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GEOREF RECORD

Redescription of the Late Cretaceous (late Santonian) ammonite Desmoscaphites bassleri Reeside, 1927, from the Western Interior of North America

Neil H. Landman and William A. Cobban
Redescription of the Late Cretaceous (late Santonian) ammonite Desmoscaphites bassleri Reeside, 1927, from the Western Interior of North America
Rocky Mountain Geology (December 2007) 42 (2): 67-94

Abstract

The Late Cretaceous scaphitid ammonite Desmoscaphites bassleri Reeside, 1927, is redescribed based on newly collected material from Montana. This species is an important index fossil and demarcates the uppermost Santonian in the U.S. Western Interior. It is widely distributed and extends from Alberta to New Mexico, primarily along the western margin of the Interior Seaway. The adult shell is moderately stout and closely coiled, with small ventrolateral tubercles on the body chamber. Microconchs are smaller than macroconchs but otherwise similar in morphology. There is an abrupt change in ornamentation on the late juvenile whorls from coarse, widely spaced ribs to threadlike, more closely spaced ribs, with a pronounced sinuosity. The ribs later become more widely spaced on the shaft of the body chamber and more closely spaced again near the aperture. The early whorls are characterized by constrictions, which represent flexures in the shell wall. The constrictions first appear at a shell diameter of approximately 3 mm and occur regularly thereafter at intervals of 65-90 degrees up to a shell diameter of approximately 15 mm. The suture is characterized by a trifid first lateral lobe. This lobe does not pass through an asymmetrically bifid stage during ontogenetic development.


ISSN: 1555-7332
EISSN: 1555-7340
Serial Title: Rocky Mountain Geology
Serial Volume: 42
Serial Issue: 2
Title: Redescription of the Late Cretaceous (late Santonian) ammonite Desmoscaphites bassleri Reeside, 1927, from the Western Interior of North America
Affiliation: American Museum of Natural History, Division of Paleontology (Invertebrates), New York, NY, United States
Pages: 67-94
Published: 200712
Text Language: English
Publisher: University of Wyoming, Dept. of Geology and Geophysics, Laramie, WY, United States
References: 56
Accession Number: 2008-045193
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes three appendices
Illustration Description: illus. incl. chart, strat. col., sketch map
N44°30'00" - N49°00'00", W116°01'60" - W104°01'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, University of Wyoming. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200813
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