About the Authors
- Jeffrey W. Martz, William G. Parker
- Division of Resource Management, Petrified Forest National Park, Petrified Forest, Arizona, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: JWM. Performed the experiments: JWM WGP. Analyzed the data: JWM WGP. Wrote the paper: JWM.