Hey, evolution, why aren't giant pets a thing yet, huh?
If dinosaurs grew enough to fill a whole room, why can’t I have a big red dog the size
of a house?
Well, they would take room sized poops though.
Hey everyone, Lissette here for DNews.
Part of what captures our imagination about dinosaurs is just how huge some of them were.
The American Museum of Natural History has a cast of a titanosaur that’s so big it
doesn’t completely fit in the dinosaur wing.
The 37 meter (122 foot) long behemoth’s head has to poke out towards the elevators.
It’s got individual bones bigger than people.
The very name of the group of dinosaurs it belongs to has the word TITAN in it.
But when you start to consider the size of some of these extinct species, it can make
you a philoso-raptor.
“Why isn’t any land animal this huge today?”
you may wonder...
Well you’re not the only one.
Paleontologists have been debating the same question, and they’ve come up with a number
of different factors that could explain why some giant reptiles of yesteryear dwarf modern
land creatures.
It’s important to keep in mind that dinosaurs lived a long time ago.
No duh, right?
But what you may not realize is, before the dinosaurs were wiped out they were living
on a completely different kind of earth than we live in today.
Dinosaurs actually started coming onto the scene about 230 million years before present.
During their existence, CO2 levels were all over the place.
Estimates vary but (for some stretches) there could have been 3 to 5 times as much carbon
dioxide in the atmosphere as there is today.
This means the world, on the whole, was a lot hotter - even up at higher latitudes.
And, because at the beginning of the Mesozoic Era, all land was clumped together in Pangea,
the ocean didn’t have as much of a cooling effect on the supercontinent.
This would make the planet a more hospitable place for, I don’t know, giant cold-blooded
reptiles that wouldn’t have to waste energy maintaining body heat.
See... another reason to worry about global warming.
Get out of that SUV and onto a bike unless you want to see T-rexes in your sideview mirror.
It may comfort you to know that paleontologists aren’t all in agreement on the exactly how
much the atmosphere’s impacted dinosaur size.
It could have had no effect at all, and whether or not dinosaurs were all cold-blooded, is
even up for debate.
Their size could have also been driven by an abundance of food.
All that CO2 meant there was likely more vegetation.
If there’s plentiful vegetation, then large herbivores can thrive.
They’d actually benefit from being bigger because longer intestines would be better
at breaking down plant matter and extracting its nutrients.
Then... they could spend less time chewing, and more time stuffing green down their giant
gullets.
Also if the herbivores grew larger, then they were harder for predators to take down.
Until the predators got bigger.
Then the herbivores would get bigger.
Then the predators would get bigger.
You see where this is going.
But there is an upper limit to size, because of physical constraints -- like gravity.
Part of the reason whales can get so huge is because the ocean supports their weight.
On land, a similar sized animal would crush itself without some clever life hacks.
Huge dinosaurs like sauropods had lightweight bones compared to mammals because theirs were
hollow.
Dinosaurs also had another advantage over mammals, when it comes to living large: they
laid eggs.
If they had to give birth to live young, it would be much harder for them to have large
offspring quickly.
For instance, elephants have 22 month gestation periods…
they can't breed very quickly because live-birth is so resource intensive -- and it requires
a large birth canal.
Interestingly, these traits of hollow bones and egg-laying have come in handy in a very
different way today: they make it possible for the descendants of dinosaurs to fly.
That’s right, I’m talking ‘bout birds.
Look, WHY they were so big is still a matter of debate, and hopefully we'll find more research
out there… but at the moment they’re trying to put together a hundred-million-year-old
puzzle with a lot of missing pieces.
For more on huge salt water creatures that are alive today, Don’t miss new episodes
of River Monsters, every Thursday at 9/8c on Animal Planet!
Seriously, though, dinosaurs equal birds.
Here’s a video all about their gradual shift from ferocious predators to feathered peckers.
So are you glad giant reptiles no longer run amok, or would you want a pet raptor?
Maybe tie a bandana ‘round it’s neck, name her Clover.
She would be the best dino ever.
Yes she would.