Sphenodiscus beecheri w/ Exposed Sutures

Fox Hills Formation, Hoploscaphites nebrascensis Zone,

Upper Maastrichtian, Late Cretaceous,

Dewey County, South Dakota, USA

Fox Hills Formation Member, Zone and ammonite fauna

~ 66.5 MY

Timber Lake Member

Hoploscaphites nebrascensis Range Zone

Cucullaea Assemblage Zone: Hoploscaphites comprimus, H. nebrascensis, Discoscaphites gulosus, D. rossae, Baculites larsoni, Sphenodiscus beecheri, S. splendens

Sphenodiscus Assemblage Zone: Baculites larsoni, Discoscaphites conradi, D. gulosus, D. rossae, Hoploscaphites comprimus, H. nebrascensis, Sphenodiscu beecheri, S. splendens