During that expedition, in 2004, the researchers grabbed everything they saw, and everything was big: ribs, vertebrae, parts of a pelvis, a shoulder blade, turtle shells more than five feet across. They found bits of dyrosaur and turtle everywhere, and other animals as well, but the team could not sort everything immediately. They put what they could in plastic bags, then dug pits and cast the big pieces in plaster of Paris.
“It’s like prospecting,” Bloch said. Walk along with brushes and tweezers and eyes focused on the ground until you find something you want. Put the little bits in plastic bags and label them. Mark the bigger pieces on a GPS device and come back the next day with plaster and a tarp. Wait too long, and the GPS reading is useless: The rain is a curse, washing everything down the slope, never to be seen again. But the rain is also a blessing, for when it stops, a whole new fossil field lies open for exploration.
For the next five years, Bloch and Jaramillo led field trips to Cerrejón and sent a steady stream of vertebrate fossils to Gainesville. Many of the remains looked a bit like those from modern animals, only much bigger. One new species of turtle was five and a half feet long, 67 percent larger than today’s biggest Amazon river turtles.
Although there are no modern dyrosaurs to compare with the fossils, University of Florida graduate student Alex Hastings described three new species, one of which was between 15 and 22 feet long. Another beast was a “dietary generalist,” Hastings said, who “could eat the large turtles.” It had huge jaws and a “death bite” that could penetrate the shell 1.5 feet in from its edge. “These are big animals.”
In 2007, Hastings was inspecting a shipment of fossils labeled “crocodile” and noticed a strange—and very large—vertebra. To his trained eye, it was clearly “not from a croc.” He showed it to fellow graduate student Jason Bourque, a fossil conservationist and reptile specialist.
“That’s a snake,” Bourque said. He delved into the university’s reptile collections and came up with the vertebra of an anaconda. It was smaller but reasonably close in appearance to the fossil. Bloch, Hastings and the rest of the team began ransacking the Cerrejón specimens. Fresh expeditions visited La Puente to search for more pieces of fossil snake. Eventually the team collected 100 snake vertebrae from 28 different animals.
“We’d had some of them for years,” Bloch said. “My only excuse for not recognizing them is that I’ve picked up snake vertebrae before. And I said, ‘These can’t be snake vertebrae.’ It’s like somebody handed me a mouse skull the size of a rhinoceros and told me ‘That’s a mouse.’ It’s just not possible.”
Except, apparently, it was. “I needed to know how big the snake was, so I called the only guy in the world who would be able to tell me,” Bloch said. That was Jason Head, then working at the University of Toronto. They had met in the early 1990s when Bloch was a graduate student at the University of Michigan and Head was an undergraduate.
Bloch gathered up “a whole bunch” of bone samples, carried them into his office and called up Head for a computer iChat. He held up a vertebra so Head could see it. Was this a snake?
“I’m buying my ticket tonight,” Head said.
Head spent several days in Gainesville with the Cerrejón researchers. They focused on the vertebrae from two different fossil snakes. Head noticed immediately that the creature had a T-shaped spine and that the bones had a number of characteristics that were unique to “boid” snakes—the lineage that includes boa constrictors and anacondas.
Both species are common in South America today. Boas can be up to 14 feet long and weigh as much as 100 pounds. Anacondas can exceed 20 feet and weigh more than 500 pounds. The bones of the Cerrejón snake suggested it was closely related to boas, but the Cerrejón environment offered a lifestyle more like that of the modern South American anaconda, a water dweller comfortable in both swift-moving rivers and swamps. And even though anacondas are big, these snakes were much bigger.
How big? The problem with sizing ancient snakes is that you never have the whole spine in a neatly articulated row. You get individual bones, maybe pairs and occasionally three together. And unless you can place individual vertebrae in their correct position along the spine, you cannot know the animal’s length.
Head and Indiana University paleontologist P. David Polly for two years had been building a mathematical model of a snake spinal column based on living species. Snake vertebrae, as Polly explained, are “lovely and complicated, and there are some characteristics that are common to all snakes.”