Date of Award

Spring 1-1-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Jaelyn J. Eberle

Second Advisor

Christy M. McCain

Third Advisor

Benjamin J. Burger

Fourth Advisor

Leilani Arthurs

Abstract

An earliest Paleocene (Puercan) locality discovered by James and Jeannine Honey in the lower China Butte Member of the Fort Union Formation in Wyoming’s Great Divide Basin (GDB) contains a diverse mammalian faunal assemblage, including a number of ‘condylarth’ taxa. Previous studies have suggested that this faunal assemblage may be correlative with the early Puercan (Pu1) Littleton fauna in the Denver Basin, due to multiple shared taxa. From the University of Colorado Museum of Natural History (UCM) locality 2011035, I describe three new periptychid ‘condylarths’, in addition to the first occurrences of Maiorana noctiluca,Ampliconus antoni, and Conacodon harbourae from the GDB. The first new genus and species, Beornus honeyi, is based on a left dentary containing p3–m3. B. honeyi is 10–12% larger than Conacodon delphae (the largest documented species of Conacodon) and is similar in morphology to Auraria urbana, but differs in its relatively smaller molar paraconid, absence of a lingual cingulid, and more posteriorly-projecting m3 hypoconulid. A new species of Conacodon, C. hettingeri, is based on left and right dentaries containing Lp3–m3 and Rp4–m3, respectively. C. hettingeri is close in molar morphology to species of Conacodon, differing in its larger size and relatively less posteriorly-projecting m3 hypoconulid. Finally, the third new genus and species of periptychid from the GDB, Miniconus jeanninae, is based on two right dentaries containing p4–m3 and p3–m3, as well as a left dentary containing p4–m2. This new taxon is close in morphology to Oxyacodon archibaldi, sharing a distinct paraconulid, but differs primarily in the more anterior placement of the entoconid. Based on its morphological similarity to M. jeanninae and its differences from other species of Oxyacodon, O. archibaldi is placed here within the new genus Miniconus. To examine the relationships of the three new GDB taxa to each other and to other Puercan periptychidss from the Western Interior of North America, a phylogenetic analysis was performed using 26 Puercan ‘condylarth’ taxa and 58 dental characters. Characters were aggregated from previous phylogenetic analyses of ‘condylarth’ taxa and scored based on comparative study with specimens from several museum collections as well as descriptions from the literature. The resulting strict consensus tree of 216 steps indicates that the three new periptychid species from the GDB are nested within Periptychidae. B. honeyi is closely related to A. urbana from the Denver Basin, whereas C. hettingeri belongs within the genus Conacodon, and M. jeanninae forms a clade with Miniconus archibaldi. The new genus Miniconus appears to be monophyletic, whereas the genus Conacodon is paraphyletic in my analysis. Additionally, the primitive, early Puercan ‘condylarth’ taxa Mimatuta spp. and Maiorana noctiluca fall within Periptychidae, supporting the traditional placement of these taxa within that family. C. harbourae, A. antoni, and M. noctiluca, which I report from the GDB, have been previously described elsewhere. The presence of C. harbourae in both the GDB and the Denver Basin suggests that the Littleton fauna is correlative with UCM locality 2011035. Also, the presence of C. harbourae, A. antoni, and M. noctiluca in Wyoming’s Hanna Basin confirms the hypothesis that the Great Divide and Hanna Basins were contiguous at the start of the Paleocene. Finally, the occurrence of the three new periptychid taxa in the GDB suggests that mammalian diversity is higher than previously thought for the early Puercan.

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Paleontology Commons

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