Late Early Coniacian (Late Cretaceous) Ammonites

Coniacian age cephalopods are rare in Utah's rocks, they are found in isolated concretions in the Mancos Shale in the Vernal and Emery areas and in it's equivalents near Manti and the Kaiparowits Plateau. These rocks were deposited in the Sevier Foreland Basin.

References: Reeside, J. B., Jr., 1932, The Upper Cretaceous Ammonite Genus Barroisiceras in the United States, U.S.G.S. Professional Paper 170; Cobban, W. A., 1951, Scaphitoid Cephalopods of the Colorado Group, U.S.G.S. Professional Paper 239; Cobban, W. A., 1976, Ammonite Record from the Mancos Shale of the Castle Valley-Price-Woodside Area, East-Central Utah, B.Y.U. Geology Studies Vol.22, Pt.3; Kennedy, W. J., and Cobban, W. A., 1991, Coniacian Ammonite Faunas from the United States Western Interior, The Palaeontological Association (London), Special Papers in Palaeontology No. 45

common cephalopods
Cephalopods from the Coniacian part of the Mancos Shale

Forresteria alluaudi (Boule, Lemoine & Thevenin) 1907

Peroniceras dravidicum (Kossmat) 1895

Coniacian scaphites
Top: Scaphites preventricosus
Cobban 1951
Lower left: Yezoites frontierense
(Cobban) 1951   Lower right: Scaphites impendicostatus Cobban 1951

Scaphites preventricosus Cobban 1951
68mm long

Allocrioceras hazzardi
Young 1963

Eutrephoceras n. sp., 60mm dia., a Nautilid

Top from Left: Placenticeras fritschi de Grossouvre 1894, 80mm dia., Allocrioceras hazzardi Young 1963,
Baculites mariasensis Cobban 1951
Middle Right: ?Harleites castellense Reeside 1932, Probably a form of Forresteria alluaudi.
Bottom from Left: Yezoites frontierensis (Cobban) 1951, Peroniceras dravidicum (Kossmat) 1895,
Forresteria alluaudi (Boule, Lemoine & Thevenin) 1907.

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