National Geographic : 2014 May
Digging Utah’s Dinosaurs 79 twining up the trees. We’ve also found lily pads and water lettuce, so we know there were ponds here with floating vegetation. And big rivers. Think of the Amazon, where you have the main channel of the river but also side chan- nels and lakes that are so filled with tannin they turn black. That’s probably what the little pond looked like that this leaf fell into.” The vegetation could have been so thick and lush in this part of Laramidia that there was no need for animals to wander very far, Miller speculated. Perhaps even the largest duck-billed dinosaur was able to get its fill within a relatively small range. That’s what you see today in tropi- cal rain forests, he said: many species sharing the same small spaces. The whole continent could have been organized as a series of eco- logical zones at different latitudes, each defined by varying amounts of precipitation or sunlight and each supporting its own set of dinosaurs. You wouldn’t need a physical barrier to explain the explosion of new species. “We haven’t done enough work yet,” Miller said. “In many respects it’s still a hunch. But if we’re right, and there were these small provin- cial populations that weren’t moving around, not interacting with other populations, you could have sexual selection happening very rapidly.” The lush landscape that would have made this possible was more like the swamplands of Louisiana than what you see here today, Samp- son said. But any such comparison is necessar- ily flawed, he added, because the Earth was so different 75 million years ago. “We’re still really in the dark when it comes to understanding the ecological dynamics.” That’s why he and his team return season after season to the Utah badlands, where every trek into the desert sheds new light on Laramidia’s story. “Every rock you crack open, you’re saying, Oh my God, I’ve never seen that before,” Miller said. “It’s brand-new. Unknown to science.” j these theropod tracks, up to 17 inches long, cross flag Point near Kanab. they’re relics of an era 100 million years be- fore Laramidia became an island—and evidence that, in the american West, dinosaurs ruled for a very long time. n Society Grant the research of the team of scientists in this story was funded in part by your National Geographic Society membership.