By examining these joints, ridges and knobs, and describing individual vertebrae as sets of coordinate points on a graph, Head and Polly created a template for all snakes. Over the course of evolution “snakes get bigger by adding more vertebrae,” Head said, and there can be as many as 300 vertebrae in the spinal column of a modern python, boa or anaconda. “But the big ones get more vertebrae only up to a point, then the vertebrae just get bigger.”
After developing coordinates for individual Titanoboa vertebrae, Head and Polly used the model to position them in their correct spinal location and determine Titanoboa’s length.The team published its first results in Nature in early 2009, saying Titanoboa was between 42 feet and 49 feet long, with a mean weight of 2,500 pounds. The Cerrejón vertebrae were all of comparable size even though they were from different animals. With Titanoboa, enormous was the rule, not the exception.
The Cerrejón team had found what appeared to be an authentic primeval monster. Titanoboa was as long as a school bus and weighed as much as a small rhino. Aside from the boid-style vertebrae, however, that was about all that could be said about the creature at first.
The discovery last year of the Titanoboa skull was key to advancing the research. “It’s not beautiful, but it’s a snake skull and there aren’t many of those,” Bloch said. “When we went down to Cerrejón, we thought ‘Well, pie in the sky we’ll find a skull of Titanoboa—’”
“—and then we did,” Head added.
They were sitting side by side in Bloch’s Gainesville office, in front of two microscopes. The process of assessing new bones from a fossil like Titanoboa is tedious and repetitive. They were comparing the contours of individual skull bones with exquisitely preserved modern boa, anaconda and python skulls from the university’s snake collections.
Bloch and Head wanted to determine if their first analysis—that Titanoboa was more boa than anaconda—would hold up. Fragments of jawbone suggested that Titanoboa’s mouth and whole head could have been over two feet long. A quadrate—a hinge bone connecting the lower jaw to the skull—enabled the back of the lower jaw to extend behind Titanoboa’s brain. Its mouth could “open big and open wide,” Head said.
There was at least one inconsistency, however. By looking at the number of holes in the jawbone fragments, Bloch and Head concluded that Titanoboa had more closely packed teeth than modern-day boas. “Is it more a specialized fish-eater?” Head asked. “If you’ve got lots of teeth, it’s easier to grab slippery, scaly fish.”
As far as Titanoboa was concerned, however, it probably did not matter. The crocs and the turtles undoubtedly ate fish, but Titanoboa was at the top of the food chain. It could eat fish, but it could also eat the crocs and turtles. “Some snakes—especially anacondas—can and do eat crocodilians,” Head said. “Still, wouldn’t it be strange if, instead of a monster, this is just a big, lazy snake that sits on the bottom grabbing fish as they swim by?”
Bloch laughed. “I don’t think so.”
Eventually they agreed that Titanoboa’s skull was different from that of other boas, but they couldn’t determine if the extinct animal was more closely related to a boa or anaconda.
The size of the snake immediately raised questions about how it got to be that big, and what it needed to survive. The Cerrejón team concluded in 2009 that Titanoboa had to have lived in a climate with a mean ambient temperature between 86 and 93 degrees Fahrenheit, substantially higher than the hottest average for today’s tropical forests, which is 82 degrees.
That assertion, Head acknowledged, “has been extremely controversial.”
For the past several years, the Titanoboa researchers and other experts have been trying to understand and model the climate that the giant snake lived in. There’s been some disagreement about how best to estimate the temperature 58 million years ago.