Paleontologist are like detectives who examine the evidence that extinct animals left behind. Those clues to what dinosaurs were like are found in fossils - the ancient remains of an organism, such as teeth, bones or shell - evidence of animal activity , such as footprints and trackways.
Some consider Bernum Brown , who began his carrier at the American Museum of Natural History in 1897 , to be one of the greatest dinosaur hunters in the late 19th and early 20th centuries. Many of his greatest discoveries , including the first specimens of Tyrannosauras rex ever found, are on display in the Museum dinosaurs halls.