Browsing by Author "Grier, Joyce C."
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Item Description of two species of Hoploscaphites (Ammonoidea, Ancyloceratina) from the Upper Cretaceous (Lower Maastrichtian) of the U.S. Western Interior. (Bulletin of the American Museum of Natural History, no. 427)(American Museum of Natural History., 2019-02-22) Landman, Neil H.; Kennedy, W. J. (William James); Larson, Neal L.; Grier, Joyce C.; Grier, James W.; Linn, Tom.Two species of scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (lower Maastrichtian) of the Western Interior of North America are described. Hoploscaphites macer, n. sp., is medium size, with coarse ribs on the phragmocone, which become finer on the body chamber, and closely spaced ventrolateral tubercles. It occurs in the upper part of the Baculites baculus Zone and lower part of the overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, and Colorado, and in the Bearpaw Shale in Montana. Hoploscaphites criptonodosus (Riccardi, 1983) is larger and more coarsely ornamented, including one or two rows of lateral tubercles on the flanks of the phragmocone. It occurs in the upper part of the Baculites baculus Zone and overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, Colorado, and possibly South Dakota, and in the Bearpaw Shale in Montana and Saskatchewan, Canada. Both species form part of an evolving lineage of Hoploscaphites that first appears in the Western Interior of North America in the middle Campanian.Item Large scaphitid ammonites (Hoploscaphites) from the Upper Cretaceous (upper Campanian-lower Maastrichtian) of North America : endless variation on a single theme. (Bulletin of the American Museum of Natural History, no. 441)(American Museum of Natural History., 2020-09-14) Landman, Neil H.; Kennedy, W. J. (William James); Grier, Joyce C.; Larson, Neal L.; Grier, James W.; Linn, Tom; Tackett, Lydia; Jicha, Brian R.We describe three species of large scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (upper Campanian-lower Maastrichtian) of the Western Interior of North America. Each species occurs as two dimorphs, referred to as macroconch and microconch. All three species share a similar pattern of ornamentation consisting of long, thin, nonbifurcating ribs on the adoral part of the phragmocone, suggesting that they constitute a single monophyletic clade. Macroconchs of Hoploscaphites crassus (Coryell and Salmon, 1934) are characterized by a globose whorl section, with closely spaced ventrolateral tubercles on the body chamber, usually persisting to the aperture. Macroconchs of Hoploscaphites plenus (Meek and Hayden, 1860) differ from those of H. crassus in having a more subquadrate whorl section with flatter flanks, and fewer, larger, and more widely spaced ventrolateral tubercles. Macroconchs of Hoploscaphites peterseni, n. sp., closely resemble those of H. crassus, but differ in being nearly circular in side view with a more compressed whorl section. All three species lived at approximately the same time in the same general area and depositional environment. They are abundant in the Baculites baculus Zone but also occasionally occur in the B. eliasi Zone and possibly lower part of the B. grandis Zone. They are present in the Pierre Shale of east-central Montana and east-central Wyoming, the Lewis Shale of south-central Wyoming, and the Bearpaw Shale of northeast Montana. It is possible that these three species represent subspecies within a single species or a "flock" of very closely related species, similar to the "species flocks" observed in modern cichlid fishes.Item Supplemental Material for 'Large scaphitid ammonites (Hoploscaphites) from the Upper Cretaceous (upper Campanian-lower Maastrichtian) of North America : endless variation on a single theme. (Bulletin of the American Museum of Natural History, no. 441)'(American Museum of Natural History., 2020-09-14) Landman, Neil H.; Kennedy, W. J. (William James); Grier, Joyce C.; Larson, Neal L.; Grier, James W.; Linn, Tom; Tackett, Lydia; Jicha, Brian R.Supplemental Material for 'Large scaphitid ammonites (Hoploscaphites) from the Upper Cretaceous (upper Campanian-lower Maastrichtian) of North America : endless variation on a single theme. (Bulletin of the American Museum of Natural History, no. 441)'