How a Hot Planet Created the World’s Biggest Snake

How a Hot Planet Created the World’s Biggest Snake


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 by far was Titanoboa – the largest snake ever known. At 13 meters, it was about twice the size
of the biggest 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: What allowed a snake to grow to nearly twice the size of anything
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 called Cerrejon — 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 Cerrejon provided us with a
snapshot of a world that no longer exists – the earliest recorded neotropical rainforest,
dating to 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 that 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 of 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 boids
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 boids never get anywhere
near as big as Titanoboa. Based on the dimensions of its vertebrae,
as well as on the sizes of living boa species, experts estimate that it reached lengths just
under 13 meters. That’s as long as the largest T. rex! By comparison, the longest snake around today,
the reticulated python, is usually around 7 meters, with some outliers stretching out
as much as 9 meters. Based on its length, researchers have also
been able to estimate the mass of Titanoboa. And it likely tipped the scales at around
1135 kilograms, which is about as much 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 Cerrejon
formation revealed many more species of epic proportions. They unearthed a 6 meter long crocodile-like
reptile, called Acherontisuchus, and a turtle, Puentemys, that had a carapace some 1 and
a half meters across. So this left many experts wondering: how exactly
did these all of these creatures reach such monstrous sizes? Well, the first thing to note is that the
Cerrejon 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 open a niche for large predators. But probably the more important factor is
that all of these giant animals at Cerrejon 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 metabolism is just
how fast an organism burns calories, it actually includes all the chemical processes that keep
that 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. 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, Titanaboa 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 its jaws. It also had a lot of teeth compared to other
boids. And these traits have been observed today
in snakes that 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 it also means that it would be of no help
getting those mice out of my attic. The world’s biggest snake thrived for a
couple million years in the 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 global temperatures by 5 to 8
degrees C. 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’ve needed an average temperature around 30 or
31 celsius to maintain its massive size. In the end, we are 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 million years — the
blink of an eye in geologic time. Let it serve us as a reminder that even the
biggest creatures around are no match for a changing planet. Giant snake squeezes to this month’s Eontologists:
Patrick Seifert, Jake Hart, Jon Davison Ng, Sean Dennis, and Steve! Become an Eonite at patreon.com/eons and help
us keep bringing you the best stories from deep time! And thank you for joining me in the Konstantin
Haase Studio. Go to youtube.com/eons and subscribe! Thank you!

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