1 Manuscript received 17 January 2013; revision accepted 1 February
2013.
The authors thank B. Meyer-Berthaud (CNRS-CIRAD Université
Montpellier II) and D. Wang (Peking University) for sharing images of
Xenocladia and Rotafolia ; and W. DiMichele, C. Hotton, and J. Wingerath
(Smithsonian Institution–NMNH) for facilitating the loan of fossil specimens.
S. Strayer, M. Nystrom, and T. Lloyd helped prepare acetate peels and
slides. Comments and suggestions from three anonymous reviewers
greatly improved the manuscript.