- [Matthew] Hello, and welcome
to the David H. Koch Hall of Fossils "Deep Time"
at the Smithsonian's National Museum of Natural History.
My name is Matthew Carrano,
and I'm the Curator of Dinosauria
here at the museum.
Since the first scientific recognition
of dinosaur fossils in the early 19th century,
these animals have captivated our attention.
How could the same planet that we call home
have produced such amazing creatures?
What was the world like when they were alive?
And how can we know these things
about species that lived so long ago?
The "Deep Time" exhibit explores all these questions
using the Museum's amazing fossil collections.
The first dinosaurs appeared in the Triassic period,
more than 230 million years ago.
They were small, two-legged,
land-living carnivores,
catching their prey with grasping hands and sharp teeth.
This Eoraptor is one of the earliest known dinosaurs
to have lived.
Early dinosaurs lived alongside many other reptile groups,
some of which were much more impressive in size,
as well as the earliest mammals.
Although most dinosaurs are long gone,
we do know quite a lot
about how they bred, grew,
what they ate, and how they moved.
We've been able to learn this
by studying their fossils,
as well as studying their living relatives,
birds and crocodilians.
Dinosaurs laid eggs,
and they laid them in nests
like that of the theropod Allosaurus
here in front of us.
Dinosaur nests have been found all over the world
from many different species.
We know that these parents
provided some level of care for their offspring,
just like birds and crocodilians do today.
Some nest sites have been found
that were buried so quickly
that the dinosaur parent was buried
right on top of the eggs.
Although, of course, only smaller species
probably actually sat on the eggs.
Others, though, may have guarded the nest from nearby
or kept them warm under piles of vegetation.
Dinosaurs would have grown rapidly
from their size in hatching.
Even the largest dinosaurs,
like Diplodocus at the top of this display,
would have started life
by emerging from an egg
no bigger than a football.
But after hatching, they grew very fast,
reaching their adult size
by about the age of 20.
Why so fast?
Well, the longer a young dinosaur stayed small,
the more vulnerable it was to being eaten.
Perhaps high rates of predation
led to populations where the young
had to mature very quickly.
The two dinosaurs in this display
are juvenile and teenage members
of the same species of Camptosaurus.
At first, paleontologists thought
that these were two entirely different species.
The little one they named Camptosaurus nanus,
meaning tiny Camptosaurus.
But later study revealed that both skeletons
were just different growth stages
of a species called Camptosaurus dispar.
We can tell how long these dinosaurs lived
and how fast they grew
by studying their bones.
Dinosaurs grew throughout their lives
and would lay down new layers of bone every year,
as you can see in this picture.
Scientists can cut out a section of the dinosaur bone
and count these layers,
like counting the rings of a tree.
The thicker the layer,
the faster the dinosaur was growing that year.
Typically they grew very quickly when they were young,
but much more slowly as adults.
Analyzing the microscopic anatomy of tissue in this way
is called histology.
In addition to knowing how dinosaurs grew,
we can tell what dinosaurs ate
by studying their bones and teeth.
Some dinosaurs were carnivores
and others were herbivores,
and much of their biology was influenced
by their respective needs to catch prey
or to avoid being dinner.
Here we can see a Stegosaurus
and a Ceratosaurus
locked in a battle for survival.
Their different adaptations as predator or prey
are visible in their anatomy.
Stegosaurus evolved a variety of defenses against predation.
The line of armored plates
running along its spine
was probably one defense against attack,
though they may also have been used
to show off to other Stegosaurus.
The spiked tail was also
a flexible and dangerous weapon.
Ceratosaurus has several traits
that allowed it to catch and to kill its prey.
The most obvious and frightening of these
are the sharp, serrated teeth,
combined with very large jaw muscles.
These made Ceratosaurus's mouth
a powerful offensive tool.
Ceratosaurus also may have used its strong foot claws
to help subdue prey.
Its short arms and hands, however,
were probably not that helpful.
Dinosaurs, like all animals,
evolved in concert with their environments.
The climate and ecosystems around them
influenced their biology
and helped shape the evolution of this group
of amazing reptiles,
whose fossils continue to fascinate us today.
Be sure to check out some of our other virtual tours
to see more of the "Deep Time" exhibit,
or head over to our YouTube page
for more video content with our other curators.