Large scaphitid ammonites (Hoploscaphites) from the Upper Cretaceous (upper Campanian-lower Maastrichtian) of North America : endless variation on a single theme

Title Variants

Alternative: Hoploscaphites from the Upper Cretaceous

Related Titles

Series: Bulletin of the American Museum of Natural History, no. 441

By

Landman, Neil H. , author

Kennedy, W. J. (William James) , author
Grier, Joyce C. , author
Larson, Neal L. , author
Grier, James W. , author
Linn, Tom. , author
Tackett, Lydia, , author
Jicha, Brian R., , author

Type

Book

Material

Published material

Publication info

[New York], American Museum of Natural History, [2020]

Notes

"Issued September 14, 2020."

Contents: 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.

Subjects

Ammonoidea , Bearpaw Formation , Cretaceous , Mollusks, Fossil , North America , Paleontology , Pierre Shale , West (U.S.)

Call Number

QH1 .A4 no.441 2020

Language

English

Identifiers

DOI: https://doi.org/10.1206/0003-0090.441.1.1
OCLC: 1195551318