Titanoboa

Largest serpent lived in earliest known Neotropical rainforest

Biology News

Titanoboa cerrejonensis Credit: Courtesy of Indiana University

Plant macrofossils from Cerrejón side-by-side with similar leaves from living neotropical plants

Scientists examining the remains of the huge snake

Titanoboa, the biggest snake on record, lived in this forest 58 million years ago. This huge serpent was 13 meters (42 feet) long with a weight of 1140 kilograms (2510 pounds) — estimates based on the size and length of its vertebral column.

"At its greatest width, the snake would have come up to about your hips," said Indiana University Bloomington geologist David Polly, who analyzed the monster snake fossil. "The size is pretty amazing."

Modern neotropical rainforests, with their palms and spectacular flowering-plant diversity, seem to have come into existence in the Paleocene epoch, shortly after the extinction of the dinosaurs 65 million years ago,^†

Pollen evidence tells us that forests before the mass extinction were quite different from our fossil rainforest at Cerrejón. We find new plant families, large, smooth-margined leaves and a three-tiered structure of forest floor, understory shrubs and high canopy.

Historically, good rock exposures and concentrated efforts by paleontologists to understand the evolution of neotropical rainforests have been lacking. "The Cerrejón mining operation is the first clear window we have to see back in time to the Paleocene, when the neotropical rainforest was first developing," said Scott Wing, a paleontologist from the Smithsonian's National Museum of Natural History.

Some of the more than 2,000 fossil leaves, including the compound leaves and pods of plants in the bean family (Fabaceae) and leaves of the hibiscus family (Malvaceae) are among the oldest, reliable evidence of these groups. This was the first time that the plant families Araceae, Arecaceae, Fabaceae, Lauraceae, Malvaceae and Menispermaceae -- which are still among the most common neotropical rainforest families -- all occurred together.

Many newcomers to modern rainforests remark that the leaves all look the same, a reasonable observation given that most have smooth margins and long "drip-tips" thought to prevent water from accumulating on the leaf surface.

S. Joseph Wright, a scientist at the Smithsonian Tropical Research Institute, has noted that all of the areas in the world today with average yearly temperatures greater than 28 C are too dry to support tropical rainforests. If tropical temperatures increase by 3 C by the end of this century as predicted in the 2007 report of the Intergovernmental Panel on Climate Change, "We're going to have a novel climate where it is very hot and very wet. How tropical forest species will respond to this novel climate, we don't know," said Wright.

Based on leaf shape and the size of the cold-blooded Titanoboa, Cerrejón rainforest existed at temperatures up to 30-32 C and rainfall averages exceeded 2500 mm per year.

But Titanoboa's rainforest was not as diverse as modern rainforests. Comparison of the diversity of this fossil flora to modern Amazon forest diversity and to the diversity of pollen from other Paleocene rainforests revealed that there is a smaller variety of organisms at Cerrejón than one would expect.

"We were very surprised by the low plant diversity of this rainforest. Either we are looking at a new type of plant community that still hadn't had time to diversify, or this forest was still recovering from the events that caused the mass extinction 65 million years ago," said Wing. "Our next steps are to collect and analyze more sites of the same age from elsewhere in Colombia to see if the patterns at Cerrejón hold, and study additional sites that bracket the Cretaceous mass extinction,^† in order to really understand how the phenomenal interactions that typify modern rainforests came to be."