Making The Paper

摘要

Palaeontologists have long been searching for additional clues to the evolution of tropical vertebrates in the wake of the dinosaurs' demise roughly 65 million years ago. Sixty-million-year-old rock in the Cerrejon Coal Mine of northeastern Colombia yielded an exciting find - fossils of the largest snake species ever seen. These offered an opportunity to exploit reptile biology for palaeoclimatic clues. A team of palaeontologists has been studying the mine's rocks for several years. Massive tractors are used deep below the surface to excavate long, thick coal seams that can spontaneously combust. "The mine itself resembles Dante's Inferno, but it is heaven for a fossil collector," says Jonathan Bloch, a vertebrate palaeontologist at the Florida Museum of Natural History in Gainesville and one of the team that discovered and identified the snakes' giant vertebrae. Bloch contacted Jason Head, an expert on fossil snakes at the University of Toronto in Mis-sissauga, Canada. Head jumped out of his seat when he saw the specimens. "When you look at fossil snake vertebrae bigger than your hand, you soon realize that their size alone is shedding new light on this past ecosystem," says Head. Even before they had an accurate estimate of the snakes size, he and his colleagues began to question what it said about past climate. Plant fossils or ratios of oxygen and carbon isotopes are usually used as proxy data to interpret past climate. But cold-blooded vertebrates add a novel biological indicator because their metabolic rate controls their maximum size at a given temperature. "In this regard, the reptile fossil record is uniquely important and incredibly understudied," says Head.