Thomas Richard Holtz Jr. (born September 13, 1965) is an American vertebrate palaeontologist, author, and principal lecturer at the University of Maryland's Department of Geology. He has published extensively on the phylogeny, morphology, ecomorphology, and locomotion of terrestrial predators, especially on tyrannosaurids and other theropod dinosaurs. He wrote the book Dinosaurs and is the author or co-author of the chapters "Saurischia", "Basal Tetanurae", and "Tyrannosauroidea"