The age of the Nemegt is not known for certain , but it is commonly thought to belong to the Maastrichtian stage of the Late Cretaceous Period . , and Adasaurus would therefore have lived between 72 and 66 million years ago .
The age of the Nemegt , like most of Mongolia 's Late Cretaceous sediments , is not known for certain , but it is commonly thought to belong to the Maastrichtian stage of the Late Cretaceous Period .