About the Expedition

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Wyoming, USA
© The Field Museum, GEO86416_127d, J. Weinstein
Green River Fossils
© The Field Museum, GN90602_194D, J. Weinstein.
Fossil Butte, Wyoming
© A. Shinya
The Stones & Bones Class

The Green River Formation contains sediments from one of the world's longest-lived great lake systems, which once covered part of the western United States. As part of this formation, deposits from ancient Fossil Lake can be found in what is now southwestern Wyoming. These rich deposits provide the best record ever discovered of an entire ecosystem frozen in time, allowing us a rare glimpse of what life was like more than 50 million years ago.

The beautifully preserved remains of hundreds of plants and animals reveal the ancestors of many living and extinct species. From their lifelike poses, we can witness the interactions between species within the Fossil Lake community and observe their feeding habits, life stages, and more!


Field Museum Excavations
Revered as a "paleontological mother-load" and hailed as a national treasure, the Fossil Butte Member of the Green River Formation (the official geological classification for Fossil Lake deposits) has been excavated for more than 140 years by professional paleontolgists and commerical fossil excavators alike.

Dr. Lance Grande has been excavating sites within the Fossil Butte Member for more than three decades. Each year, he has taken a team of fossil preparators, volunteers, and students to search for more specimens in the Tynsky Quarry on the Lewis Ranch near Kemmerer, Wyoming. Thanks to Dr. Grande's efforts, The Field Museum currently boasts the world's largest and most extensive collection from the Fossil Butte Member of the Green River Formation!

The “Stones & Bones” Class
For many years, Dr. Grande has brought students from his University of Chicago Graham School course, called “Stones and Bones,” to assist in excavations at the site. The four-week course for advanced high school students begins with a week at The Field Museum exploring evolutionary themes and paleontological methods, followed by two weeks of hands-on fieldwork as part of Dr. Grande’s team, and a final week back at the Museum learning to prepare and analyze the collected material and incorporate it into our permanent collections.

Altogether, it’s great training for future scientists, who get to participate in the discovery process and experience daily life on a dig working with professional paleontologists and other scientific staff. And it’s a terrific opportunity for students to see science in action—each new fossil find reveals evolutionary relationships between living and ancient animals and paints a clearer picture of life more than 50 million years ago.

To learn more about Green River fossils, explore the stories in "About the Expedition," and be sure to check out Dr. Grande's photo galleries, videos, and blogs from his 2008 expedition with the "Stones and Bones" class.