189-26 Under the Brush: A Preparation Case Study on a Rhinocerotid Cranium from the John Day Formation (Crook County, Oregon, USA)

Session: Paleontology, Paleoecology/Taphonomy (Posters)

Presenting Author:

Authors:

Abstract:

    A rhinocerotid specimen was excavated from an outcrop of the Turtle Cove member of the John Day Formation in July 2018. The specimen, consisting of a near complete cranium and mandible, was found in situ thoroughly penetrated and entangled with sagebrush roots. The specimen was successfully extracted and brought to the University of Oregon for preparation with the roots still attached to and within the specimen. Several years later, the specimen was prepared, identified, and catalogued into the Condon Fossil Collection of the University of Oregon Museum of Natural and Cultural History (UOMNCH). The presence of the interwoven roots created significant challenges; the roots passed directly through the numerous fractures in the cranium and mandible, and many of them surrounded and obscured the teeth of the specimen. The specimen was so thoroughly enmeshed with roots that removing them risked catastrophic breakage. This, combined with the brittle, crumbly claystone matrix surrounding the cranium, slowed the task of preparation and consolidation. Individual preparation problems required specific tools and techniques for matrix removal.  

     A pneumatic air scribe was used to dislodge matrix from the specimen’s surface, thin roots were gently pulled away by hand, and thicker branches were clipped as close to the fossil surface as possible with small pruning shears. Because unavoidable new fractures developed when the specimen was removed from its initial plaster jacket from the field, a permanent clamshell-style storage cradle was crafted to allow examination of both sides of the delicate specimen. With preparation complete, the specimen was identified as Diceratherium based on the characters of its molarized premolars and the distinct paired flanges on the tips of its nasals. The specimen’s cranium is nearly complete, although it lacks basioccipital bones. The specimen demonstrates the importance of applying best practices for preparation in order to retain the data required for scientific study of fragile vertebrate fossil remains.  

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

doi: 10.1130/abs/2025AM-9311

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