Paleontologist Matthew Lamanna can still remember the day in 2014 when a colleague, Hesham Sallam, emailed him detailed pictures of fossils that had just been unearthed by his team in Egypt. From one photo, depicting the remains of a large lower jaw bone, Lamanna knew right away that Sallam had found a dinosaur. “No pun intended, my jaw did almost literally hit the floor when I saw that,” Lamanna, the principal dinosaur researcher at the Carnegie Museum of Natural History, told The Washington Post. “When you stare at dinosaur bones for a lot of your life, you learn to recognize...