What Was Titanoboa? The Thirteen-Metre Snake of the Palaeocene
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In 2009 a team working the world's largest open-pit coal mine, at Cerrejon in northern Colombia, described vertebrae from a snake that had lived 58 million years ago, and the vertebrae were so large that the first person to see one thought it was a crocodile's. The animal they belonged to was about 13 metres long and weighed over a tonne, twice the length of the largest living snake, and it lived in a tropical swamp forest that was, on the evidence of the same snake, several degrees hotter than any rainforest today. Titanoboa is the largest snake known, and it is also a thermometer.
The find
Cerrejon is a coal mine that strips away a Palaeocene swamp, and the fossils come out of the shales between the seams: giant turtles, crocodiles, the earliest rainforest plants of South America, and, from 2004, vertebrae and ribs of a snake that were collected for years before anyone realised what they were. Jason Head and Jonathan Bloch, working with Carlos Jaramillo of the Smithsonian's tropical institute, identified them as a boid, a relative of the boas and anacondas, and named it Titanoboa cerrejonensis in 2009 from the remains of about thirty individuals. A skull, which snakes rarely leave since the bones are loosely joined and scatter, was found in 2012 and showed a head over 40 centimetres long with teeth suited to fish.
How big
A snake's length can be read from its vertebrae, since the bones scale with the body in a predictable way across living species, and the largest Titanoboa vertebrae are wider than any living snake's by a large margin. The estimate from the best-preserved specimens is a length of 12.8 metres and a mass of about 1,135 kilograms, with the widest part of the body about a metre across, roughly the height of a person's hip. The comparisons:
- •The reticulated python, the longest living snake, reaches about 7 metres and 150 kilograms
- •The green anaconda, the heaviest, reaches about 6 metres and 200 kilograms
- •Gigantophis, from the Eocene of Egypt and the previous record holder, was about 10 metres
- •Titanoboa: about 13 metres and over a tonne, longer than a London bus
How it lived
Titanoboa was a boid, and the boas and anacondas are constrictors that ambush prey in and near water, and the anaconda, the closest living analogue in habit, is what Titanoboa seems to have been at twice the scale: a swamp animal that spent most of its time in the water, where its weight was supported, and took prey at the edge. The skull, with its many closely spaced teeth and loose jaw, suggests a diet of fish, including the large lungfish found at Cerrejon, and the crocodiles and turtles of the same swamp, some of them two metres long, would have been within its range. A snake that size would have had few enemies and would have needed to eat rarely, as large constrictors do, going months between meals.
The thermometer
Snakes are cold-blooded, and the size a cold-blooded animal can reach depends on the temperature of its surroundings, since its metabolism runs on the heat it can absorb; the largest living snakes live in the hottest regions, and there is a relationship between the temperature of a place and the maximum size of the snakes in it. Working the relationship backwards, Head and his colleagues calculated that a snake of Titanoboa's size needed a mean annual temperature of 30 to 34 degrees, against 26 to 28 in the Amazon today, which made Cerrejon's Palaeocene forest the hottest tropical rainforest known. The estimate has been argued over, since large modern snakes may not be at the thermal limit, and the fossil leaves and soil chemistry from the same rocks give a slightly cooler figure of around 30, but the direction is agreed: the early Palaeocene was a greenhouse, with carbon dioxide several times today's level, and the tropics were hotter than they are now, not, as some models had predicted, capped by a thermostat.
Why it matters
Titanoboa lived about eight million years after the asteroid that ended the dinosaurs, in an ecosystem that had rebuilt itself around reptiles again, giant snakes, crocodiles and turtles filling the swamp while mammals were still small. It shows that the tropical rainforest, whose origin was once put in the Miocene, was already in place in South America in the Palaeocene with families of plants that are there now, and that a rainforest can exist at temperatures beyond the present, which bears on whether the tropics will die back or endure as the climate warms. The snake itself, reconstructed at full size, was displayed in Grand Central Station in New York in 2012, thirteen metres of it, to the alarm of commuters.
The takeaway
Titanoboa was a boid snake of about 13 metres and over a tonne that lived in the swamp forests of Colombia 58 million years ago, known from vertebrae, ribs and a rare skull found in the Cerrejon coal mine and described in 2009. It lived like a giant anaconda, ambushing fish and crocodiles in the water, and because a cold-blooded animal's size is set by temperature, it implies a Palaeocene rainforest several degrees hotter than any today, in a greenhouse world that had already regrown its tropical forest after the dinosaurs.