It also marked the start of a war between the two that became increasingly bitter, underhand, and often ridiculous. They sometimes stooped to one team's diggers throwing rocks at the other team's. Cope was caught at one point jimmying open crates that belonged to Marsh. They insulted each other in print and each poured scorn on the other's results. Seldom—perhaps never—has science been driven forward more swiftly and successfully by animosity.

Over the next several years the two men between them increased the number of known dinosaur species in America from 9 to almost 150. Nearly every dinosaur that the average person can name—stegosaurus, brontosaurus, diplodocus, triceratops—was found by one or the other of them. The notable exception being the Tyrannosaurus rex, which was found by Barnum Brown in 1902. Unfortunately, they worked in such reckless haste that they often failed to note that a new discovery was something already known. Between them they managed to "discover" a species calledUintatheres anceps no fewer than twenty-two times. It took years to sort out some of the classification messes they made. Some are not sorted out yet.