
than smaller things, rhinoceros is, giraffes, hippopotamuses, elephants are
all slow because they're large so a Velociraptor would be moderately fast, we
don't know exactly how fast but probably pretty good, I wouldn't want to
race it! I don't know if you've ever had this question before, but could a t-rex
hop? Yeah I get that question a lot, it's a good one, we have no tracks
of any extinct dinosaur hopping, that's one thing and we have lots of tracks
of them walking and running but hopping is actually really really hard, it's the
worst way to move if you want to go quickly
unless you're small, so kangaroos can hop because they're not too big, but big
kangaroos like a red kangaroo at about a hundred counter kilograms at top speed,
is very very close to to rupturing its muscles and tendons, the kangaroos are
close to the biggest a hopping animal can possibly be, and still hopping is
really hard to do, it's about twice as hard as running at the same speed, so you
can try it try hopping and try running and see what you can do more quickly.
You'll be able to run more quickly than hop, hopping is terrible for a big animal
to do and if a t-rex tried to hop, it would break its legs so I can guarantee
you. So a couple times you mentioned in the talk, of the age of these dinosaurs
and the question here is, how do you tell the age of a dinosaur years older than 20 years old? I didn't explain that and that was very naughty of me. We can, the best
way is, you can take sections of bones and Chris's lab does a lot of this,
take a section of the bone just like you take a section of a tree and count the
rings in the tree or the bone, there are growth rings there that allow you to
estimate how old a dinosaur was, if it's a well-preserved bone you can count that,
so come to Dino days tomorrow and you can see some slides that show that kind
of stuff and talk to people that actually study that because I don't do
that myself. I work with colleagues that do it and know how
to determine the age of a dinosaur, that's really the only precise way to
figure it out. So moving away from the carnivorous dinosaurs,
Pachycephalosaurus was bipedal, can you say anything about its locomotion? It
was bipedal, yeah, again moderate size to moderate to
medium largest size dinosaur, so it was moderate speed more or less, I haven't
studied it so I can't give more detail to that but I doubt it would give us any
big surprises in terms of its movement it would be pretty much as we'd
expect. Zoey has a question here, she wrote her name, how long do you think
t-rex could maintain a running pace? That's a really hard question, endurance,
we just don't know from fossil remains there's no easy remain, no easy method to
calculate fatigue or endurance of an animal from the skeleton or
computer model, the science just is not that far along, no one's figured out a
way to answer that question, so Zoey if you are or if you become a scientist
maybe you can figure that out because I'm at a loss, we just don't know. Okay to
a little bit more lighthearted questions, and then we'll finish up.
First of all classic question, what is your favorite dinosaur? Well I have to
say Trex is one of them but because I've worked on t-rex and it's
cool I admit, but I also, the only dinosaur ever discovered was a little
tiny bird-like dinosaur called an alvarezsaurid from the Hell Creek
Formation of Montana, it was in a museum drawer at Berkeley and I discovered a
little bit of its hip bone and in the hip bones were so distinct, I knew
exactly what it was and they're really cool animals, they're only about this big
with stubby little arms and long tail and there were feathered
really cool things that people think, maybe dug in ant hills because they had
these big stubby arms and little tiny heads with very sharp needle-like teeth.
I still don't know what they did there, they're mysterious animals but they're
they're really really cool and the fact that I I found a piece of one that I
didn't get to name but at least it's some sort of new animal from Montana,
that makes it one of my favorite dinosaur. Oliver age 7 asks the
question, what's your favorite rock band with dinosaurs? Oh there aren't that many and there's t-rex, there's
dinosaur jr., there's - what else is there - anyone else, dinosaur rock bands
there's probably some death metal bands with dinosaur names that I'm not
thinking of. Is there an Allosaurus? I can't think of any,
I mean t-rex is alright, and Dinosaur Jr is a cool grunge band, they're not from
Seattle they're from Amherst. So that's, that's not great but I like them alright!
Let's thank Jon one more time!
World-renowned Tyrannosaurus rex expert Dr. John Hutchinson shares the latest research on how dinosaurs moved, and how their walking and running changed over time—especially as they evolved into sizeable giants.
Learn why Tyrannosaurus rex was not a fast runner, and how living cousins of extinct dinosaurs and computer models help us understand how dinosaur movement worked.
Recorded at Kane Hall at the University of Washington, March 2, 2018.