1. a Division of Paleontology, American Museum of Natural History , Central Park West at 79th Street, New York , NY , 10024 , USA E-mail:
2. b Lamont-Doherty Earth Observatory, Columbia University , 61 Route 9W, Palisades , NY , 10964 , USA
3. c Museum of Paleontology and Department of Integrative Biology , University of California , 1101 Valley Life Sciences Building, Berkeley , CA , 94720-4780 , USA
4. h Utah Museum of Natural History and Department of Geology & Geophysics , University of Utah , Salt Lake City , UT , 84112
5. d Division of Resource Management , Petrified Forest National Park, P.O. Box 2217, Petrified Forest , AZ , 86028 , USA
6. e Committee on Evolutionary Biology , University of Chicago , 402 Culver Hall, 1025 E. 57th Street, Chicago , IL , 60637 , USA
7. f Department of Geology , The Field Museum of Natural History , 1400 S. Lake Shore Drive, Chicago , IL , 60605 , USA
8. i Department of Anatomical Sciences , Stony Brook University , Health Sciences Center T-8 (040), Stony Brook , NY , 11794 , USA
9. g Department of Geological Sciences and Vertebrate Paleontology Laboratory , University of Texas , Austin , TX , 78712 , USA