Today, we are used to seeing feathered dinosaurs flying around and roosting in trees.
Today, we are used to seeing feathered dinosaurs flying around and roosting in trees.

But few discoveries have so completely transformed our picture of the extinct dinosaurs than
But few discoveries have so completely transformed our picture of the extinct dinosaurs than

the revelation that they had feathers, too.
the revelation that they had feathers, too.

Or at least, some of them did.
Or at least, some of them did.

Over the past 20 years, dinosaurs of all types and sizes have been found with some sort of
Over the past 20 years, dinosaurs of all types and sizes have been found with some sort of

fluff or even full-on plumage.
fluff or even full-on plumage.

But these fuzzy discoveries have raised a whole batch of new questions.
But these fuzzy discoveries have raised a whole batch of new questions.

Like, exactly what kinds of dinosaurs had feathers?
Like, exactly what kinds of dinosaurs had feathers?

And how do we know for sure?
And how do we know for sure?

And, considering that the likes of T. rex and Psittacosaurus couldn’t fly
And, considering that the likes of T. rex and Psittacosaurus couldn’t fly

then what were their feathers even for?
then what were their feathers even for?

Well, find a perch and get comfortable, because I’m here to tell you everything we know
Well, find a perch and get comfortable, because I’m here to tell you everything we know

about dinosaurs and feathers.
about dinosaurs and feathers.

It took us a long time to make the connection between dinosaurs and feathers -- and birds
It took us a long time to make the connection between dinosaurs and feathers -- and birds

in general.
in general.

In fact, the first fossil to give us an inkling that dinosaurs had feathers was actually one
In fact, the first fossil to give us an inkling that dinosaurs had feathers was actually one

of the earliest specimens ever found.
of the earliest specimens ever found.

It was Archaeopteryx, discovered in 1861, from the Solnhofen limestone in Germany, which
It was Archaeopteryx, discovered in 1861, from the Solnhofen limestone in Germany, which

dates back to the Jurassic Period.
dates back to the Jurassic Period.

Archaeopteryx means “first wing”, and even the 1800s, experts could immediately
Archaeopteryx means “first wing”, and even the 1800s, experts could immediately

identify it as an ancient bird.
identify it as an ancient bird.

After all, at the time, birds were the only animals we knew that had feathers, and this
After all, at the time, birds were the only animals we knew that had feathers, and this

thing definitely had them.
thing definitely had them.

But Archaeopteryx had some other features, too -- ones that were kinda strange for a
But Archaeopteryx had some other features, too -- ones that were kinda strange for a

bird, like a long, bony tail; fingers with claws; and tiny teeth -- things that you usually
bird, like a long, bony tail; fingers with claws; and tiny teeth -- things that you usually

see in reptiles.
see in reptiles.

Those clues suggested that birds must have sprung from the reptilian branch of the tree
Those clues suggested that birds must have sprung from the reptilian branch of the tree

of life.
of life.

But no one could agree on what that actually meant.
But no one could agree on what that actually meant.

It took decades of study and debate before paleontologists started to see that little
It took decades of study and debate before paleontologists started to see that little

Archaeopteryx looked an awful lot like a dinosaur.
Archaeopteryx looked an awful lot like a dinosaur.

And it wasn’t until 1996 -- 135 years after Archaeopteryx was first found -- that a lucky
And it wasn’t until 1996 -- 135 years after Archaeopteryx was first found -- that a lucky

break confirmed what they had begun to suspect.
break confirmed what they had begun to suspect.

A beautifully preserved, articulated skeleton of a chicken-sized dinosaur was found in China.
A beautifully preserved, articulated skeleton of a chicken-sized dinosaur was found in China.

And along the neck, back, and tail of this little dino was a line of fuzz.
And along the neck, back, and tail of this little dino was a line of fuzz.

Paleontologists named this revolutionary discovery Sinosauropteryx
Paleontologists named this revolutionary discovery Sinosauropteryx

It confirmed that at least some non-avian dinosaurs had feathers, and that the history
It confirmed that at least some non-avian dinosaurs had feathers, and that the history

of feathers went back way farther than anyone knew.
of feathers went back way farther than anyone knew.

As it turned out, Sinosauropteryx would be just the first of many finds that would show
As it turned out, Sinosauropteryx would be just the first of many finds that would show

us that dinosaurs were fluffier, fuzzier, and more ornate than we had ever expected.
us that dinosaurs were fluffier, fuzzier, and more ornate than we had ever expected.

The fossil record has turned out to be so generous!
The fossil record has turned out to be so generous!

In fact, the growing menagerie of feathered dinosaurs has offered experts a pretty good
In fact, the growing menagerie of feathered dinosaurs has offered experts a pretty good

outline of how feathers evolved.
outline of how feathers evolved.

Dinofluff - which experts technically call protofeathers - probably goes all the way
Dinofluff - which experts technically call protofeathers - probably goes all the way

back to the Triassic.
back to the Triassic.

But since dinosaurs in different times and places had a variety of protofeather types,
But since dinosaurs in different times and places had a variety of protofeather types,

paleontologists are able to piece together how feathers went from basic filament structures,
paleontologists are able to piece together how feathers went from basic filament structures,

to ones that allowed flight.
to ones that allowed flight.

For example, Yutyrannus, a tyrannosaur from China, had little wisps
For example, Yutyrannus, a tyrannosaur from China, had little wisps

that grew from follicles in its skin.
that grew from follicles in its skin.

It also represents the largest dinosaur currently known with evidence of dinofuzz.
It also represents the largest dinosaur currently known with evidence of dinofuzz.

But from those simple bits of fluff, protofeathers became more complex over time.
But from those simple bits of fluff, protofeathers became more complex over time.

Dinos like the small tyrannosaur Dilong and the tiny carnivore Juravenator
Dinos like the small tyrannosaur Dilong and the tiny carnivore Juravenator

had protofeathers with a central stalk that branched off near the top.
had protofeathers with a central stalk that branched off near the top.

And once protofeathers started branching, they were able to take on all kinds of new
And once protofeathers started branching, they were able to take on all kinds of new

shapes.
shapes.

The central part of the feather became a hardened structure called a rachis, with
The central part of the feather became a hardened structure called a rachis, with

lots of little barbs and barbules, creating the vanes of the feather.
lots of little barbs and barbules, creating the vanes of the feather.

Dinosaurs that are closely related to birds - like Microraptor and Archaeopteryx - had
Dinosaurs that are closely related to birds - like Microraptor and Archaeopteryx - had

feathers like these.
feathers like these.

And interestingly, the closer you get to the origin of birds in the dinosaur family tree,
And interestingly, the closer you get to the origin of birds in the dinosaur family tree,

the greater the variety of feathers you find on different parts of their bodies.
the greater the variety of feathers you find on different parts of their bodies.

So, to get a sense of how common feathers were among the non-avian dinos, let’s take
So, to get a sense of how common feathers were among the non-avian dinos, let’s take

a tour of that family tree.
a tour of that family tree.

We’ll start with this big group of two-legged saurischian dinos: the theropods.
We’ll start with this big group of two-legged saurischian dinos: the theropods.

They include everything from the crested carnivore Dilophosaurus to the
They include everything from the crested carnivore Dilophosaurus to the

parrot-like omnivore Oviraptor.
parrot-like omnivore Oviraptor.

Zoom in and you’ll find a smaller group of theropods called the coelurosaurs
Zoom in and you’ll find a smaller group of theropods called the coelurosaurs

Every single lineage in this group has some kind of evidence of a feathery body covering,
Every single lineage in this group has some kind of evidence of a feathery body covering,

whether it was fuzz or full-on feathers.
whether it was fuzz or full-on feathers.

And this is the group that includes birds, along with a whole variety of other theropods,
And this is the group that includes birds, along with a whole variety of other theropods,

like the Therizinosaurs with those enormous hand claws, and none other
like the Therizinosaurs with those enormous hand claws, and none other

than T. rex.
than T. rex.

But that’s not all.
But that’s not all.

All the way over on the other side of the dinosaur family tree, there’s another, broader
All the way over on the other side of the dinosaur family tree, there’s another, broader

group called the ornithischians.
group called the ornithischians.

They’re nowhere close to birds, in evolutionary terms, but they have feather-like body coverings,
They’re nowhere close to birds, in evolutionary terms, but they have feather-like body coverings,

too.
too.

Take Psittacosaurus, a small horned dinosaur that used to run around
Take Psittacosaurus, a small horned dinosaur that used to run around

China.
China.

It’s been found with preserved quill-like filaments growing from its tail.
It’s been found with preserved quill-like filaments growing from its tail.

Likewise, fossils of a Jurassic dinosaur from Russia, called Kulindadromeus,
Likewise, fossils of a Jurassic dinosaur from Russia, called Kulindadromeus,

show that it was nearly covered with feather-like structures, despite the fact that it, too,
show that it was nearly covered with feather-like structures, despite the fact that it, too,

was far from birds.
was far from birds.

Now, the fact that feathers and feather-like structures show up in these very different
Now, the fact that feathers and feather-like structures show up in these very different

groups of dinosaurs can mean one of two things.
groups of dinosaurs can mean one of two things.

Either protofeathers evolved more than once throughout dinosaurs’ history …
Either protofeathers evolved more than once throughout dinosaurs’ history …

...or they actually go all the way back to the last common ancestor of all dinosaurs,
...or they actually go all the way back to the last common ancestor of all dinosaurs,

and were retained in some groups but lost in others.
and were retained in some groups but lost in others.

So, we have some pretty good data about the presence of feathers within certain groups
So, we have some pretty good data about the presence of feathers within certain groups

of dinosaurs.
of dinosaurs.

And we can use that to make informed guesses about which particular species had feathers.
And we can use that to make informed guesses about which particular species had feathers.

For dinosaurs like Microraptor, there’s direct evidence of feathers right there in
For dinosaurs like Microraptor, there’s direct evidence of feathers right there in

the rock.
the rock.

No question about it.
No question about it.

But then there are dinosaurs that we don’t have direct evidence of feathers for, but
But then there are dinosaurs that we don’t have direct evidence of feathers for, but

we think they probably had them.
we think they probably had them.

This is called phylogenetic bracketing -- using the presence of traits across related species
This is called phylogenetic bracketing -- using the presence of traits across related species

to make an educated guess where those traits might occur.
to make an educated guess where those traits might occur.

For example, most mammal fossils aren’t found with hair, but we expect that they did
For example, most mammal fossils aren’t found with hair, but we expect that they did

have hair, because we know their relatives do.
have hair, because we know their relatives do.

The same goes for the likes of T. rex.
The same goes for the likes of T. rex.

Even though there’s no direct evidence of feathers on T. rex, there’s a good chance
Even though there’s no direct evidence of feathers on T. rex, there’s a good chance

the tyrant king was at least a little fluffy, because other tyrannosaurs have been found
the tyrant king was at least a little fluffy, because other tyrannosaurs have been found

with protofeathers.
with protofeathers.

Ditto for Triceratops.
Ditto for Triceratops.

Because its little relative Psittacosaurus had bristles, perhaps
Because its little relative Psittacosaurus had bristles, perhaps

larger horned dinosaurs did, too.
larger horned dinosaurs did, too.

And then there are dinosaurs that may or may not have had any protofeathers at all.
And then there are dinosaurs that may or may not have had any protofeathers at all.

Will we be shocked by the discovery of an Apatosaurus or Ankylosaurus with protofeathers
Will we be shocked by the discovery of an Apatosaurus or Ankylosaurus with protofeathers

someday?
someday?

It’s possible.
It’s possible.

But there’s no direct evidence of that just yet, and no one has found any fluff on any
But there’s no direct evidence of that just yet, and no one has found any fluff on any

members of those dinosaur groups.
members of those dinosaur groups.

So, this brings us to another question: Why? Why did dinosaurs develop feathers in the first
So, this brings us to another question: Why? Why did dinosaurs develop feathers in the first

place?
place?

Well, feathers are a great example of an exaptation.
Well, feathers are a great example of an exaptation.

That’s a trait that evolved for one reason, but later became modified to do something
That’s a trait that evolved for one reason, but later became modified to do something

else.
else.

For instance, remember Sinosauropteryx?
For instance, remember Sinosauropteryx?

It lived on the ground and couldn’t fly.
It lived on the ground and couldn’t fly.

But its simple coat of fluff still had advantages.
But its simple coat of fluff still had advantages.

For one thing, feathers are great for insulation.
For one thing, feathers are great for insulation.

Think of that the next time you put on a down jacket.
Think of that the next time you put on a down jacket.

And they’re also really handy for display.
And they’re also really handy for display.

The tail of Sinosauropteryx was banded rust red and white, which probably
The tail of Sinosauropteryx was banded rust red and white, which probably

helped it signal to other members of its species.
helped it signal to other members of its species.

And other dinosaur displays were even more ornate!
And other dinosaur displays were even more ornate!

The fossilized remains of a small, strange dinosaur called Epidexipteryx
The fossilized remains of a small, strange dinosaur called Epidexipteryx

show it had long, ribbon-like tail feathers - structures that may have been well-suited
show it had long, ribbon-like tail feathers - structures that may have been well-suited

for doing the dinosaur version of a fan dance.
for doing the dinosaur version of a fan dance.

But even as protofeathers started to get more complex, and came to look more like the structures
But even as protofeathers started to get more complex, and came to look more like the structures

on the wings of birds, they still had plenty of uses for life on the ground.
on the wings of birds, they still had plenty of uses for life on the ground.

For example, an amazing skeleton of the dinosaur Citipati was found in Mongolia,
For example, an amazing skeleton of the dinosaur Citipati was found in Mongolia,

with its arms in a brooding position over a nest.
with its arms in a brooding position over a nest.

Based on what we know about its relatives, this dinosaur must have been feathered and
Based on what we know about its relatives, this dinosaur must have been feathered and

may have used its feather-covered arms to protect its nest.
may have used its feather-covered arms to protect its nest.

Feathered arms are also good for more active pursuits.
Feathered arms are also good for more active pursuits.

Studies of living birds, like chukar partridges, have shown that birds can get a better grip
Studies of living birds, like chukar partridges, have shown that birds can get a better grip

on inclined surfaces, like tree trunks and rocks, when they flap their wings as they
on inclined surfaces, like tree trunks and rocks, when they flap their wings as they

run.
run.

Smaller feathered theropods with long feathers on their arms, may have used this technique,
Smaller feathered theropods with long feathers on their arms, may have used this technique,

possibly to evade larger non-climbing predators.
possibly to evade larger non-climbing predators.

And finally, feathers might have made some dinosaurs even better hunters.
And finally, feathers might have made some dinosaurs even better hunters.

Ground-dwelling dinosaurs with long arm feathers like Deinonychus probably weren’t eviscerating
Ground-dwelling dinosaurs with long arm feathers like Deinonychus probably weren’t eviscerating

their prey with those terrible foot claws.
their prey with those terrible foot claws.

Instead, they may have acted like modern day raptors - pinning down small prey and flapping
Instead, they may have acted like modern day raptors - pinning down small prey and flapping

their wings to help stabilize their grip.
their wings to help stabilize their grip.

So, feathers had all sorts of uses.
So, feathers had all sorts of uses.

That’s what made them the ultimate dinosaur accessory.
That’s what made them the ultimate dinosaur accessory.

And it’s what allowed some dinosaurs to eventually take to the air.
And it’s what allowed some dinosaurs to eventually take to the air.

What evolved on the ground opened ways for the terrible lizards to take flight, a tradition
What evolved on the ground opened ways for the terrible lizards to take flight, a tradition

they have mostly kept to this day.
they have mostly kept to this day.

But our knowledge of the when, why and how of dinosaur feathers is still pretty new.
But our knowledge of the when, why and how of dinosaur feathers is still pretty new.

Remember, it took nearly a century after the discovery of Archaeopteryx for paleontologists
Remember, it took nearly a century after the discovery of Archaeopteryx for paleontologists

to finally see the relationship between birds and dinosaurs.
to finally see the relationship between birds and dinosaurs.

And it took another three decades before fossils like Sinosauropteryx started changing our
And it took another three decades before fossils like Sinosauropteryx started changing our

view of how feathery some dinosaurs really were.
view of how feathery some dinosaurs really were.

Each new find will continue to enhance our vision of the non-avian dinosaurs.
Each new find will continue to enhance our vision of the non-avian dinosaurs.

But for now, the next time that you see a winged dinosaur flying around, feasting at
But for now, the next time that you see a winged dinosaur flying around, feasting at

your bird feeder, or standing on the head of some statue, take a moment to appreciate
your bird feeder, or standing on the head of some statue, take a moment to appreciate

the hundreds of millions of years of evolution that made that sight possible.
the hundreds of millions of years of evolution that made that sight possible.

Thanks for joining me for this extra-feathery episode of PBS Eons!
Thanks for joining me for this extra-feathery episode of PBS Eons!

Now, what do you want to know about the story of life on Earth?
Now, what do you want to know about the story of life on Earth?

Let us know in the comments.
Let us know in the comments.

And don’t forget to go to youtube.com/eons and subscribe!
And don’t forget to go to youtube.com/eons and subscribe!

And you’re not done exploring yet are you?!
And you’re not done exploring yet are you?!

Check out some of our sister channels from PBS Digital Studios!
Check out some of our sister channels from PBS Digital Studios!

If you’re interested in great beginnings like we are, then check out the new channel,
If you’re interested in great beginnings like we are, then check out the new channel,

Origin of Everything, which explores history of objects and ideas from everyday life -- from
Origin of Everything, which explores history of objects and ideas from everyday life -- from

where the hashtag came from to why 18 year olds are considered adults.
where the hashtag came from to why 18 year olds are considered adults.