1. Committee On Evolutionary Biology, The University of Chicago, Chicago, IL 60637 U.S.A.,
2. Department of Ecology and Evolutionary Biology and Biodiversity Institute, University of Kansas, Lawrence KS 66045 U.S.A.,
3. Section of Paleontology, Institute of Geosciences, Universität Bonn, 53115 Bonn, Germany,
4. Department of Organismal Biology and Anatomy, Committee On Evolutionary Biology, The University of Chicago, Chicago, IL 60637 U.S.A.,