How Snowmass Village became the improbable—and mysterious—site of a fossil mother lode that may redefine Colorado’s evolutionary history.
With any prehistoric discovery, there’s potential for hyperbole. But the numbers alone make the Ziegler site spectacular, and the mastodons are its crown jewels. It’s long been known that mammoths once roamed Colorado, even at elevation, but mastodons have never been found this high in North America—Ziegler Reservoir sits at almost 8,400 feet. Stranger still, Johnson says, the two are never found together.
To the layperson, mammoths and mastodons aren’t much different. Essentially, they’re both big, furry elephants. But finding them together is like discovering panda and polar bear remains in the same spot—they’re both bears, but they wouldn’t live in the same place at the same time. Mastodons and mammoths overlap in geologic time, but their diets—and therefore their habitats—are simply too disparate to find them side-by-side. Although they’re both vegetarians, the smaller mastodons were forest dwellers, while the larger mammoths were grassland grazers.
The orientation of the two species at Ziegler added to the mystery because the remnants of different time periods are stacked like pancakes below the lake. The mastodons lie in the lowest, oldest layers, embedded with trees. The mammoths reside at the top, where no trees remain, suggesting the tree line must have fallen and the climate cooled somewhere in between. “We’re seeing something that no one’s seen before,” Johnson says. It’s “the one place in North America where you can tell the story of ecosystems changing through time at high elevation.”
If the discovery of the elephantine specimens isn’t manna enough, consider this: The ancient plants and animals in the site are nearly pristine. Buried in peat and clay, the bones haven’t even petrified, giving scientists a shot at extracting DNA, à la Jurassic Park. “The preservation is staggeringly good,” Johnson says. “The leaves are still green. The trees still have bark on them. And the insects are still iridescent.”