Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

• Published in: Nature 2009-02, Vol.457 (7230), p.715-717
• Main Authors: Hastings, Alexander K, Herrera, Fabiany A, Polly, P. David, Bloch, Jonathan I, Cadena, Edwin A, Jaramillo, Carlos A, Head, Jason J, Bourque, Jason R
• Format: Article
• Language: English
• Subjects: Animals; Atmosphere - chemistry; Biological Evolution; Body Size; Body temperature; Body Temperature Regulation; Boidae - anatomy & histology; Boidae - metabolism; Carbon dioxide; Carbon Dioxide - analysis; Cenozoic; Climate models; Coastal plains; Colombia; Earth sciences; Earth, ocean, space; Energy Metabolism; Environmental aspects; Equator; Estimates; Etymology; Evolution; Exact sciences and technology; Fossils; High temperature; History, Ancient; Humanities and Social Sciences; Language and languages; letter; multidisciplinary; Paleocene; Paleontology; Physiological aspects; Rainforests; Science; Science (multidisciplinary); Snakes; Temperature; Temperature gradients; Terrestrial ecosystems; Tropical Climate; Tropical environments; Vertebrate paleontology
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature07671

The largest extant snakes live in the tropics of South America and southeast Asia where high temperatures facilitate the evolution of large body sizes among air-breathing animals whose body temperatures are dependant on ambient environmental temperatures (poikilothermy). Very little is known about ancient tropical terrestrial ecosystems, limiting our understanding of the evolution of giant snakes and their relationship to climate in the past. Here we describe a boid snake from the oldest known neotropical rainforest fauna from the Cerrejón Formation (58-60 Myr ago) in northeastern Colombia. We estimate a body length of 13 m and a mass of 1,135 kg, making it the largest known snake. The maximum size of poikilothermic animals at a given temperature is limited by metabolic rate, and a snake of this size would require a minimum mean annual temperature of 30-34 °C to survive. This estimate is consistent with hypotheses of hot Palaeocene neotropics with high concentrations of atmospheric CO2 based on climate models. Comparison of palaeotemperature estimates from the equator to those from South American mid-latitudes indicates a relatively steep temperature gradient during the early Palaeogene greenhouse, similar to that of today. Depositional environments and faunal composition of the Cerrejón Formation indicate an anaconda-like ecology for the giant snake, and an earliest Cenozoic origin of neotropical vertebrate faunas.