Fossils of an indeterminate
Coriops species are known as early as the
Cenomanian of the
Naturita Formation in
Grand Staircase-Escalante National Monument in
Utah, USA. During the
Maastrichtian, remains of
C. amnicolus are abundant and widespread in the
Hell Creek Formation of Montana, the Dakotas, & Wyoming. Even younger
Coriops vertebrae were previously thought to have been identified from a
Late Paleocene-aged locality of the
Ravenscrag Formation in
Saskatchewan, Canada. However, a re-analysis of these vertebra found them to instead more likely belong to the osteoglossomorph
Lopadichthys, previously described from the Paleocene of Canada. The wide distribution of
Coriops in the North American interior, its disappearance and reappearance in southern regions such as Utah, and its general higher abundance in high latitude formations over lower latitude ones, suggests that it may have been a northernly-distributed species whose range repeatedly expanded south during cooler climactic intervals. == See also ==