Bulletin 114—Contributions to Late Cretaceous paleontology and stratigraphy of New Mexico

By W. A. Cobban, W. J. Kennedy, and S. C. Hook, 1988, 44 pp., 2 tables, 27 figs.

Other publications in this series are Circulars 180, 185, 195, and Bulletin 122. The three chapters are titled: The Late Cretaceous ammonite Spathites Kummel and Decker in New Mexico and Trans-Pecos Texas; The Late Cretaceous ammonite Romaniceras Spath, 1923, in New Mexico; Middle Cenomanian (Late Cretaceous) molluscan fauna from the base of the Boquillas Formation, Cerro de Muleros, Doña Ana County, New Mexico. Enhanced by beautiful figures, this volume continues the series on Cretaceous paleontology and stratigraphy.

The first chapter in this bulletin, by W. A. Cobban, deals with Spathites. The genus Spathites was proposed by Kummel and Decker for medium-sized, stout, involute ammonites that have inner whorls ornamented by ribs and tubercles and outer whorls with reduced ornament. The suture is simplified. Kummel and Decker based their genus on S. chispaensis, which they described as a new species from trans-Pecos Texas and Chihuahua, Mexico. The second chapter, by W. J. Kennedy and W. A. Cobban, covers the ammonite Romaniceras. Romaniceras, represented by R. mexicanum Jones and R. sp., has been found in two areas of north-central NM. Most specimens, as well as the best preserved ones, occur in silty, calcareous concretions in the Semilla Sandstone Member of the Mancos Shale or a little below that member in the Rio Puerco valley northwest of Albuquerque. Other specimens have been found in septarian limestone concretions in the Blue Hill Member of the Carlile Shale in the Canadian River valley east of Springer. Ammonites associated with Romaniceras in NM include Prionocyclus hyatti, Hoplitoides sandovalensis Cobban and Hook, Coilopoceras springeri Hyatt, and Spathites puercoensis. A middle Turonian age is assigned.

The third chapter, written by W. J. Kennedy, W. A. Cobban, and S. C. Hook, talks of the molluscan fauna from Doña Ana County, NM. A thin bed of calcarenitic and coquinoidal limestone forms the base of the Boquillas Formation and rests disconformably on the lower Cenomanian Buda Limestone. This bed contains a fauna that indicates the zone of Acanthoceras amphibolum Morrow. The following stratigraphically important molluscan fossils are described and illustrated: Desmoceras sp., Moremanoceras straini sp. nov., Acanthoceras amphibolum Morrow, Cunningtoniceras cf. johnsonianum, Paracompsoceras landisis Cobban, Tarrantoceras sellardsi, Anisoceras cf. plicatile, Turrilites acutus Passy, Ostrea beloiti Logan, and Inoceramus arvanus Stephenson.