70-4 New Fossils from the Eocene Kishenehn Biota, Northwestern Montana: Implications for Trans-Beringian Dispersal

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns (Posters)

Poster Booth No.: 174

Presenting Author:

Kevin Mulcahy

Authors:

Mulcahy, Kevin Daniel¹, Constenius, Kurt², Greenwalt, Dale³, Rhinehart, Parker⁴, Thompson, Lauren K.⁵, Beard, K. Christopher⁶

(1) Biodiversity Institute & Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA, (2) Department of Geosciences, University of Arizona, Tucson, AZ, USA, (3) Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA, (4) Biodiversity Institute & Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA, (5) Biodiversity Institute & Department of Ecology and Evolutionary Biology, Lawrence, KS, USA, (6) Biodiversity Institute & Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA,

Abstract:

The Kishenehn Formation is a Paleogene (Eocene and Oligocene) unit which outcrops through northern Montana and southern British Columbia, hundreds of miles north of other, better-studied contemporary localities. It is paleontologically significant, as it preserves fossils from a high relief paleoenvironment located in northwestern North America, offering a unique perspective in trans-Beringian paleontology. Since early work in the 1950s, a rich collection of fossils has been recovered from the Kishenehn, including diverse assemblages of fish and plants, and an important invertebrate Lagerstätte.

The renowned paleomammalogist, Mary R. Dawson made especially significant contributions to the study of Kishenehn paleontology. Her decades-long collaboration with Kurt Constenius culminated in a 2018 monograph documenting a rich assemblage of the formation’s Uintan-aged (Middle Eocene, ~45 Ma) mammals, which bore striking similarities to Asian faunas. However, many of these specimens were fragmentary and could not be confidently assigned to any known taxon, leading Dawson and Constenius to emphasize the need for continued collection.

Here, we present the newest additions to the fauna from the Kishenehn Formation of northwestern Montana. These specimens were all collected following the publication of the Dawson and Constenius monograph, and they add significantly to our understanding of Eocene biota from this region. Among these fossils, KUVP 158337 is particularly notable as it represents the northernmost record of Dinocerata (uintatheres).  This group of large herbivorous mammals is known from a disjunct distribution consisting of central North America and Asia, and the Kishenehn specimen provides additional support for a trans-Beringian dispersal route.

These new finds build upon Dawson’s foundational work and add significantly to our understanding of Kishenehn paleontology. Continued collection will yield invaluable insights into the evolution of vertebrate and invertebrate communities in comparatively high latitudes and in montane environments, as well as the iterative patterns of trans-Beringian dispersal by mammals and other animals during the Paleogene.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11394

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.