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The Eocene ischyromyid rodent Thisbemys from the Washakie Formation, Wyoming (early Eocene, late Bridgerian) with comments on the systematics of the genus

William W. Korth
The Eocene ischyromyid rodent Thisbemys from the Washakie Formation, Wyoming (early Eocene, late Bridgerian) with comments on the systematics of the genus
Journal of Paleontology (November 2020) 94 (6): 1180-1190

Abstract

A large sample (>100 specimens) of the fossil rodent Thisbemys Wood, 1959, from the early Eocene (late Bridgerian; Br3) Washakie Formation of Wyoming is described. Two species are recognized: a new species, T. intermedius n. sp., and Thisbemys cf. T. uintensis (Osborn, 1895). The large sample size of the former has allowed for a detailed study of variation in size and morphology within the species based on tooth-wear. As a result, some systematic changes in the species included in this genus are suggested: (1) T. brevicrista Ostrander, 1986, is limited to the holotype, and all specimens previously referred to T. brevicrista are likely referable to T. plicatus Wood, 1962; (2) statistical analysis supports the separation of T. plicatus from T. corrugatus Wood, 1959, based on its smaller size and less-crenulated cheek teeth, which corroborates their existence at different horizons (T. plicatus earlier Bridgerian [Br2], T. corrugatus late Bridgerian [Br3]); (3) Paramys delicatior Leidy, 1871, is suggested as the senior synonym of T. plicatus Wood, 1962; (4) T. perditus Wood, 1962, is limited to the early Eocene (Washatchian: Wa1-6); and (5) all specimens previously referred to T. nini Wood, 1962, except the holotype, are referred to T. perditus (fide Korth, 1984; contra Anderson, 2015). UUID: http://zoobank.org/59c101e2-cd55-4dce-aeea-3da48c4fbd53


ISSN: 0022-3360
EISSN: 1937-2337
Coden: JPALAZ
Serial Title: Journal of Paleontology
Serial Volume: 94
Serial Issue: 6
Title: The Eocene ischyromyid rodent Thisbemys from the Washakie Formation, Wyoming (early Eocene, late Bridgerian) with comments on the systematics of the genus
Author(s): Korth, William W.
Affiliation: Rochester Institute of Vertebrate Paleontology, Rochester, NY, United States
Pages: 1180-1190
Published: 202011
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 19
Accession Number: 2020-084268
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 5 tables
N41°00'00" - N42°19'60", W110°10'00" - W107°30'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2020
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