Ammonite Zonation - Western Interior
100.25 - 68.69 Ma
Geologic Time
Phanerozoic
Mesozoic
Cretaceous
Late Cretaceous
Maastrichtian
Campanian
Santonian
Coniacian
Turonian
Cenomanian
Zone
Jeletzkytes nebrascensis
Hoploscaphites nicolleti
Hoploscaphites birkelundae
Baculites clinolobatus
Baculites grandis
Baculites baculus
Baculites eliasi
Baculites jenseni
Baculites reesidei
Baculites cuneatus
Baculites compressus
Didymoceras cheyennense
Exiteloceras jenneyi
Didymoceras stevensoni
Didymoceras nebrascense
Baculites scotti
Baculites reduncus
Baculites gregoryensis
Baculites perplexus
Baculites sp. (smooth II)
Baculites asperiformis
Baculites maclearni
Baculites obtusus
Baculites sp. (weak flank ribs)
Baculites sp. (smooth)
Scaphites hippocrepis III
Scaphites hippocrepis II
Scaphites hippocrepis
Scaphites leei
Desmoscaphites bassleri
Desmoscaphites erdmanni
Clioscaphites choteauensis
Clioscaphites vermiformis
Clioscaphites saxitonianus
Scaphites depressus
Scaphites ventricosus
Scaphites preventricosus
Scaphites mariasensis
Prionocyclus germari
Scaphites nigricollensis
Scaphites whitfieldi
Scaphites warreni
Prionocyclus macombi
Prionocyclus hyatti
Collingnoniceras praecox
Collingnoniceras woollgari
Mammites nodosoides
Vascoceras birchbyi
Pseudaspidoceras flexuosum
Watinoceras devonense
Nigericeras scotti
Neocardioceras juddii
Burroceras clydense
Sciponoceras gracile (Euomphaloceras septemseriatum)
Sciponoceras gracile (Vasoceras diartianum)
Dunveganoceras conditum
Dunveganoceras albertense
Dunveganoceras problematicum
Dunveganoceras pondi
Pleisacanthoceras wyomingense
Acanthoceras amphibolum
Acanthoceras bellense
Acanthoceras muldoonense
Acanthoceras granerosense
Conlinoceras tarrantense - Conlinoceras gilberti
Neogastroplites maclearni
Neogastroplites americanus
Neogastroplites muelleri
Neogastroplites cornutus
Neogastroplites haasi
