The Eucraniini are a small dung beetle tribe endemic to Argentina (4 genera with 14 species), adapted to live in extremely arid environments, usually feeding on dry, small mammal dung pellets. These beetles grasp the dried pellets lifting them by the foretibiae and run forward on the middle and hindlegs. Here, the eucraniine mouthparts (epipharynx, labium, mandibles and maxillae) and ventral part of the clypeus were examined. According to the results, the structures were collectively defined as MOS (i.e., mouthpart structures), which is related to the unique feeding behavior displayed by these dung beetles (i.e., the food-lifting). The modification patterns of the MOS were examined in the lifters Eucraniini and compared to those of Neotropical tunneler species of Phanaeini and Dichotomiini, but also to the Afrotropical genus Pachysoma, with which they share many characters. Well-differentiated and distinguished MOS were detected in the three Neotropical tribes Eucraniini, Phanaeini, and Dichotomiini, evidencing also how the variation patterns of this complex system mirror the phylogenetic relationships among these tribes, and also within the Eucraniini genera.

中文翻译：

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Eucraniini（鞘翅目，金龟科）口器结构的进化

Eucraniini 是阿根廷特有的小型蜣螂部落（4 属 14 种），适应生活在极其干旱的环境中，通常以干燥的小型哺乳动物粪便为食。这些甲虫通过前肢抓住干燥的颗粒，并在中间和后腿上向前奔跑。在这里，检查了 eucraniine 口器（上颌、下唇、下颌和上颌）和唇部的腹侧部分。根据结果​​，这些结构被统称为MOS（即口器结构），这与这些蜣螂所表现出的独特摄食行为（即食物提升）有关。MOS 的修改模式在 Eucraniini 的升降机中进行了检查，并与 Phanaeini 和 Dichotomiini 的新热带隧道机物种的修改模式进行了比较，但也与 Afrotropical Pachysoma 属的修改模式进行了比较，与他们共享许多字符。在三个新热带部落 Eucraniini、Phanaeini 和 Dichotomiini 中检测到了分化良好的 MOS，这也证明了这个复杂系统的变异模式如何反映了这些部落之间以及 Eucraniini 属内的系统发育关系。