Date of Award

January 2017

Document Type


Degree Name

Master of Science (MS)



First Advisor

Joseph H. Hartman


The Judith River Formation has a long history of study, from Meek and Hayden’s expeditions in the 1850s to E. D. Cope’s searches for new dinosaur species. More recently, the Judith River Formation receives a plethora of research in paleontology and geology. Despite this, little work has been done on the freshwater molluscan fauna found within. The purpose of this study was to create a method where accurate species diagnoses become possible, and to create a launching point for future work in the Judith River Formation. Freshwater mollusk specimens were collected from shell beds in the Judith River Formation at the type area in the Missouri River Breaks (Fergus County), and near Rudyard, Montana (Hill County). Specimens were then separated by general morphology and measured for select character traits (e.g. convexity of whorls). Photos of Judith River Formation type specimens were taken at the National Museum of Natural History at the Smithsonian Institution and subsequently measured for the same character traits. A table was created which listed possible character traits for the freshwater mollusk types and each possible outcome was given a code (e.g. 0, 1, 2) for analysis. Then using trait codes assigned to each type species and comparing them to trait codes assigned to collected specimens, species identifications were made. This methodology allows for a more quantitative method of species diagnoses. Accomplishing this is essential to additional cladistical work in the Judith River Formation as better material becomes available. Depositional environment of localities sampled was derived from autecological and lithologic data. This will be beneficial to both paleontologists and geologists for future work in the Judith River Formation