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A new species of mosasaur (Squamata, Mosasauridae) from the Pierre Shale (lower Campanian) of Manitoba

Robin Cuthbertson, Jordan C. Mallon, Nicolas E. Campione and Robert B. Holmes
A new species of mosasaur (Squamata, Mosasauridae) from the Pierre Shale (lower Campanian) of Manitoba
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (May 2007) 44 (5): 593-606

Abstract

Plioplatecarpus nichollsae, sp. nov., from the lower Campanian (Pembina Member, Pierre Shale Formation) is diagnosed by the following: a thickened ventral rim of the external naris, a short supratemporal fenestra, a frontal shield with well-developed posterolateral lappets that overlap the parietal dorsally, proximal rib shafts with an approximately circular (but not inflated) cross section, a scapula shaped as in other Plioplatecarpus species but approximately the same size (not larger) than the coracoid, and a moderately large parietal foramen that reaches the frontoparietal suture but does not invade the frontal. The last two characters require that the diagnosis of the genus Plioplatecarpus be emended. With other Plioplatecarpus species, P. nichollsae shares a robust humerus with a distal expansion at least as great as the total length of the bone, a rectangular preorbital frontal shield, a "peg and socket" postorbitofrontal-jugal articulation, a transversely directed ectopterygoid process of the pterygoid, a large, robust quadrate with a distinct eminence on the posterior surface of its shaft, an unossified gap in the ventral wall of the basioccipital, and at least 11 pygal vertebrae. P. nichollsae also shares primitive features with Platecarpus, as well as features apparently intermediate between Platecarpus and Plioplatecarpus. Revision of the genus Platecarpus, currently hypothesized to be both paraphyletic and polyphyletic, as well as a better understanding of the early Campanian mosasaur fauna from the Morden area, are necessary before the phylogenetic significance of some of these characters, and therefore the relationships of Plioplatecarpus nichollsae, can be fully resolved.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 44
Serial Issue: 5
Title: A new species of mosasaur (Squamata, Mosasauridae) from the Pierre Shale (lower Campanian) of Manitoba
Affiliation: Carleton University, Department of Earth Sciences, Ottawa, ON, Canada
Pages: 593-606
Published: 200705
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 36
Accession Number: 2007-111228
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 1 table, sketch map
N49°06'00" - N49°23'60", W98°30'00" - W98°05'60"
Secondary Affiliation: Canadian Museum of Nature, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200722
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