This book idea was suggested by my supportive editor at Columbia University Press, Patrick Fitzgerald. I thank him and Kathryn Jorge at Columbia University Press, along with Ben Kolstad at Cenveo, for all their hard work on the book. Most of the illustrations were generously provided by my colleagues who are acknowledged as appropriate in the captions. I thank Drs. Thomas Holtz, Darren Naish, and Hans-Dieter Sues for providing a careful scientific review of the entire book; and Daniel J. Chure, William Hammer, and John Foster for reading certain chapters in areas of their expertise. I particularly thank my youngest son, Gabriel, who is even crazier about dinosaurs at his young age than I ever was; he gave me helpful feedback on certain chapters. I thank my two other sons, Erik and Zachary, for their love and support on this project as I disappeared in front of my computer for one and one-half months in winter 2017–2018 to write this book. I especially thank my amazing wife, Dr. Teresa LeVelle, for her encouragement and support on this project, especially when my hands were stiff with carpal tunnel syndrome every night after writing a 4,000- to 5,000-word chapter every day.