Date of Award

Spring 12-8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Jaelyn J. Eberle

Second Advisor

David W. Krause

Third Advisor

Donald Lofgren

Fourth Advisor

Christy McCain

Abstract

Strata containing earliest Paleocene (Puercan) vertebrates are important for understanding which lineages survived the Cretaceous-Paleogene (K-Pg) boundary mass extinction and how they diversified afterwards. A new early Puercan mammalian faunal assemblage from the China Butte Member (CBM) of the Fort Union Formation in Wyoming’s Great Divide Basin is only beginning to be described. Here I describe the multituberculates in the assemblage that come from a productive quarry (UCM locality 2011035) that has yielded over 400 vertebrate specimens. UCM locality 2011035 is approximately 46 meters stratigraphically above the contact between the China Butte Member and the underlying Upper Cretaceous (Lancian) Red Rim Member of the Lance Formation. The locality has produced 140 multituberculate fossils, comprised mostly of isolated teeth. I describe a new genus and species of eucosmodontid - Stenocosmodon parvistriatus - as well as Mesodma ambigua, Mesodma thompsoni, Mesodma formosa, Neoplagiaulax macintyrei, Parectypodus vanvaleni and Kimbetohia mziae from UCM locality 2011035. The three dentaries referred to Stenocosmodon preserve a strongly laterally compressed lower incisor and a p4 roughly half the size of known species of Eucosmodon. While similar in size to Stygimys, the p4s of Stenocosmodon have a noticeably higher profile than known species of Stygimys and lack lateral ridges descending both labially and lingually from the serrations. The specimens referred to Kimbetohia mziae preserve the entire lower dentition (i – m2), and are morphologically very similar to ?Kimbetohia mziae from the early Puercan Littleton fauna in Colorado’s Denver Basin. The new material from UCM locality 2011035 helps to solidify that this species is morphologically similar enough to the type species Kimbetohia campi, to be included in the same genus. The locality preserves characteristic Pu1 species: Oxyprimus galadrielae, Conacodon harbourae, Mesodma ambigua, and as well as Parectypodus vanvaleni, which is only known from the Pu2 interval zone and Neoplagiaulax macintyrei, known from Pu2 and Torrejonian-aged localities. This provides strong evidence for UCM locality 2011035 being intermediate between the Pu1 and Pu2 interval zones. The multituberculates from UCM locality 2011035, indicate that early Puercan recovery faunas had greater diversity than initially inferred from other areas in the Western Interior.

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