
This drawer holds just
some of the hundreds of
the Cretaceous fossils from the
Washington D.C. area
here in the National Museum of
Natural History collections,
and it provides a really
great example of
one of the common problems
that paleontologists face.
That is most of the fossils
we find are isolated.
We get individual bones or
teeth and the challenge is
to identify them.
It's a really simple
process of observation and
comparison that ultimately
allows us to figure out both
what part of the animal we
have and how many animals
together we
have represented.
Here's a tooth. Here's a claw,
so a bone that has a
somewhat tooth-like shape.
They're both curved,
they're both pointed,
but we can still
tell them apart.
The tooth has an enamel covering
so it's relatively shiny.
This is a meat-eating
dinosaur tooth,
which means it
has sharp edges,
and they are serrated
like a steak knife.
In contrast, the claw,
because it is made of bone
has a somewhat
spongy texture.
And it has these
grooves on the sides,
it would have been
covered in a sheath,
which would have been
made of keratin like
your fingernails.
It's got a flat bottom and
an area here where it would
have touched the
finger it was attached to.
So even though they are
very generally similar,
the basic shapes,
we can look at the
details and figure out
these are two
different fossils.
Here in the
Washington D.C. area,
we find teeth as the
most common dinosaur
fossils.
And these are four examples,
four different kinds
of dinosaurs,
and you can see how the
shapes are really quite
different from
one to the next.
We can look at them and make
comparisons to figure out
which kinds of
dinosaurs these are.
These two fossil teeth
represent two different
meat-eating dinosaurs.
They are obviously
quite different in shape,
but there are also many
other features about them
that allow us to
distinguish them.
For example, under the
microscope, we can look at
the serrations on the
edges of these teeth.
They are, themselves,
very differently shaped,
the teeth have
different proportions
and different curvatures.
So it is unlikely that these
come from simply older and
younger individuals or
bigger and smaller ones,
more likely they are
from different species.
We also have several species
of plant-eating dinosaurs.
These two teeth come
from two different species.
This is from an armored
dinosaur called a nodosaur,
and it has a triangular
tooth with these very large
points on it, which would
have been quite useful for
chomping plant material.
This tooth is from a
sauropod dinosaur called
Pleurocoelus and it would
have a mouthful of these
very blunt teeth for
stripping leaves off of
tress and other
larger plants.
We can tell that they are
not meat-eating dinosaurs
from the shapes overall and
we can tell of course that
they are two different
species because the teeth
themselves are very
different from one another.
Some people believe that
is possible to identify the
actual species of dinosaur
from this particular tooth;
however, we know that
different species of
dromaeosaur have
very similar teeth.
Without having more
fossils of the animal,
its really not possible to
be specific about the kind
of dromaeosaur we have.
Even though we don't get
complete dinosaur skeletons
here in Washington D.C.,
a collection like this
is really important,
by making these kinds of
observations and comparisons
we can tell we have almost a
dozen species of dinosaurs
ranging from the size of a
chicken to almost the size
of a house.
That is actually really
important to understand what
life was like here
110 million years ago.
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