"'Titanic' boa fossils provide clues to past tropical climate."

A vertebra of a modern Anaconda (left) and (right) a vertebra from the Titanoboa.

This snake could have been 2500+ lbs. and as long as a city bus.

From Nature:

Researchers have found fossils of the biggest known snake in the world, a discovery that could shed light on the climate of the tropics in the past.

The scientists estimate the snake lived 58 to 60 million years ago and was around 13 metres long. The giant, found in northeastern Colombia, dwarfs modern pythons and anacondas which usually don't exceed 6-6.5 metres and are thought to be the largest living snakes.

Since snakes are poikilotherms that, unlike humans, need heat from their environment to power their metabolism, the researchers suggest that at the time the region would have had to be 30 to 34 degrees Celsius for the snake to have survived. Most large snakes alive today live in the South American and southeast Asian tropics, where the high temperatures allow them to grow to impressive sizes.

"We've taken the snake and turned it into a giant thermometer," says lead author and vertebrate palaeontologist Jason Head of the University of Toronto in Canada, who says he "just about screamed" when he first saw the size of the fossils....

Using models1 based on the largest modern-day snakes and their estimate of the Titanoboa's size, the team calculated how hot the tropics must have been 58 to 60 million years ago, a period known as the Palaeocene. The mean annual temperature would need to be at least 30-34 degrees Celsius to support the snake's metabolism, the researchers report in Nature2. This range matches previous estimates from Palaeocene climate models that assume high atmospheric carbon dioxide concentrations3.

The results support the idea that the temperature difference between the Palaeocene tropics and higher-latitude regions was as large as it is today, even though the higher latitudes were much warmer during that time. This counters the so-called 'thermostat' hypothesis, which predicts that tropical temperatures would stay fairly stable even as other parts of the world heated up.