Colorado City Formation

The formation hosts the Otis Chalk fossil sites, named after a ghost town in Howard County.

[5] They occupy a narrow band of sediments between the slightly older Camp Springs Formation and much younger Cretaceous deposits.

The vast majority of fossils collected from the formation were recovered during a 1939–1941 state-sponsored Works Progress Administration paleontological survey.

[4] The Otis Chalk localities that are situated in the Colorado City Formation form the basis of the Otischalkian Land Vertebrate Faunachron (LVF), which is defined by the first appearance of Parasuchus.

[6] Other archosaur fossils include remains of an unnamed silesaurid[7] and a partial femur of a theropod or herrerasaurian dinosaur referable to the Chindesaurus + Tawa clade.