At Ukhaa Tolgod, in the Gobi Desert of Mongolia, lies what is billed as one of the greatest Cretaceous fossil finds in history. Starting in 1993, the discoveries have included the remains of more than 13 troodontid skeletons, over 100 uncollected dinosaur specimens; numerous mammals, and a nest-brooding adult Oviraptor. The reason for the huge number and extraordinary states of preservation is thought to be due to a series of catastrophic occurrences. These events swiftly buried the animals, precluding any damage by the elements or scavengers. Scientists believe normally stable sand dunes became drenched with rain water, triggering sudden debris flows that trapped—and preserved—the animals.