James Stewart

The fossil record suggested recovery, a sort of bounce-back period that would allow previously hunted species to thrive once again.

What it didn't suggest was dominance, and certainly not gigantism, and definitely not from snakes.

The saga of Titanoboa has more twists and turns than the coils of the snake itself, and it begins in an unlikely place, an open-pit coal mine in Colombia.

On the surface of it, Cerrejon is pretty unremarkable.

Lying in the lowland tropics north of the country, some 60 miles from the Caribbean coast, it's a forbidding, seemingly endless horizon of dusty nothingness, largely stripped of vegetation, a rare brown blot on the green map of Colombia.

In fact, this place is one of the world's largest coal operations, certainly the largest in South America, 700 kilometres squared, covering an area larger than the city of Chicago and employing some 10,000 workers.

But 60 million years ago, this area looked quite different.

It was a sweltering, swampy jungle, hotter and wetter than modern rainforests, dense with towering trees and teeming with colossal animals.

There is some irony in that all of that organic matter formed during the Paleocene epoch actually turned in to the coal that's now being mined.

Carlos Jaramillo, a paleontologist at the Smithsonian Tropical Research Institute, said that Cerrejon is the best and probably the only window on a complete ancient tropical ecosystem anywhere in the world.

So if you knew roughly where to look, there's a very slim chance you might find something more valuable than coal hiding in these mines.

The search for the monsters of the Paleocene epoch began in the 1990s, when Colombian geologist Henry García found an unfamiliar fossil.

He wasn't quite sure what he was looking at, so he placed the specimen in a glass display case in the coal company reception, where it was labeled petrified branch and forgotten about.

Now, flash forward nine years and a geology student named Fabini Herrera was hunting around in roughly the same spot when he noticed something unusual about the stones beneath his feet.

He reached down and picked up a piece of sandstone, turning it over in his hands.

On the other side of the stone, there was an impression of a fossil leaf etched into it.

He picked up another rock, and the same thing happened again, and then again, and again, and again.

He had stumbled upon a set of beautifully preserved fossil leaves, which he brought to the attention of Carlos Jaramillo, who we mentioned before.

Now if, like me, you're thinking what's so special about fossilised leaves, well, yeah, fair enough.

But they were about to reveal something far more intimidating, almost entirely by accident.