For almost 100 years, Apatosaurus was portrayed as a swamp-bound animal whose immense body was buoyed by water. In the 1960s, Bakker joined a handful of paleontologists who argued that the massive beasts were really more like elephants: all-terrain animals that could roam over the flood plain, through river channels and anywhere else they wanted to go.
Bakker, then an undergraduate at Yale, went to Morrison to see if Apatosaurus' habitat supported his idea that the beasts were mobile. But he and two students spent two years unsuccessfully hunting for Quarry 10, which aside from being partially filled in, as Bakker finally discovered, was also obscured by bullet cartridges, beer cans and other remnants of teenage outings.
Today, Bakker is sifting through Lakes' spoil pile—lumps of clay stone that the 1870s crew tossed aside—when someone in the pit excitedly calls for him. He scrambles down into the hole, where his bearded face lights up under his straw cowboy hat. The museum crew has uncovered what appear to be Jurassic-era castings of a small tree's root system. "This is a big deal," says Bakker, using a finely bristled brush to baste the knobby fossils with glue. "In ‘CSI' terms, that's the crime scene floor. Victim number one"—the Apatosaurus found in 1877—"lay buried just above."
The clue adds to evidence that Apatosaurus did not live in water. The team has found layers of sediment consistent with a small pond, but none of the crocodile or tortoise fossils typically found in swamps from the Jurassic Period more than 200 million years ago. This spot may have attracted generations of Apatosaurus, Bakker says, because it provided a watering hole on a dry wooded plain. "If there was a forest, there would be a lot more wood—and there isn't—and a lot more fossilized leaves—and there ain't. So it was a woodland but probably a lot like Uganda—hot tropical woodland that was dry for most of the year."
The most significant recent discoveries at the Morrison quarries have been dinosaur tracks. Early dinosaur hunters overlooked them. In Quarry 10 and another Lakes quarry less than a mile away, museum staff have recovered 16 Stegosaurus tracks. They include ten hatchling tracks—the first ever discovered. One rock appears to show four or five baby Stegosauri all heading in the same direction. Another boulder includes a partial juvenile Stegosaurus hind paw track that was stepped on by an adult Stegosaurus. "It suggests that Stegosaurus moved in multiple-age herds," says Mossbrucker, and adults may have cared for hatchlings.
The researchers have also found the world's first baby Apatosaurus tracks. They could change paleontologists' view yet again: the tracks are from the rear legs only, and they are spaced far apart. "What's really cool about these tracks is that the baby animal is functionally running—but it's doing this just on its back legs. We had no idea a Bronto could run, let alone scoot along on its hind legs like a basilisk," Mossbrucker says, referring to the "Jesus lizard" that appears to walk on water.
He and others speculate that adult Apatosauri, some of the largest animals ever to walk the earth, could prop themselves up on two legs with the help of their long tails. But others argue that it would have been physiologically impossible to pump blood up the animals' long necks or to raise their heavy front limbs off the ground.
Bakker and Mossbrucker say their goal is to look at Quarry 10 holistically—considering the local geography, climate, flora and fauna—to create a picture of where and how Jurassic dinosaurs lived. "I want to know as completely as I can what kind of forgotten world these dinosaurs knew," says Mossbrucker. "I want to see what they saw, touch their earth with my own feet and be in the Jurassic."
Bakker gestures toward the pit, where Libby Prueher, the museum's curator of geology, sifts soil alongside volunteer Logan Thomas, a high-school student with a passion for snakes. "It's weird that [Marsh and Cope] thought that dinosaurs were a zero-sum game, that Marsh thought, ‘If Cope got a bone, I lost a bone,'" says Bakker. The goal isn't to vanquish one's rivals, he says: "the guiding inspiration for studying the dead dinosaurs is to get back to how they lived."
Genevieve Rajewski, a Boston-based writer, caught dinomania as a child and is surprised by how much paleontology has changed.