مؤلف: Michael J. Ryan

Michael J. Ryan is Vice-Chair Curator and Head of Vertebrate Paleontology at the Cleveland Museum of Natural History. Brenda J. Chinnery-Allgeier is Lecturer in the School of Biological Sciences at The University of Texas at Austin. David A. Eberth is a senior research scientist at the Royal Tyrrell Museum in Drumheller, Alberta, Canada.