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A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia; bridging the Triassic-Jurassic gap

Elizabeth L. Nicholls and Makoto Manabe
A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia; bridging the Triassic-Jurassic gap
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (June 2001) 38 (6): 983-1002

Abstract

Both the genus Shastasaurus and the family Shastasauridae have long been hard to define due to the fragmentary nature of the type specimens. Consequently, recent interpretations of the genus have been based almost entirely on Shastasaurus neoscapularis from the Late Triassic Pardonet Formation of British Columbia. Two new specimens of this taxon, from Pink Mountain, British Columbia, demonstrate that it does not belong in the genus Shastasaurus. This paper describes the new specimens, and refers the species to Metashastasaurus gen nov. Post-cranially, the skeleton of Metashastasaurus resembles that of shastasaurids, differing primarily only in the shape of the scapula and fibula. However, the skull has a unique combination of characters, including large diamond-shaped frontals that enter the supratemporal fenestrae, and very narrow posterior extensions of the nasals, which contact the postfrontals. It also differs from the skull of Shastasaurus in the presence of both a parietal ridge and postparietal shelf. This is a combination of derived characters previously known only in Jurassic forms. The front limb has four proximal carpals and four digits, indicating that previous reconstructions were based on incomplete material. Shastasaurus pacificus Merriam 1895, the type species of the genus Shastasaurus, must be considered a nomen dubium, making the genus Shastasaurus invalid. Until this problem is clarified, the use of the generic name Shastasaurus should be restricted to Merriam's type specimens, of which only Shastasaurus alexandrae and Shastasaurus osmonti are based on adequate material.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 38
Serial Issue: 6
Title: A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia; bridging the Triassic-Jurassic gap
Affiliation: Royal Tyrrell Museum of Palaeontology, Drumheller, AB, Canada
Pages: 983-1002
Published: 200106
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 41
Accession Number: 2001-071920
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. sketch map
N57°00'00" - N58°00'00", W123°00'00" - W122°00'00"
Secondary Affiliation: National Science Museum, JPN, Japan
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200122
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