26-2 Tooth Indentations of Microfossils from Micro Vertebrates in the Chadronian and Orellan Periods from the White River Group NE

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

Presenting Author:

Authors:

Abstract:

Micro vertebrates are the most abundant vertebrate members of ecosystems, but are underrepresented in the fossil record. Despite the importance of microvertebrates in ecosystems, ascertaining their predator-prey relationships is difficult since remains are sparse and fragmentary. It is often impossible to taxonomically identify species from microvertebrate remains and determine the anatomical identity of the fossil. This study uses gross description alongside Procrustes analysis of taphonomic landmarks to analyze bite marks on microvertebrate remains from the late Chadronian (~33.8mya) and middle Orellan (~33.4 mya) land mammal ages of Nebraska, USA. We aim to determine the importance of predators and geologic processes in driving microvertebrate fragmentation, as well as identify the predators/scavengers producing bite marks.  

Assemblages were gathered from western harvester ant hills in Nebraska. A subset of 1,066 microfossils was analyzed for breakage patterns; 137 have suspected bite marks, 82 of which had multiple indentations, which could be caused by multiple teeth. The Geomorph package in R was used to record the coordinates and size of each suspected tooth mark and quantify the cusp patterns from the teeth of 12 common potential predators/scavengers from the ecosystems. Indentation patterns were then compared to potential biters using Procrustes analysis with fuzzy matching. Likely predators/scavengers were identified for all 82 specimens with multiple indentations, with Herpetotherium, Copedelphys, and Nanodelphys being the most identified genera. Leptictis, Proterix, Apteronodus, and Proscalops appear to be infrequent predators/scavengers of vertebrates, implying an insectivorous diet. This appears to be a novel and useful method to match indentation marks on the microfossils to candidate predators/scavengers. No major patterns were detected among gross taphonomic characteristics measured from the microfossils.  

The two samples from Nebraska, sourced immediately prior to and after the Eocene-Oligocene Transition (EOT), allow a comparison to be made between ecosystems. Comparing the two time periods on either side of a global climate transition and an understanding of how the transition can provide insight into changes in ecosystem dynamics across the EOT.   

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

doi: 10.1130/abs/2026RM-14168

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