Every time I make a video about an extinct fossil creature I’m reminded there’s a
lot of confusion out there about what is and isn’t a dinosaur.
And you’d be forgiven for being kinda confused.
I mean, why is this a dinosaur, but this isn’t.
And this is, but this isn’t?
What about this?
Dinosaur?
No.
But this is?
Maybe paleontologists are just messing with us.
Or… maybe the question of what is and isn’t a dinosaur goes deeper than we think?
Well, like an intrepid fossil hunter, I set out to dig up an answer, and what I found
teaches us a lesson about how hard it is to build a picture of the past when you only
have a few puzzle pieces, and a lot about why we classify things the way we do.
Hey smart people, Joe here.
You might be surprised to learn just how many different types of -saurs there are
There are lots of different groups, mostly of reptiles, that have “saur” in their
name.
Oh yeah, that’s paleontologist Steve Brusatte
I study dinosaurs and all sorts of other fossils, but mostly dinosaurs.
And I wrote the book “The Rise and Fall of Dinosaurs” a couple of years ago.
There’s pterosaurs (those are the pterodactlys), plesiosaurs, There are mosasaurs and pliosaurs,
and ichthyosaurs there’s even groups like lepidosaurs, these are still around today.
That’s just a very common root-word, it basically means lizard.
(I think it’s greek)
It is Greek [look down], I checked.
And we can’t forget everyone’s favorite not-a-dinosaur, Dimetrodon, which actually
predates the dinosaurs and is more closely related to us mammals than T. rex or any of
the other “saurs”.
And Basilosaurus?
That thing’s an early whale!
Clearly, there’s a tendency to call any extinct, scaly thing with teeth a dinosaur,
even when they’re not.
But to figure out what dinosaurs are, we need to go back to when they were invented.
Ok, I mean the ancient reptiles we call “dinosaurs” evolved… more than 200 million years ago,
but the word “dinosaur”?
That arrived around 1841…
…thanks to Sir Richard Owen, who is giving me some strong Argus Filch vibes.
Guys like Owen had made careers out of naming and organizing all the animals and bones the
very friendly and not at all problematic British Empire was bringing to their doorstep from
across the globe.
One strange bone had been pulled from a quarry in England in the 17th century, which, thanks
to its odd shape was originally misidentified as the thigh of a Roman War Elephant, and
later misidentified again as… oh… heh… oh my!
Well, I’m not saying that.
Some very posh gentleman scientists of England eventually realized this and other bones came
from an extinct reptile, and they named it Megalosaurus, meaning “great lizard”.
Very original, guys.
When Argus…
I mean Richard Owen studied these and the bones of another reptile named Iguanodon,
he decided they had enough traits in common to be their own group, and…
…it was Richard Owen, who came up with that name, “Dinosauria,” the terrible lizards.
…And then from that point on people found more and more of these giant, ancient things
in rocks all over the world.
And people started to name new species, and they started to classify things as “dinosaurs”.
People from indigenous and other cultures around the world had been uncovering evidence
of these weird extinct creatures for a long time.
Like this Native American art in Utah inspired by footprints in the surrounding rock.
Posh gentleman scientists didn’t “discover” these creatures, but they gave them “official”
scientific names and began building a system to organize them.
And one of those posh gentleman scientists influenced the way we think about and organize
living things more than any other: The Smeagol of the HMS Beagle, the acorn that planted
the tree of life… my boy Chuck Darwin.
Before Darwin, there were ways of putting living things into categories.
Remember this?
But Darwin’s world-changing idea was that things that are closely related also share
ancestry, and if you follow the trail of common ancestors back far enough, everything comes
down to one great common ancestor of life.
After Darwin, people didn’t just sort things into different buckets based on certain traits
or features, they organized them based on a system of shared ancestry, and how those
traits or features change over time.
It was kind of a big deal.
So when we take Richard Owen’s original definition of “dinosaur”, and apply Darwin’s
new way of looking at how things are related, we get something close to our modern definition
of dinosaurs:
Iguanodon, megalosaurus… so you take them, you go down to their common ancestor, and
anything that falls within that part of the tree is a dinosaur…
Now the shape of this tree has changed and will continue to change over time as scientists
find new dinosaurs with new traits that are related in new ways.
But the tree always stays rooted in that common ancestor.
So how do we decide if something goes on the tree?
There are a few general rules.
Swimming things, not dinosuars.
Flying things, also not.
And if the thing runs around like this, chances are it's not a dino either.
But to really map out those branches, scientists use long lists of traits and characteristics,
enough to fill textbooks, that they can measure and plug into computer algorithms and figure
out not only if a new fossil belongs in the dinosaur group, even what sub-branch and sub-SUB-branch
they belong to on the tangled tree that grew from that common ancestor.
We don’t even know for sure what that common ancestor was, and it wouldn’t have been
too different from its closest relatives that aren’t dinosaurs.
But everything that descended from that thing is a dinosaur, because that’s what we say
a dinosaur is.
And this is where it gets kind of weird.
Because there’s nothing in nature that says a dinosaur has to be this.
It’s just a convention.
An agreement.
The same way a baseball game only works because everyone agrees to play by the same rules.
I mean, think of borders on a map: The boundary separating northern Illinois from Indiana
is a made up thing.
It’s only a line with cornfields on both sides.
Nothing in nature that says the boundary has to be here.
It could be here, or here.
But because a group of people agreed to put it here, and everyone agrees that the boundary
is here, it’s a useful made up thing.
It lets us group things together, it lets us separate things, and it lets us organize
things inside those boundaries.
And just like a state or national boundary, the definition of a dinosaur is something
we made up.
Definitions for pterosaurs, plesiosaurs, and all the other saurs and not-a-saurs?
We made those up too.
But even though they’re made up, they’re useful.
And even though the details of the definitions can change over time, everyone agrees to change
with them.
And that is what lets science happen.
So a dinosaur is a pigeon, and a triceratops, and all the descendants of their most common
ancestor, thanks to a guy named Richard Owen, a dude named Charles Darwin, and that thing.
But…
You can easily imagine a world, where in the victorian times in England, some other well-connected,
wealthy posh high-society person discovered a beautiful skeleton of say a pterodactyl,
you could see how Richard Owen, when he made his definition of a dinosaur, he might have
included the pterodactyls in that definition.
Then the convention would have been different, and eventually, the definition we would have
put on the family tree would have included pterodactyls.
It’s easy to see how little changes in the history of how we discover and study things,
have big effects on how we later classify and define things.
So maybe somewhere in the multiverse, there’s a world where pterodactyls are dinosaurs.
And even if the science they do there is a little different from ours, as long as everyone
agrees, it’s just as valid as the science we do here in this universe.
Except for this guy [Dimetrodon].
I don’t care what universe you’re in, still not a dinosaur.
That's just wrong
Stay Curious