The vertebrate fauna of the Late Cretaceous Mussentuchit Member of the Cedar Mountain Formation has been studied for nearly three decades, yet the fossil-rich unit continues to produce new information about life in western North America approximately 97 million years ago. Here we report on the composition of the Cliffs of Insanity (COI) microvertebrate locality, a newly sampled site containing perhaps one of the densest concentrations of microvertebrate fossils yet discovered in the Mussentuchit Member. The COI locality preserves osteichthyan, lissamphibian, testudinatan, mesoeucrocodylian, dinosaurian, metatherian, and trace fossil remains and is among the most taxonomically rich microvertebrate localities in the Mussentuchit Member. To better refine taxonomic identifications of isolated theropod dinosaur teeth, we used quantitative analyses of taxonomically comprehensive databases of theropod tooth measurements, adding new data on theropod tooth morphodiversity in this poorly understood interval. We further provide the first descriptions of tyrannosauroid premaxillary teeth and document the earliest North American record of adocid remains, extending the appearance of this ancestrally Asian clade by 5 million years in western North America and supporting studies of pre-Cenomaninan Laurasian faunal exchange across Beringia. The overabundance of mesoeucrocodylian remains at the COI locality produces a comparatively low measure of relative biodiversity when compared to othermicrovertebrate sites in the MussentuchitMember using both raw and subsampling methods. Much more microvertebrate research is necessary to understand the roles of changing ecology and taphonomy that may be linked to transgression of the Western Interior Seaway or microhabitat variation.
Bibliographical noteFunding Information:
Haviv Avrahami was supported by an Undergraduate Research Assistantship from the Appalachian State University Office of Student Research. The screen washing station was constructed with Appalachian State University Research Council Funding to Andrew B. Heckert. Funding from The Canyonlands Natural History Association and permits from The Bureau of Land Management and the Utah Geological Survey enabled this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Copyright © 2018 Avrahami et al.
- Cedar mountain formation
- Mussentuchit member
- Upper cretaceous