Fossils of Largest Snake Give Hint of Hot Earth
New York Times
2009-02-05
Some 60 million years ago, well after the demise of the dinosaurs, a giant relative of today’s boa constrictors, weighing more than a ton and measuring 42 feet long, hunted crocodiles in rain-washed tropical forests in northern South America, according to a new fossil discovery.
The fossil find — a batch of super-sized vertebrae pulled from an open-pit coal mine in northeast Colombia — is remarkable enough just as a paleontological extreme. The species, given the name Titanoboa cerrejonensis, is now the largest known snake species ever discovered.
But the existence of such a large snake may also help clarify how hot the tropics became during an era when the planet, as a whole, was far warmer than it is now, and also how well moist tropical ecosystems can tolerate a much warmer global climate.
That last question is important in assessments of how human-driven global warming might affect the tropics. Some scientists foresee the Amazon’s drying up, for instance, although other work cuts against that conclusion.
The discovery and its climatic implications are described in Thursday’s edition of the journal Nature.
An independent critique of the work by Matthew Huber, an earth and climate scientist at Purdue, also published in Nature, said the findings provided a hint that the tropics could get a lot warmer than they are now, but also “attest to the resiliency of tropical ecosystems in the face of extreme warming.”
With scant precise evidence of past temperature changes on land in the tropics, there is still substantial debate about whether these regions have gotten much warmer than typical steamy tropical conditions today — with an annual average temperature of 75 to 79 degrees Fahrenheit.
The team examined how warm it had to be for a snake species to be that large by considering conditions favoring the largest living similar tropical snake, the green anaconda, said Jason J. Head, the lead author of the paper and a paleontologist at the University of Toronto. They concluded that Titanoboa could have thrived only if temperatures ranged from 86 to 93 degrees.
Fonte
http://www.nytimes.com/2009/02/05/science/...ke.html?_r=1&em
