37-8 Campanian Marine Vertebrate Fossils from the Hatch Mesa Sandstone, Eastern Utah

Session: Geoscience Research Poster Showcase by 2YC and 4YCU Undergraduate Students

Poster Booth No.: 131

Presenting Author:

Jay Salmi

Authors:

Salmi, Jay¹, Anderson, Evan², Sonheim, Ryan Jacob³, King, Michael Ryan⁴, Lively, Joshua Ryan⁵, Kirkland, James I.⁶

(1) Natural & Environmental Sciences, Western Colorado University, Gunnison, CO, USA, (2) Natural & Environmental Sciences, Western Colorado University, Gunnison, CO, USA, (3) Natural & Environmental Sciences, Western Colorado University, Gunnison, CO, USA, (4) Natural & Environmental Sciences, Western Colorado University, Gunnison, CO, , (5) Natural & Environmental Sciences, USU Eastern Prehistoric Museum, Price, UT, USA, (6) Utah Geological Survey, Salt Lake City, UT, ,

Abstract:

This study presents the first known report of a vertebrate fossil assemblage from the Campanian Hatch Mesa Sandstone near Green River, Utah. The fossils occur within localized, channelized, coarse-grained sandstone bodies of the Upper Cretaceous Mancos Shale. These sandstone bodies are interpreted as offshore marine channels that accumulated sediment coarser than the surrounding marine mudstones.

Seventeen undergraduate students participated in systematic surface collection through a cooperative effort involving a university, museum repository, and government agency. Three students volunteered to serve as field managers. With guidance from the instructor, these students reviewed scientific literature and satellite imagery to develop a strategy for surveying and surface collecting fossils from the localized sandstone bodies within a limited field period. They also developed a standardized specimen-numbering and documentation system for cohesive collection methods. All students worked in close proximity and remained under the direct oversight of the instructor throughout the field activity. Each student field manager assisted approximately one-third of the class by helping manage the sheer volume of surface-collected material and ensuring that each specimen was described on a specimen card and assigned a consistent field number.

Following collection, the student field managers developed a preliminary classification system based on specimen color, length, symmetry, serrations, striations, curvature, and surface texture. Of the sixty-four fossils with definable morphology, shark teeth dominate the surface-collected assemblage. Scapanorhynchus is the most abundant identified taxon, whereas teeth attributed to Squalicorax and Cretalamna are less common. Batoids are represented by a Texatrygon tooth and a Ptychotrygon dermal denticle. One possible hybodontiform tooth was also recovered. These preliminary findings document a diverse Campanian marine chondrichthyan assemblage and demonstrate how structured student field leadership can facilitate the surface collection and documentation of large quantities of fossil material within a short field period while contributing to original paleontological research.

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