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.

中文翻译：

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来自巨型的微观：牙结石的描述和来自已灭绝长鼻动物的口腔细菌化石的首次记录

客观的

本研究探索了来自南美第四纪长鼻类Notiomastodon platensis 的牙结石化石的化学成分和表面方面，以及来自已灭绝巨型动物的口腔细菌化石的第一个记录。

材料

从巴西、阿根廷和厄瓜多尔收集的五个Notiomastodon platensis标本的第三磨牙中取出的牙结石块。

方法

我们遵循严格的方案，通过 SEM 和 SEM-EDS 分析了五个牙结石样本，以避免细菌污染。

结果

牙结石表面均质、多孔，有多种晶体，主要由氧和钙组成。一个样本显示了一个保存完好的矿化生物膜，带有几个杆状菌和球菌。

结论

这是与已灭绝的长鼻目相关的口腔细菌群落的第一个化石记录。

意义

该记录证实了口腔细菌和钝乳齿象之间的寄生关系，并将有助于研究长鼻类口腔微生物群的古基因组学方面。

限制

具有牙结石的长鼻类牙齿的化石条件因标本而异。虽然很少见，但由于口腔生物膜的组成，口腔细菌的保存是值得期待的。