1. Division of Paleontology, Institute of Geoscience, University of Bonn, Nußallee 8, 53115 Bonn, Germany;
2. W. M. Keck Science Department, Claremont McKenna, Scripps, and Pitzer Colleges, Keck Science Center, 925 N. Mills Avenue, Claremont, CA 91711-5916, USA;
3. Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA;
4. Institute of Anatomy, University of Bonn, Nussallee 10, 53115 Bonn, Germany