The Dakota Group rank is employed along the territory of the Dakota Hogback in Colorado and Wyoming, the Colorado Plateau, the Dry Cimarron River, and the Denver Basin. This group ranking recognizes sequences and members that exhibit local formational characteristics, especially marine shales that are less developed or absent further from the center of the seaway. As these locations were at the time of formation the earliest and deepest areas of the seaway, these groups can include older ages of rocks than are usually included elsewhere under the Dakota name. The names of the member formations of the Dakota Group vary between these regions as the geology there is studied further; but, the earliest unit included in Dakota Groups, excluded elsewhere, is the terrestrial Lytle Formation, which is older than any other Cretaceous rock in Colorado or Kansas. The Skull Creek Shale and Plainview Sandstone of Colorado are also included in the Dakota Group, as is the Cedar Mountain Formation of Utah and its Buckhorn Conglomerate member. However, these units represent a separate seaway sequence in the time between the Lytle and Dakota sequences, and in the plains to the east, the same units are named Kiowa Shale and Cheyenne Sandstone, which are considered separate from the Dakota Formation and do not appear at the type location.