So as well as looking at real fossils, I'm also interested in
trying to understand what extinct creatures were like as living animals.
One way to do that is to create digital computer models.
You can control all sorts of features in them, like their density, their shape
and proportions, and you can do experiments on the computer
to see, could extinct animals from the past do things that people have suggested.
Could they swim? Could they jump? How fast could they run?
How strong were their bones? Things like that.
But to have anybody believe what I say about extinct things, I also have to
be able to show that my methods work for living animals.
So I've developed a whole series of models for large mammals and living
reptiles today to test my methods and I can show people
my method works and then I use the same method for the extinct things.
I am going to show you an example of flotation and buoyancy and stability
in animals. I'm going to start with the alligator, because that's my test animal.
Then I want to show you what I find for Spinosaurus.
People want Spinosaurus to be this aquatic, swimming dinosaur but
there's a whole bunch of problems with it, and I'm going to show you
here one of the problems when you put Spinosaurus in water.
I am going to show you the 3-D alligator model first.
Here's a view of my static alligator model. It's a full three-dimensional mesh
and I've assigned different tissue densities to different parts of the body.
The average density of an animal is about one gram per cubic centimetre,
which is the same as water, but to properly simulate a real animal
you need to include some air spaces.
This is a lung and this lung volume is based on observations of real alligators.
It represents about eight or nine percent of the total body volume.
I can calculate all sorts of forces acting on individual slices or within slices
to see what would happen if you put this model into water, and what forces
are acting on it, and how will it balance, and how will it become stable.
This is my simulation of the alligator model.
What happens when you put it in water.
I like to imagine I've held it under water with my hands and I tip the head down,
take my hands away really quickly, and what happens?
Buoyant forces are lifting it up. This is with a full lung.
You can see the final stage at around frame 21.
You can see the dry surface at the top, and the darker wet surface.
I published this in a scientific journal and people were happy that my method can
accurately represent what a floating alligator looks like at the surface of the water.
If I couldn't show this for the alligator, people wouldn't believe what I said for dinosaurs.
Here's my Spinosaurus model.
There's been talk that Spinosaurus was a fully aquatic, swimming, diving dinosaur.
A first, and it's very unusual.
I developed this 3-D model based on the most recent reconstructions.
Again, I put a lung in there to make sure it was a proper animal, and also, theropod
dinosaurs have systems of air sacs throughout their bodies, starting from
just behind the hips and running all the way forward into the neck.
That air displaces tissue and makes these animals very light.
You have to wonder, what happens when you put a really light animal in water?
Is it going to float, or is it going to sink?
Spinosaurus floats like a cork. This is with full lungs.
The people that want Spinosaurus to be a swimming, diving dinosaur want the
animal to stay underwater swimming at a constant depth, but I've even deflated
the lungs down by 60% and this animal still floats.
It is because of this system of air sacs in their bodies that Spinosaurus could
not stay underwater without great effort. There's another problem, I won't show it
here, but it actually rolls over onto its side, it is unstable.
I've also done as a check, I've also developed a 3-D model of
an Emperor Penguin, which is a very aquatic theropod, but it still has to
come onto land, and I can simulate what a floating penguin does perfectly accurately.
I think that should give you confidence that what
I predict for the Spinosaurus is reasonable.
With my computing and math skills I can go beyond the bones a bit and
try to understand more about what these animals were like as living animals.