The molluscan and brachiopod fauna of the Late Cretaceous Pierre Shale (Baculites compressus/Baculites cuneatus biozones) near Kremmling, Colorado

The Kremmling Paleontological Resource Area (KPRA) contains one of the most fossiliferous units within the Late Cretaceous Western Interior Seaway of North America. It was deposited during the late Campanian Baculites compressus/cuneatus ammonite biozones ((\approx) 72.5 Ma) and records slightly less than one million years of depositional history. Examination of the fauna, its dominant preservational mode and taphonomy as well as the lithologic evidence from measured stratigraphic sections strongly suggests that the depositional environment of the KPRA was a shallow, relatively nearshore environment. A detailed taxonomic examination of the molluscan fauna was undertaken in order to re-evaluate past work as well as to more thoroughly document the fauna. Samples were collected from 79 locations within the (\approx) 1 km² study area. The molluscan fauna from the KPRA consists of 47 bivalve, 22 gastropod, and 13 cephalopod species; ten of these species are new. In addition, two inarticulate brachiopods and one serpulid are described. This highly diverse assemblage points to an increase in nearshore diversity as compared to faunas described from earlier intervals with similar environmental settings. The timing of this increase in species richness remains elusive, but may have initiated in the late Campanian and continued into the early Maastrichtian