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The micro from mega: Dental calculus description and the first record of fossilized oral bacteria from an extinct proboscidean

Abstract:

Objective: This study explores the chemical composition and surface aspects of fossilized dental calculus from the South American Quaternary proboscidean Notiomastodon platensis and the first record of fossilized oral bacteria from extinct megafauna. Materials: Blocks of dental calculus removed from the third molar of five specimens of Notiomastodon platensis collected from Brazil, Argentina, and Ecuador. Methods: We analyzed five samples of dental calculus by SEM and SEM-EDS, following a rigid protocol to avoid bacterial contamination. Results: The dental calculus surface is homogeneous, porous, with various crystals, and composed mainly by oxygen and calcium. One sample revealed a well-preserved mineralized biofilm, with several rods and cocci bacteria. Conclusions: This is the first fossilized record of oral bacterial communities associated with extinct proboscideans. Significance: This record confirms the parasitism between oral bacteria and Notiomastodon platensis and will enable the study of paleogenomic aspects of oral microbiota of proboscideans. Limitations: Fossilization conditions of proboscidean teeth with dental calculus are variable among specimens. Although rare, the preservation of oral bacteria is expected because of the oral biofilm composition.