MAN: About 59 million years ago, the rainforest of Colombia was full of giants.

It wasn't long after the extinction that ended the reign of the non-avian dinosaurs, and the fauna in this part of South America were already starting to get big again.

In this lush swampy ecosystem, there were huge turtles, way bigger than the largest members of their group today.

And there were specialized fish-eaters with long, narrow snouts, crocodile relatives that were every bit as long as today's biggest saltwater crocs.

But the largest animal lurking in that ancient forest, like, by far, was titanoboa, the largest snake ever known.

At 13 meters, it was about twice the size of the bigger snakes alive today.

It was like seven of me-long.

And "me" has a lot of questions about this thing, like why can't I have one anymore?

Because it sounds really cool and I got mice in my attic.

But also, where did it come from?

Is it related to any living snake species, and how did it live?

What did it eat?

How does a snake that big actually work?

But the biggest question for me has just been about its bigness-- like, what allowed this snake to grow to nearly twice the size of any snake we know today?

Well, it seems titanoboa was truly a product of its environment, specifically of the climate that it lived in.

It's only been in the past few years that we've put together the many pieces of this puzzling creature, but it turns out that the greatest snake that the world ever saw was made possible by a warming planet.

The story of titanoboa's discovery begins in the early 2000s, when a geology student on a field trip found several fossil leaves at a site Cerrejón, a large coal mine in Colombia near the border with Venezuela.

And those fossil leaves were so fascinating that they attracted researchers who ended up leading a series of expeditions that lasted more than a decade.

On those digs, scientists found a treasure trove of plant fossils, including things like early beans, bananas, and chocolate plants-- relatives of the plants that still live in South America today.

The fossils of Cerrejón provided us with a snapshot of a world that no longer exists-- the earliest recorded neo-tropical rainforest dating back 58 million to 60 million years ago.

And during one of these expeditions, another kind of fossil was found that raised a lot of questions-- not from a plant, but an animal.

It was a strange-looking vertebra, one that resembled the same bone from an anaconda, but way bigger.

This single bone would turn out to be the first evidence of a truly massive snake.

In time, researchers would collect over 100 fossil remains of ribs, vertebrae, and even parts of the skull representing 28 individual snakes of this species.

And those vertebrae can tell you a lot about a snake because if snakes have anything, it's a lot of backbone.

And scientists could tell from the pattern of features on these vertebrae, like the position of certain holes and ridges that it belonged to a member of the family known as boidae, which includes all of the boas.

Now there aren't many fossils of boas older than titanoboa, which is about 59 million years old.

But based on what we know about their evolutionary relationships with other reptiles, we think that snakes evolved from a four-limbed ancestor sometime before the middle Jurassic period 167 million years ago.

But some of the earliest fossils that we'd call snakes based on their skulls probably still had limbs, so figuring out what counts as an early snake is complicated.

And in fact, living boas, as well as pythons, actually have vestigial hind limbs called spurs-- evolutionary relics of this tetrapod ancestor.

We don't know if titanoboa had spurs, but given that all of its living relatives do, it's possible.

But still, living boas it's never get anywhere near as big as titanoboa.

Based on the dimensions of its vertebrae, as well as on the sizes of living both species, experts estimate that it reached lengths just under 13 meters.

That's as long as the largest T-Rex.

Now by comparison, the longest snake around today, the reticulated python, is usually around seven meters, with some outliers stretching out as much as nine meters.

Based on its length, researchers have also been able to estimate the mass of titanoboa, and it likely tipped the scales at around 1,135 kilograms, which is about the same as a bull bison, or an adult male giraffe, so not exactly a lightweight.

Titanoboa was not just the largest snake species ever known.

It was also the largest non-marine vertebrate in its day.

But this giant reptile was not alone in that Colombian rainforest.

As paleontologists later discovered, the Cerrejón formation revealed many more species of epic proportions.

They unearthed a six-meter-long crocodile-like reptile called acherontisuchus, and a turtle, puentemys, that had a carapace some 1 and 1/2 meters across.

So this left many experts wondering, how exactly did all these creatures reach such monstrous sizes?

Well, the first thing to note is that the Cerrejón formation dates back to just a few million years after the Cretaceous- Paleogene extinction event that wiped out all of the non-avian dinosaurs and many other megafauna, and that left an open niche for large predators.

But probably the more important factor is that all of these giant animals at Cerrejón were reptiles, and most reptiles, of course, are cold-blooded, so their body temperatures vary depending on the ambient temperature of their environment.

As a result, their metabolisms change with the temperature too.

They speed up when temps are higher and slow down in colder environments.

That means that temperature has a huge effect on cold-blooded reptiles.

So while you might think that metabolism is just how fast an organism burns calories, it actually includes all of the chemical processes that keep an organism alive.

And for a reptile, when it's warmer, all those chemical reactions are going faster, so it can do things like grow faster, assuming it's got enough food.

So even though bigger animals typically have slower metabolisms, this effect of high temps on reptiles is so strong that it can allow a creature like titanoboa to reach its terrific proportions.

Now how hot of a climate did this snake live in, exactly?

Well, the temperatures of long-gone ecosystems can be estimated using fossils of reptiles like titanoboa based on what we know about the relationship between temperature and body size in modern cold-blooded animals.

This method shows that titanoboa would have needed an average temperature of about 30 to 34 degrees Celsius to survive.

Now some researchers argue that this would have been so hot that the snake would actually have overheated.

But other methods have been used to study the ancient climate, like analyzing marine core samples and the ratios of carbon isotopes in fossil leaves.

And these methods show that the temperature was above 25 degrees Celsius, and maybe as high as 31 degrees.

So either way, it was warmer then than in today's average rainforest.

And in a lush environment with such steamy temperatures, titanoboa had plenty of dining options.

But when paleontologists studied the skull morphology of this giant snake, they were a little surprised by what they learned about its diet.

In most snakes, the teeth are firmly fused to the jaws by a bone-like tissue.

But titanoboa's teeth were only weakly attached to his jaws.

It also had a lot of teeth compared to other boas.

And these traits have been observed today in snakes specialize in eating fish, like the brown water snake and the banded sea krait.

These features suggest that titanoboa was the first known fish-eating boa, living or extinct.

And I guess it also means it would be of no help getting those mice out of my attic.

The world's biggest snake thrived for a couple of million years in the late Paleocene epoch, its giant lifestyle made possible by the extreme climate at the time.

But as with all things, it was not meant to last.

Titanoboa lived just a few million years before global temperatures spiked even higher in an event known as the Paleocene-Eocene Thermal Maximum, which we've talked about before.

Around 56 million years ago, the atmosphere contained massive amounts of carbon dioxide that raised the global temperatures by 5 to 8 degrees Celsius.

And this period of global warming lasted for about 200,000 years.

But after that, things cooled back down-- a lot.

Around 49 million years ago, the climate began to cool, eventually leading to the formation of the Antarctic ice sheet.

And while we don't know exactly why or when titanoboa went extinct, it probably would have needed an average temperature of 30 or 31 degrees Celsius to maintain its massive size.

In the end, we're all products of our environments, shaped by the worlds we live in.

In the case of titanoboa, a freakishly hot climate created an environment that fostered the biggest snake that ever lived, but only for a couple of million years-- the blink of an eye in geologic time.

So let it serve as a reminder that even the biggest creatures around are no match for a changing planet.

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