About the Authors

Rebecca Fay Johnson


Affiliation Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, California, United States of America,

Terrence M. Gosliner

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: RFJ TMG. Performed the experiments: RFJ. Analyzed the data: RFJ. Contributed reagents/materials/analysis tools: TMG. Wrote the paper: RFJ. Conceptualized and wrote the new classification: TMG RFJ.