23-11 Capturing variation in the Schreger Pattern in the tusk of a Columbian Mammoth (Mammuthus columbi) from southern California, USA

Session: Paleontology of North America (Posters)

Presenting Author:

Authors:

Abstract:

The Schreger pattern is a structural feature unique to proboscidean tusk dentin that reflects the intersection of dentinal tubules during dentin deposition. Previous studies used this angle of intersecting lines to distinguish between proboscidean taxa (e.g., Mammuthus v. Mammut). Schreger angles overlap among genera, and vary according to their location on the tusk. In this study, we seek to capture the full range of variation in Schreger angles within a single Mammuthus columbi tusk. To accomplish this goal, samples of dentin were collected from six locations along tusk length and at multiple locations along tusk width for each location. Multiple Schreger angles were measured on photographs of fresh dentin surfaces in transverse view for each sample using ImageJ, as following traditional methods of measuring on thin sections or polished surfaces obscured the feature entirely. 

Preliminary results show Schreger angles ranging from 39-93°, with a mean of 57° and a standard deviation of 10.8. Schreger angles near the cementum-dentin junction (M = 71°) are, on average, greater than those in the tusk interior (64°). Angles show an overall increase from the tip (M = 57°) to the middle portion of the tusk (M = 67°). A cross-comparison to the tusk of Mammut pacificus (Pacific mastodon) fails to replicate the results of previous analyses showing differences by genus; Mammut pacificus showed mammoth-like ranges between 99-64°. The variation of Schreger angles within a single tusk and within genera suggests there is a limit to the diagnostic power of Schreger angles of proboscideans.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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