It was the mother of all snakes, a behemoth as long as a school bus and as heavy as a Volkswagen Beetle, that ruled the Amazon rain forest for 2 million years before slithering into nonexistence.

Now this monster has resurfaced in fossils taken from an open-pit coal mine in Colombia, a startling example of growth gone wild.

Modern boas and anacondas, which average less than 20 feet in length and reach a maximum of 30 feet, have been known to swallow Chihuahuas, cats and other small pets, but this prehistoric monster snacked on giant turtles and primitive crocodiles.

"This is amazing. It challenges everything we know about how big a snake can be," said herpetologist Jack Conrad of the American Museum of Natural History in New York, who was not involved in the research.

The estimated length, 43 feet, "is the same as the largest Tyrannosaurus rex that we know of, although it only weighs one-sixth as much," he added.

The find sheds light on snake evolution but also provides insights into climate. Because Titanoboa cerrejonensis, as it has been named, was coldblooded, the tropical climate had to be 6 to 8 degrees warmer than it is today for a snake that large to survive, said evolutionary biologist Jason Head of the University of Toronto Mississauga, lead author of a paper on the fossils appearing today in the journal Nature.

The fossils of several specimens of the snake are from a cache of fossils excavated from the Cerrejon coal mine in Colombia. Paleontologists are excited about the find because there are few fossils of tropical vertebrates from the period after the dinosaurs' demise 65 million years ago.

Bloch and his students found hundreds of specimens dug from the mine, including "the largest freshwater turtle ever known" and "beautifully preserved skeletons" of an extinct species of crocodile "known to have been in South America but never seen before."

They also found fish fossils, related to bone fish and tarpon, that would have lived in brackish seawater. "That indicates it was a big, riverine system close to the ocean," Bloch said.

Titanoboa was probably the largest nonmarine creature living on Earth during that period, Head said. The turtles and crocodiles that the team excavated were probably the giant snake's primary diet.

Snakes are generally able to swallow prey that weighs about the same as they do, Conrad said. Modern photos show reticulated pythons eating deer that weigh 120 to 150 pounds, he said. This snake, weighing 2,500 pounds, "could eat a large cow or a bison" — if there had been any around.

Extrapolating from the energy requirements of modern snakes, the team estimated Titanoboa required an average yearly temperature of 86 to 93 degrees Fahrenheit, higher than the modern average of about 83 degrees in coastal Colombia.

This expands on current theories about what happens at the equator during periodic bouts of natural global warming. One school of thought holds that temperatures at the equator are buffered, staying relatively constant while more northern latitudes heat up.