[♪ INTRO]
Wow, it’s amazing how small these are.
Squeaks and I have been learning about living things from a long time ago,
like the bacteria homes called stromatolites, and these trilobites here.
[Squeaks squeaks]
It’s true that lots of living things were really tiny long ago.
It took a long time for things like plants and animals to start
growing much bigger than this.
[Squeaks squeaks]
Oh, yeah!
Dinosaurs are a great example of really big animals from long ago.
Some dinosaurs had really huge bodies, with lots of cool, big body parts
like large teeth, and horns, and even frills.
There were some other big animals that lived even before dinosaurs did,
though, and they had some really interesting body parts, too.
Hey Squeaks! Would you like to use your time machine to visit one?
[Squeaks squeaks]
Okay, great!
Let’s set the time machine for 270 million years ago, and… go!
[Whooshing Time Travel Noises]
Welcome to the end of a time called the Permian Period.
We just went back 270 million years.
That’s before the oldest known dinosaur came around.
Are you ready to meet one big, ancient animal?
[Squeaks squeaks]
It’s called Dimetrodon.
Dimetrodon could grow longer than 3.5 meters, or nearly 12 feet long.
That’s almost as big as a car!
[Squeaks squeaks]
Oh, Dimetrodon did look a lot like dinosaurs.
But they were actually related to the mammals we know today!
Mammals are animals that are usually furry, and drink milk when they’re little.
Dogs, cats, monkeys, rats, and even people -- we’re all mammals!
While we don’t know if Dimetrodon were furry or drank milk, they have a
special shape in their skull that’s just like one shared by mammals today.
This tells us that they’re more closely related to other ancient mammals
than to dinosaurs.
Special body parts like skulls can tell us a lot about different animals.
[Squeaks squeaks]
Oh, you want to know what the sail on Dimetrodon’s back tells us?
Hmm...Let’s take a closer look.
What do you notice about it?
What do you think, Squeaks?
[Squeaks squeaks]
Oh, great observations!
The sail does remind me of a fish’s fins.
In nature, the way something looks, or what its structure is,
has to do with how it works, or what its function is.
Like how an elephant’s long, bendy trunk lets it drink water
or pick leaves from trees!
How do you think Dimetrodon used its big, fin-like sail?
[Squeaks squeaks]
Oh, that’s a good guess.
Looking at Dimetrodon’s legs, though, scientists think this animal spent more time
living on land than swimming in water, so I don’t know if the sail
would have helped it swim like a fish.
Actually, scientists are still learning about what Dimetrodon’s special sail
helped it to do.
One idea is that the sail helped Dimetrodon to warm up when they were cold.
Let's look at the structure of that sail again.
To me, it kind of looks like a leaf.
Leaves have big, flat structures to catch lots of sunlight and make food for the plant.
Maybe the Dimetrodon could use their sails when they were cold,
so that the big surface of the sail would catch the warm light from the sun.
[Squeaks squeaks]
Oh! It could work a little like a solar panel!
That big, flat structure of the sail could have caught a lot of sunlight.
So its function might have been to catch all that sun and help
the Dimetrodon get warm.
But other scientists think that the sails could have been used
to impress other Dimetrodon.
By having really big sails, Dimetrodon could show off how big and tough they were,
able to carry around heavy sails without being afraid of predators seeing them.
If a Dimetrodon looked really tough with a big sail, it might help them to
find a mate, another Dimetrodon to help them have baby Dimetrodons.
In that case, the structure of the sail is just to be really big!
And its function is for other Dimetrodon to see it.
[Squeaks squeaks]
Oh, it’s going to take some hard work before we know
if either idea is right, Squeaks.
Right now, scientists are studying whether boy and girl Dimetrodon
had the same size of sails, or different sizes.
Other scientists have been searching for new Dimetrodon skeletons,
so we can take more measurements of sails.
The more we learn about the structure of the sails, the better we can guess
what function they had.
And while scientists keep researching and learning about the sails,
we can be excited to learn more and more about what big Dimetrodon
and other ancient creatures looked like, and how they acted!
What do you think Dimetrodon’s sails were for?
How would you use a big sail structure on your back?
What other big ancient animals are you excited to learn about?
Remember, if you’d like to keep learning and exploring with me, Squeaks,
and all of our friends, make sure to hit the subscribe button.
And we’ll see you next time, here at the Fort.
[♪ OUTRO]