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Microfossil project at Petrified Forest uncovers the smallest secrets of the past

A man in a grey shirt swings a pickax at the ground in a dry, pebbly, gray, hilly landscape, with two other scientists in the distance.
Melissa Sevigny
Adam Marsh, Isiah McKinney, and Ben Kligman visit a fossil-rich site in Petrified Forest National Park.

A remarkable science project is underway at Petrified Forest National Park to uncover the forgotten creatures of the Triassic period. It’s a time best known as the dawn of the dinosaurs, but frogs, lizards, and other small animals have their origins in the Triassic, too. Discovering their story requires microscopes, tweezers, and a keen eye for the secrets of the past.

The colorful hills of Petrified Forest hide all kinds of hidden wonders, and paleontologist Adam Marsh is headed out to find them. He parks his truck not far from one of his field sites. "It's a hop, skip, and a jump over that ridge to where we're going," he says, pointing. Dark bands in the hills mark what used to be the bottom of Triassic ponds, some 200 million years ago. They’re full of microfossils.

Marsh says park paleontologists never used to pay attention to the little things, too busy digging up dinosaurs and crocodile-like creatures. He says that changed about a decade ago."It was sort of happenstance of preparing large fossils and finding the small stuff inside, and then kind of switching focus to realize: oh, we’re missing most of the story of diversity through time by focusing on the large stuff," he explains.

At the field site, Marsh digs his pickax into the hillside. A shower of tiny fossils falls out. "See how this is a coprolite, these are all little coprolites and teeth," he says, fishing through the fossils.

Coprolites are what’s left over after Triassic beasts used ponds and rivers as bathrooms. Studying these small roundish blobs is the specialty of park intern Isaiah McKinney.

"I had that dinosaur phase as a kid that I never really grew out of," McKinney jokes.

Coprolites might not be as glamorous as dinosaurs, but McKinney says their various shapes—spiral or pancake-flat—give clues to the anatomy of animals long since extinct. "Every part of the puzzle tells a story," he says. "And really it’s our goal as paleontologists to try to put that story together, even if it means looking at the not so pleasant stuff."

A man holds a screen full of mud in a trough of water.
Melissa Sevigny
Adam Marsh screenwashes a batch of microfossils

But how to find, say, a hipbone the size of eyelash? The team brings buckets of soil back to the museum laboratory at the Petrified Forest visitor center. There, Adam Marsh soaks the dirt in water until it turns to sludge. He carries a bucket outside to an old cattle trough filled with water, and pours the sludge into a submerged screened box.

"Here’s the fun part," Marsh says, demonstrating. "You basically agitate this to get the mud and the water to go through the bottom of the box, leaving bigger chunks of mud and hopefully all your fossils in the box."

Bones and teeth are picked out and cleaned up with tiny air hoses and paintbrushes. Broken pieces are jigsawed back together with tweezers under microscopes, plus dabs of superglue so small they could fit on the end of a human hair.

A cluttered desk with a microscope, laptop, and screen showing a magnified view of tiny bits of fossil bone.
Melissa Sevigny
Reassembling a broken fossil under a microscope

Seasonal paleontologist Ben Kligman is working on a reptile jaw. "It’s one of the big satisfying aspects, is when you do find a fit like that, that really opens a whole new world of understanding this animal," he says, describing how he puzzled the pieces of the jaw back together.

This ability to find and reassemble tiny broken bits of bone is a new step in paleontology. And it’s turning up all kinds of new species—like minuscule frogs and toothed worms—that still have descendants today.

Even more exciting, Kligman says, are the bones they can’t identify.

"There’s still a huge amount of the anatomy of all these animals that’s a mystery and will be probably unraveled over the next century," he says. "People will slowly figure out, bit by bit, what all these different bones we’re finding are."

The scientists say one drawer of microfossils can hold a career’s worth of data. And now that they know how to look, they’re finding Triassic troves not just in Petrified Forest, but in other places throughout North America—small wonders that have been overlooked until now.

An open drawer displays small white boxes with fossils of various shapes inside
Melissa Sevigny
Drawers of microfossils at Petrified Forest National Park

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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