Biostratigraphic Revision of <i>Esthonyx</i> (Tillidontia, Mammalia) in the Contect of Climate Change in the Lower Eocene of the Bighorn Basin, Wyoming
- Authors
- Publication Date
- Jul 01, 2024
- Source
- University of Nebraska - Lincoln
- Keywords
- License
- Unknown
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Abstract
Esthonyx is an early Eocene tillodont found in North America, Europe, and India. The genus was named by Edward Drinker (E. D.) Cope in 1874 based on specimens from the San Jose Formation in New Mexico. Since then, several species of Esthonyx have been described from North America alone. The best record of Esthonyx comes from the central Bighorn Basin (BHB) in Wyoming, where it appears in 220 localities in a 640 m-thick stratigraphic succession. Since the last summary of Esthonyx in the BHB, several hundred new specimens have been collected and curated at the Denver Museum of Nature and Science and the Smithsonian National Museum of Natural History. Herein, I revise the taxonomy and stratigraphic distribution of Esthonyx in the central BHB. I also compare taxonomy and body mass changes with the paleoclimate record, including two hyperthermals recently identified in the study area. I identify three species of Esthonyx in the Wasatchian sequence: E. spatularius Cope, 1880, E. bisulcatus Cope, 1874, and E. acutidens Cope, 1881, using previous diagnoses, novel character combinations, and character quantifications. Additional undescribed species of Esthonyx may be present in the study area. My results slightly extend the stratigraphic ranges of the three species described by previous studies, but they also reveal a strong correlation between smaller body size in E. bisulcatus and the ETM2 and H2 hyperthermals. Advisor: Ross Secord
