Systematics of the soft-shelled turtles (Family Trionychidae) from the Judith River Formation (Campanian)
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1992
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Abstract
Many of the osteological features historically considered taxonomically and/or phylogenetically valuable for trionychids vary within, and/or continuously among, extant species. Thus, trionychid species are most reliably identified using suites of features and allowing for potentially extensive intraspecific variation. Only four of the fifteen recognized species of trionychids from the Judith River Formation (Campanian) are present in the unit. Based on diagnostic shell features, the traditional referral of these four species to Aspideretes is inappropriate. Instead, they represent two new genera: Aspideretoides gen. nov. (3 species) and Apalonoides gen. nov. (1 species). The taxonomic diversity of Judith River trionychids compares to that of extant assemblages, but it is less than that of younger North American fossil assemblages. This suggests that the apparent radiation(s) of North American fossil trionychids occurred after the Campanian and/or in an area other than that preserved as the Judith River Formation.
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Bibliography: p. 442-482.
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Citation
Gardner, J. D. (1992). Systematics of the soft-shelled turtles (Family Trionychidae) from the Judith River Formation (Campanian) (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/14763