The Kirtlandian is a North American land-vertebrate faunal age of the Cretaceous period, following the Judithian and succeeded by the Edmontonian. It lasted about 2 million years, ca 74.8 to 72.8 Mya and is characterized by the ceratopsian Pentaceratops sternbergii, which lived throughout the Kirtlandian. It was first named by R.M. Sullivan and S.G. Lucas in 2003 as a faunal age for the Kirtland and Fruitland formations. Previously, only five land-vertebrate ages were identified from the Late Cretaceous. as identified by Loris S. Russell in 1975, they include the Paluxian, Aquilan, Judithian, Edmontonian, and the Lancian. Before the naming of the Kirtlandian, three gaps, between the Paluxian and Aquilan, the Aquilan and the Judithian, and the Judithian and Edmontonian, were identified but not named.

The Fruitland Formation measures 97 to 107 metres (318 to 351 ft) thick, and with the 594 metres (1,949 ft) of the Kirtland Formation, the Kirtlandian consists of 701 metres (2,300 ft) of sediments. The rock types within the formations are primarily coal beds, but also include sandstone, siltstone, mudstone, and shale. Within the sediments with a Kirtlandian age, two local faunas, the Hunter Wash local fauna, and the Willow Wash local fauna, have been identified. The currently accepted date of the Kirtlandian is 74.8 to 72.8 million years ago. (see more...)