26-6 Reconstructing the Paleoecology and Community Structure of Late Eocene Insect and Arachnid Faunal Assemblages at Florissant Fossil Beds National Monument, Colorado, USA

Session: Interdisciplinary Paleontology: New approaches to solving complex paleontological problems (Posters)

Poster Booth No.: 34

Presenting Author:

Jesse Easterwood

Authors:

Easterwood, Jesse E.¹, Slattery, Joshua S.², Tenney, Zachary David³

(1) Geology and Geophysics, University of Wyoming, Department of Geology & Geophysics, Laramie, WY, , (2) University of Wyoming, Cheyenne, WY, USA, (3) University of Wyoming, Department of Geology & Geophysics, Laramie, WY, USA,

Abstract:

The Late Eocene of the Rocky Mountains was characterized by greenhouse climatic conditions, elevated global temperatures, and high biodiversity. One of the most significant and fossiliferous Eocene deposits for terrestrial arthropods in North America is the Florissant Formation at Florissant Fossil Beds National Monument in Colorado. Although the insect and arachnid fauna of this formation has been extensively documented taxonomically, comparatively little research has focused on quantitatively reconstructing the assemblage’s paleoecology and community structure.

In this study, we analyze 3,402 insect and arachnid specimens from the Upper Eocene Florissant Formation, drawn from museum collections housed at Florissant Fossil Beds National Monument and supplemented with newly collected material. By assessing taxonomic composition, relative abundance, and ecological guild structure, we evaluate patterns of community organization, trophic representation, and functional diversity within this exceptionally preserved terrestrial arthropod assemblage.

Our results indicate that the fauna is dominated by Coleoptera, Diptera, Hymenoptera, and Hemiptera—clades that structure many modern terrestrial arthropod communities. The Florissant assemblage is thus composed primarily of clades that are especially abundant today in lower-latitude regions characterized by warm, temperate to subtropical climatic regimes comparable to those inferred for central Colorado during the Late Eocene. These findings provide new insights into the ecological organization of Eocene terrestrial ecosystems and establish a quantitative framework for comparing deep-time arthropod communities with modern biodiversity patterns under greenhouse climate conditions.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4, 2026

doi: 10.1130/abs/2026RM-12079

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