Agate Fossil Beds National Monument
World-important Miocene bonebeds share the landscape with the James H. Cook collection and enduring histories of Lakota friendship and exchange.
Artwork inspired by Robert F. Gilder
Agate is famous for concentrated fossils of mammals such as *Menoceras*, *Dinohyus*, and the burrowing beaver relative *Palaeocastor*. The “Devil’s Corkscrews” are fossil burrow casts, a reminder that trace fossils can reveal behavior and habitat even when bones are absent.
The Cook Collection adds a separate, essential story: objects given to rancher James Cook by Lakota people must be understood through named relationships, cultural attribution, and consultation—not as decorative accompaniment to fossils. Walk a trail only after the visitor center establishes both histories.
- Age
- Early Miocene fossils
- Signature evidence
- Bonebeds and spiral burrow casts
- Cultural collection
- Lakota gifts associated with James Cook
Quick guide
- Interpretive pair
- Early Miocene fossils ↔ Bonebeds and spiral burrow casts
- Closing move
- Read Lakota gifts through named relationships, makers, and cultural attribution.
Quick guide
- Bonebeds
- Compare clustered mammal fossils with what sediment reveals about their burial.
- Trace fossils
- Use the spiral Palaeocastor burrows to recognize behavior preserved without bones.
- Cook Collection
- Read Lakota gifts through named relationships, makers, and cultural attribution.
- Trail
- Walk only after the visitor center establishes both paleontological and human histories.
Good to know
The spiral “Devil’s Corkscrews” are fossilized burrow casts, proving that traces of behavior can explain an ancient ecosystem even when no bones remain inside.
Notice these
- Early Miocene fossils
- Bonebeds and spiral burrow casts
- Lakota gifts associated with James Cook