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
Cephalopods from the Coniacian part of the Mancos Shale
Forresteria alluaudi (Boule,
Lemoine & Thevenin) 1907
Peroniceras dravidicum (Kossmat)
1895
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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