Pliensbachian (Lower Jurassic) Biostratigraphy and Ammonite by R. C Thomson

By R. C Thomson

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Extra info for Pliensbachian (Lower Jurassic) Biostratigraphy and Ammonite Fauna of the Spatsizi Area, North-Central British Columbia

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40, PI. 10, figs. 16-20. 1964a 71968 The Spatsizi specimen was found at locality 66. 1981 A g e. Late Pliensbachian (Kunae Zone). 1981 Genus A rieticeras Oppel, 1862 1896 1931 M aterial. Thirty specimens preserved as fragmental external and internal moulds in calcareous concretions and siltstone. Seguenziceras, Levi M eneghinia Fucini T y p e species. A m m o n ite s algo via n u s O ppel, (p. 137), by original designation. 1862 R e m a rk s. Shell evolute, whorl section elliptical to quadrate.

4, f i g s . ) 71968 Fuciniceras cf. F. acutidorsatum Kovacs. Imlay, p. 41, PI. 7, figs. 22 and 24 only, cf. 1977 A r i e t i c e r a s r u t h e n e n s e ( R e y n e s ) . Wiedenmayer, p. 85, PI. 16, fig. 17; PI. 17, fig. 3 (and synonymy), cf. 1980 A r i e t i c e r a s r u t h e n e n s e ( R e y n e s ) . Wiedenmayer, p. 115, PI. 20, figs. 21-24; PI. 21, figs. 1, 2. M aterial. Nine specimens, poorly to moderately well preserved as external and internal m oulds in calcareous concretions. M easurem ents.

Fla n k s flat to slightly convex. Ventral shoulder abruptly rounded; venter low, slightly convex. O rnam ent consists o f dense ribs, which arise on the umbilical wall where they trend rursiradiately, then form a slightly flexuous pattern across the flanks to elongate ventrolateral tubercles, beyond which they fade rapidly on the venter. The genus Dubariceras was created to accom m odate certain Lower Pliensbachian ammonites o f T ethyan aspect that previously had been assigned to the genera U ptonia, P latypleuroceras, and D ayiceras (family Polymorphitidae).

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