Lower Eocene (Wasatchian-aged) sediments of the Margaret Formation on Ellesmere Island in Canada's High Arctic preserve evidence of a rainforest inhabited by alligators, turtles, and a diverse mammalian fauna. The mammalian fossils are fragmentary and often poorly preserved. Here, we offer an alternative method for their identification. Among the best preserved and extensive of the Eocene Arctic forests is the Strathcona Fiord Fossil Forest, which contains permineralized in situ tree stumps protruding from a prominent coal seam, but a paucity of vertebrate fossils. In 2010 and 2018, we recovered mammalian tooth fragments at the fossil forest, but they are so incomplete as to be undiagnostic by using their external morphology. We used a combination of light microscopy and SEM analysis to study the enamel microstructure of two tooth fragments from the fossil forest-NUFV2092B and 2092E. The results of our analysis indicate that NUFV2092B and 2092E have Coryphodon-enamel, which is characterized by vertical bodies that manifest as bands of nested chevrons or treelike structures visible in the tangential section under light microscopy. This enamel type is not found in other mammals known from the Arctic. Additionally, when studied under SEM, the enamel of NUFV2092B and 2092E has rounded prisms that open to one side and are surrounded by interprismatic matrix that is nearly parallel to the prisms, which also occurs in Coryphodon enamel, based on prior studies. The tooth fragments reported here, along with some poorly preserved bone fragments, thus far are the only documented vertebrate fossils from the Strathcona Fiord Fossil Forest. However, fossils of Coryphodon occur elsewhere in the Margaret Formation, so its presence at the fossil forest is not surprising. What is novel in our study is the way in which we identified the fossils using their enamel microstructure.

中文翻译：

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利用牙釉质微结构识别始新世北极森林中的哺乳动物化石。

加拿大高北极地区Ellesmere岛玛格丽特组的始新世（Wasatchian时代）沉积物保留了鳄鱼，海龟和各种哺乳动物组成的热带雨林的证据。哺乳动物化石是零碎的，而且往往保存不善。在这里，我们提供了另一种识别方法。在始新世北极森林中，保存最完好的和广泛的是斯特拉斯科纳峡湾化石森林，其中包含从突出的煤层中伸出的矿化的原位树桩，但缺乏脊椎动物化石。在2010年和2018年，我们在化石森林中恢复了哺乳动物的牙齿碎片，但它们不完整，无法通过使用其外部形态进行诊断。我们使用光学显微镜和SEM分析的组合来研究化石森林-NUFV2092B和2092E中两个牙齿碎片的牙釉质显微结构。我们的分析结果表明，NUFV2092B和2092E具有冠状牙釉质，其特征是垂直体显示为切面可见的嵌套人字形或树状结构带，在光学显微镜下可见。在北极已知的其他哺乳动物中未发现这种搪瓷类型。此外，在SEM下进行研究时，NUFV2092B和2092E的搪瓷具有向一侧开口的圆形棱柱，并被几乎平行于该棱柱的棱晶基质所围绕，根据先前的研究，在Coryphodon搪瓷中也存在这种现象。此处报告的牙齿碎片以及一些保存不佳的骨骼碎片，迄今为止，斯特拉斯科纳峡湾化石森林中仅有的文献记载有脊椎动物化石。但是，珊瑚状化石出现在玛格丽特组的其他地方，因此它在化石森林中的存在不足为奇。在我们的研究中，新颖的是我们利用搪瓷显微结构鉴定化石的方式。