Ancient tropical giant telling of past temperatures

The largest species of snake ever found, Titanoboa cerrejonensis, is described in Nature this week. The discovery of this relative of the Boa constrictor has implications not only for our understanding of the evolution giant snakes and their relationship to past climate, but also for the evolution of global climate.

Based on the discovery of fossil vertebrae, aged between 58 million and 60 million years old, from the oldest known neotropical rainforest fauna from the Cerrejón Formation in northeastern Colombia, Jason Head from the University of Toronto, Canada, and colleagues estimate the body length of T. cerrejonensis at 13 m and its mass at 1,135 kg.

The authors suggest that a cold-blooded snake of this size would require a minimum mean annual temperature of 30–34 °C to survive — which is hotter than today’s tropics. The finding calls into question the idea that the climate system has a ‘thermostat’ that regulates tropical temperatures.

Commenting in a related ‘News & Views’ article, Matthew Huber from the Purdue Climate Change Research Center, USA, raises several questions stemming from the work and notes that more work is necessary. “For the moment, however,” he concludes, “the burden of proof is on those who argue that the tropics do not warm substantially in a greenhouse world.”