Dino 101: Dinosaur Paleobiology is a 12-lesson course teaching a comprehensive overview of non-avian dinosaurs. Topics covered: anatomy, eating, locomotion, growth, environmental and behavioral adaptations, origins and extinction. Lessons are delivered from museums, fossil-preparation labs and dig sites. Estimated workload: 3-5 hrs/week.
Field Work
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Del curso dictado por University of Alberta
Dino 101: Dinosaur Paleobiology
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De la lección
Death and Fossilization
This module describes how fossils form, how we interpret the taphonomy of skeletons and bonebeds, and looks at the possible biases taphonomic events may create in the fossil record.
Conoce a los instructores
Philip John Currie, PhDProfessor and Canada Research Chair, Dinosaur Paleobiology
Department of Biological Sciences
Even if a dinosaur bone or complete skeleton becomes perfectly preserved,
there are many factors which may prevent it from being excavated and
moved into a museum for all to see.
This is often the case that a perfectly preserved skeleton becomes exposed and
is available for an easy excavation, but it might be in a place that nobody visits.
Essentially this perfect fossil is never found.
The fossil would then disintegrate during modern times through
the same weathering processes that didn't destroy it 70 million years ago.
A sad situation, but very plausible.
Let's say the dinosaur skeleton was found at the top of a really steep cliff
that we couldn't get to.
Sometimes skeletons are too difficult to get out of the ground for
the resources we have available or
maybe, our skeleton is there, but hidden under the pavement of a city.
A few years ago in Edmington,
a sewer maintenance crew found several dinosaur bones.
After a bit more looking around in the sewer, they found a few more.
However, because they found the bones far in the ground beneath a built up area,
they couldn't excavate to find anymore.
Perhaps a hungry predator found the dinosaur’s carcass
before it could be buried and then the predator ate all the bones.
Result, no fossil.
Finally, it may have been the case that a dinosaur died in an area where there was
no chance, its carcass could be buried, like in a forest or on a mountain side or
a dry desert.
The bones would have slowly broken apart and weathered away.
>> Well that's enough talking about how dinosaurs bones are not
preserved because here in Dinosaur Park,
we have literally millions of dinosaur bones exposed at any one time.
The majority of the bones are things like this.
They are just isolated vertebrae, bits of limbs, parts of limb bones, fragments.
They don't give us a tremendous amount of information about the animals and
they can also be very hard to identify because they've gone through these
processes where before they got fossilized, they may have been eaten by
another dinosaur or tumbled in a stream for many years before they got buried.
And then of course, once they've been eroded, they break up relatively quickly.
However when we walk around,
we also find a lot of isolated bones like that that are more interesting.
So for example, this is a tooth of a Trinosaur and
the Trinosaur is called Gorgosaurus.
We find many teeth in Dinosaur Provincial Park and that's because dinosaurs shed
their teeth throughout their life and in that way, they're very similar to sharks.
And so you can find that one animal could produce probably thousands of its teeth
in its lifetime and of course, they have a very good chance of being fossilized
because the enamel on the outside makes them quite hard.
Now a specimen like this can be identified, in some cases, right down to
the species level and consequently, we will take this back to collections.
When we find a fossil that we feel should go back to our collections, for example,
this ornithomimid,
or ostrich mimic toe bone, we have to record information about the specimen.
We'll take a little specimen card, and on the specimen card,
we'll mark a field number, and the identification is ornitha myabitombo.
The age of the formation, right here, is the dinosaur park formation, so
that'll be filled in too and the locality is recorded in most cases, using a GPS.
And the GPS gives us information about the latitude, longitude, or
any other system and the altitude that the specimen is found on.
The information is then taken back to camp and
each night is transferred into a database, which is returned to the university.
Finally, the specimen is wrapped up so that it can be transported safely.
>> Here we are at the Dannick site.
It's located just inside the city of Edmonton,
only a short drive away from the University of Alberta.
What we have found here are many different bones from several dinosaurs.
Phil, what can you tell us about the site?
>> That's a great question.
Bonebeds like this one, are in fact, massive accumulations of bones of many
individual animals usually at a river channel, but not necessarily, and
those bones normally represent long term accumulations of bones that
have washed downstream in the river and
then been dropped in places were there's quiet water.
And as a consequence of that, very often,
they represent animals that lived in the region for hundreds or thousands of years.
But here we have something different because all of the bones belong to
one type of dinosaur, an animal called Edmontosarus.
Edmontosarus is one of the giant duck-billed dinosaurs.
We have at least 15 individuals here.
When we look at the bones in this bone bed, we can see that
the animals probably died together at exactly the same time and
they were buried very shortly after.
Interpreting the bone bed like this is one of the many things
that paleontologists do.
Let's talk about rocks for a moment.
In this quarry, the dinosaurs are being found in something called mudstone,
silt stone or a shale and these rocks are very fine grained and
they represent quiet water environments.
They're the kind of environments like marshes or swamps where the mud settles
out very slowly and buries the dinosaur bones over a long period of time.
Most of our dinosaurs in Alberta that are skeletons are found in sandstones.
This is a chunk of sandstone from Dinosaur Provincial Park and
this particular specimen has a leaf fossil on the back of it.
But sandstones are much coarser grained, and
it takes more energy in the water to move the sand.
And so this represents a channel deposit in a river, and
that means that when a dinosaur came to the bottom of the river,
it could be buried very rapidly by sand and so the preservation
is very different than what we find in this bone bed where it was quiet water.
This is one of more than 700 dinosaur quarries
in Dinosaur Provincial Park where dinosaur skeletons have been excavated.
And in this situation, there were two phases to this quarry.
We found the quarry first in 1982 when there were a lot of bones sticking out
the edge of the hill and we realized we had a dinosaur skeleton.
However, as we investigated further, we also realized that it had been dug up
once before and that in fact, the skull had been taken away.
Because the skull was gone and because the skull is the thing we use to identify
the specimens most readily, we decided we would not take the specimen until much
later, when we found out that in fact, the skull was in our own collections.
It turned out that in 1920, George Sternberg, who was working for
the University of Alberta, had collected the skull and
left the rest of the skeleton.
Now this turned out to be a very important specimen,
something we call a type specimen which is the one that bears the name for a new
species and because it was a new species, we decided that the skeleton was so
important that more than 20 years after we found it, and almost 100 years
after George collected it, we came back here to collect the rest of the skeleton.
The process is pretty much the same now as George used.
It hasn't changed that much over the years.
George had to deal with a lot of overburden, so from the edge Up there,
he had to remove the overburden using heavy tools.
Probably a pick, a shovel.
And maybe even dynamite.
Once he got down to where the skull was, he had uncovered the skull.
He knew what he had.
He collected it and sent it to the University of Alberta.
In our case, we had a lot less overburden to deal with.
Because George had taken most of it away.
But still, we had to remove all of this to get down to the skeleton.
Which was at this level.
Once it was uncovered, then of course we knew how much of the skeleton we had.
And what we had to ship back to the university.
As we get closer to the specimen of course, we change our tools.
George was using, as I said, pick, shovels, and dynamite.
We were using geological hammers, awls, and chisels.
And once we got very close to the bone, we were using dental picks, needles,
and brushes.
Most of the good work though is done in the University, not here.
Because the season is too short.
So, we capped it with plaster and burlap and shipped it back to the university.
Now, the rocks in the dinosaur park are generally pretty soft.
And we normally take about three weeks to collect a dinosaur here.
However, it's not that good in other parts of the world.
So for example, in Antarctica,
I encountered some of the hardest rocks I had ever worked on in my life.
We had to use heavy tools all the time.
Including dynamite, rock saws, jack hammers.
And yet, the process was the same.
It just took a lot longer.
>> Miriam has found an Edmontosaurus rib and ischium.
Which is part of the pelvis.
Now, when we find something in the quarry, we use a notebook to record various
kinds of information about the bones that we have found.
We also use a grid here.
Which is a meter by meter square that is broken up into ten centimeter segments.
We use this to create a map that accurately depicts
where the bone is located within the quarry.
These two bones have been completely uncovered now.
And they're ready to be taken out.
The technique we'll use is very similar to what doctor's have used for
a long time to protect a broken arm or a broken leg.
That is, they use plaster and burlap.
Or more recently, something called gypsona, to wrap the broken arm or leg in.
And we do the same for the fossil bones.
Essentially, the idea is to provide a hard protective shell to protect the bones.
So that they don't fall apart.
Before we put the plaster on though, we'll cover it with wet paper towels.
And that acts as a separator.
So the plaster does not stick to the bone.
Once the plaster hardens, then all we have to do is turn it over.
Remove a bit of the rock.
And put plaster on the other side, as well.
So that it's protected for the journey back to the laboratory.
Now that the plaster is dry, we're going to put a number on this jacket.
And it's a unique number that'll also be put on the maps.
So we can always tell where the bones come from in the quarry.
Now it's time for the fun part of hauling the heavy jackets back to the truck.
We are very lucky here.
Because the bone bed is quiet close to the road.
Sometimes, this can be very hard work.
And we often need to use helicopters to haul the jackets out of the field.
And bring them to trucks that are quite far away.
The specimens make their way back to our laboratory, at the University of Alberta.
Here, you can see volunteers and
technicians removing extra rock from the bones, using dental picks and brushes.
If the bones are broken, glue and putty are used to put them back together.
Sometimes, it is easier to identify what bones you have and
what species they are from, once all of the rock matrix has been removed.
Sometimes, a rock is too hard to remove using picks, alone.
So we use a special tool,
called an airscribe, which is like a tiny jack hammer.
The technician, Clive, worked slowly around the bone to avoid damaging it.
Preparing fossils can take a long time.
And is detailed, painstaking work.
You need a lot of patience to do it.
But the rewards speak
for themselves, once you have a complete, prepared skeleton.
[NOISE] Finally,
each specimen receives an official record number in our catalog of fossils.
And it is stored in our collections.
It is then available for someone to study it.
Or it may be prepared for public display.
There are many dinosaur fossils in the university's collections.
And this is, in addition to many other fossil vertebrate bones, kept for
creatures like fish, mammals, turtles, and crocodiles.
So far from the Danek bone bed, we have
collected almost 1,000 different bones from Edmontosaurus and Albertosaurus.
And these are organized in cabinets and on shelves.
So that they can easily be located for research.
The Danek bone bed mostly contains the remains of the hadrosaurid Edmontosaurus.
Which is fitting, since the site is located in Edmonton.
We found quite a few bones at the site.
And we're pretty sure we have several animals buried here.
We want to try and get account of just how many dinosaurs we might have.
And for this, we can count the bones in the quarry.
Here's a quick inventory of the numbers of some of the types of bones we have found.
What is the minimum number of animals that died in the bone bed?
A) 10.
B) 15.
C) 67.
Or D) 100.
When we try to count the number of specimens, we use a unique element.
In this case, the left femur.
Because each animal only has one left femur,
we know that every one we find represents another animal.
Because each skeleton has many vertebrae and teeth, these elements are not
very good ways to estimate a minimum number of individuals in a bonebed.
So the correct answer is B, 15.
>> This bone bed contains many individuals.
And those individuals are different sizes and different ages.
So for example, we can look at this bone.
Which is a very large upper arm bone, from Edmontosaurus.
This bone is the same bone.
Another upper arm bone.
But this is from a much smaller individual.
Now we know from comparison with other skeletons.
And work that we do on the thin sections of the bone themselves,
that this represents an animal that was probably three or four years old.
And it would've weighed about as much as a cow.
This one, on the other hand, is in the range of 20-25 years old.
And it weighed about as much as an elephant.
The vast majority of bones that we find in this bone bed are Edmontosaurus.
And most of those bones are fairly complete and easy to identify.
However, mixed in amongst those whole bones are many fragments like this.
And one would wonder why we bother to pick up fragments which are essentially
unidentifiable.
Other than the fact they're Edmontosaurus.
But when you look at them,
they tell you a lot of information about what happened here.
So for example, this bone has this nice spiral fracture on it.
That's the kind of thing that happens when the bone is still fresh.
Old, dried bones don't break that way.
And that tells us that something happened here.
And the clue is accentuated by this mark, right here.
Because, that is a tooth mark that was made by Albertosaurus.
Now, as the tooth chip dragged across the bone, it would leave that mark.
But very often, the teeth, in fact, penetrated the bones.
And broke them and left those spiral fractures.
The teeth themselves are the second most common thing we find in this bone bed.
They make up about 5% of the bones we find in the bone bed.
And these teeth are kind of special too.
Because the Albertosaurus teeth that we find here don't have the roots.
The roots are gone.
And what that tells us is that these teeth were in the process of being shed.
Just like when we lose our baby teeth, the roots get reabsorbed.
And we have a loose tooth.
It was the same for Albertosaurus.
The time when these loose teeth fell out most commonly was when they were feeding.
When we have a tremendous amount of evidence here to show that
after the Edmontosaurus died.
The Albertosaurus came in here and scavenged on them.
And that gives us information about what happened, perhaps.
These are the quarry maps.
Each one represents one square meter at the bottom bed.
And when we look at the quarry map.
What it tells us is the size of the bones.
It tells us how they're associated with each other.
It show us where they are in the quarry.
And it gives us a sense of the orientation.
Now, if this was a fast water situation that the animal's been buried in,
all of the long bones would be lined up in the same way.
But they're not.
They are lined up in different ways.
They cross over each other.
That confirms that this was a quiet water situation.
that the bones were buried in.
We look at all the evidence we have from the maps.
From the bones.
And we can come up with an interpretation.
We can see, for example, that after the Edmontosaurus died,
as a herd, at the same time and the same place.
They were scavenged by Albertosaurus.
The bones were torn apart, in many cases.
And everything got mixed up.
So, it's hard to find two bones of the same animal in the same place.
Overall though, even though we can tell what happened after the Edmontosaurus
died, we sill haven't answered the question of what led to their death.
And the reason we come back here, year after year.
Is we're looking for clues that might tell us
that these animals died in a drought around the marsh, for example.
Or a pond.
Or that, perhaps, there was a forest fire that killed them.
Or maybe they died of a disease.
Those kind of clues are very hard to find.
And we keep looking for them.
Big problem is that,
in any paleontological excavation as we work them, we answer a lot of questions.
But for every question we answer, we seem to create far more questions.
That we have to go a little bit deeper after that.
>> In this module, we've learned about the techniques for finding and
excavating dinosaur bones.
We've also learned how to interpret some of the geological and
taphonomic features of bones.
We know which sedimentary environments are more likely to preserve fossils.
We know to look for things like bite marks, disarticulation, and broken bones.
And we know how to record information at a bone bed quarry.
At the the "Danek" bone bed,
we've only uncovered bones from dinosaurs that already have names.
However, sometimes we get lucky and
find the bones of a new, previously unknown dinosaur specimen.
As the discoverer, we might even get to name it.
But how do we know that a particular specimen is, in fact, the new dinosaur?
And how do we name it?
We'll cover these questions later in the course,
when we learn the concept of the species.
Next, however,
we're going to start looking at specific dinosaur adaptations and behaviors.
Starting with how and what dinosaurs ate.
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