Fossilized remains of a boa constrictor cousin that stretched 13 meters long and tipped the scales at more than a ton represent the largest snake ever found. The creature, dubbed Titanoboa cerrejonensis, lived some 60 million years ago in a neotropical rain forest in what is now northeastern Colombia. Identified on the basis of vertebrae recovered from an open-pit coal mine, Titanoboa is believed to have dined on crocodiles, among other creatures.

In addition to expanding the known limits of snake biology, the ancient serpent contains clues to primeval rain forest climate. Because snakes and other reptiles are "cold-blooded," or poikilothermic, their body temperature and hence their life processes is dependent on that of the surrounding air. The warmer the air is, the larger they can grow.

Scientists calculate that to attain its behemoth body size (which bests that of the modern-day record holder, a reticulated python, by nearly three meters), Titanoboa would have to have inhabited an environment with a mean annual temperature of at least 30 to 34 degrees Celsius (86 to 93 degrees Fahrenheit) significantly toastier than today's typical tropical forecast of 24 to 26 degrees C.

Some climate models predict that equatorial locales have been relatively sheltered from the effects of the planet's natural "greenhouse" phases, but the evidence from Titanoboa indicates that during these events, places that were already hot actually got hotter. In fact, shortly after Titanoboa's reign, tropical temperature may have risen so much as to cause widespread heat-related death, although the researchers have not yet found empirical evidence of the effects of such a scorching episode. The findings were published in the February 5 Nature.