5 The Upper Cretaceous Mancos Group on the Colorado Plateau (Posters)

Monday, 19 May 2025
8:00 AM - 5:30 PM
Ballroom A&B

DISCOVERY, OUTREACH, AND EDUCATION IN THE MANCOS SHALE: SAMPLING CHONDRICHTHYAN TEETH FROM ANT HILLS IN EASTERN UTAH, USA

Paper number: 5-3
Program: Theme Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Vertebrate fossils in the Mancos Shale of eastern Utah are rare, especially when compared to formations such as the Tropic Shale of southern Utah, the Niobrara Chalk of Kansas, or the Pierre Shale of Kansas, Wyoming, and the Dakotas. Ongoing work on revisions to the stratigraphic nomenclature and correlations of units within the Mancos Shale of Utah is motivating renewed research and interest in the fossil assemblages of this region. We examined the chondrichthyan and osteichthyan assemblage of the Ferron – Juana Lopez transition near the border of Carbon and Emery counties in eastern Utah. Previous studies identified 14 fish taxa from this unit, including the teeth of sharks, rays, sawfish, and pycnodonts. For this study, we bulk sampled the debris cones from harvester ant nests that were found to contain shark teeth on initial visual inspection in the field. The sediment was wet screened in the lab and allowed to dry. Volunteers and members of the public with whom we interacted at outreach events were invited to isolate teeth by picking them under binocular microscopes. This engaged hundreds of members of the public and provided the majority of our sample discussed herein. Once the teeth were isolated, they were sorted and identified by two of us as part of the School to Science high school internship program with Science Moab.

Other than abundant specimens of Pycnodontiformes, the rest of the identified teeth are those of members of Elasmobranchii. We found multiple morphotypes of Orectolobiformes. Ptychodus teeth were all fragmentary and consistent with taxa discovered by previous workers, such as P. c.f. mammillaris and P. whipplei. Lamniform taxa discovered thus far include Squalicorax c.f. S. falcatus, Scapanorhynchus, and multiple morphotypes of Cretoxyrhinidae. We identified a few examples each of the batoid taxa Protoplatyrhina and Pseudohyolophus. The sawfish Ptychotrygon c.f. P. triangaularis is particularly abundant and easily recognizable in this assemblage, likely owing to the robust nature of its oral teeth.

Focusing on sampling teeth from ant hills increases the potential sample size compared to traditional surface collection on outcrop. However, it does bias the sample to specimens that are small enough to be carried by the harvester ants. Though this ongoing project will undoubtedly provide a better understanding of the fossil fish assemblage of this portion of the Mancos Shale, it has already accomplished a number a broader impacts. Allowing the public to pick shark teeth at outreach events increases awareness of fossil resources in the area and has the potential to spark interest in science, especially among younger members of the public. This work also provided two of us with our first gateway into rigorous scientific research, presentation, and publishing prior to high school graduation.

Geological Society of America Abstracts with Programs. Vol. 57, No. 5

doi: 10.1130/abs/2025RM-410331

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