1. Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA.
2. L. H. Bailey Hortorium, Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA.
3. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Museo Paleontológico Egidio Feruglio, 9100 Trelew, Chubut, Argentina.