The ecdysozoans are the most diverse animal group on Earth^{1, 2}. Molecular clock studies indicate that the ecdysozoans may have diverged and diversified in the Ediacaran Period^{3, 4}, but unambiguous ecdysozoan fossils first appear in the earliest Cambrian and are limited to cycloneuralians^5–7. Here we report new material of the early Cambrian microscopic animal Saccorhytus coronarius, which was previously interpreted as a deuterostome⁸. Saccorhytus coronarius is reconstructed as a millimetric and ellipsoidal meiobenthic animal with a spinose armor and an anterior mouth but no anus. Purported pharyngeal gills in support of the deuterostome hypothesis⁸ are shown to be taphonomic artifacts. Phylogenetic analyses indicate that Saccorhytus coronarius belongs to the total-group Ecdysozoa, highlighting the morphological and ecological diversity of early Cambrian ecdysozoans.

中文翻译：

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一种早期寒武纪蜕皮动物，有终末嘴但没有肛门

蜕皮动物是地球上最多样化的动物群^{1, 2}。分子钟研究表明，蜕皮动物可能在埃迪卡拉纪发生分化和多样化^{3, 4}，但明确的蜕皮动物化石首先出现在最早的寒武纪，仅限于气旋动物^5-7。在这里，我们报告了早期寒武纪显微动物Saccorhytus coronarius 的新材料，它以前被解释为 deuterostome ⁸。Saccorhytus coronarius被重建为具有棘甲和前嘴但没有肛门的毫米和椭圆形小底栖动物。据称咽鳃支持后口假设⁸被证明是埋音学的人工制品。系统发育分析表明Saccorhytus coronarius属于全群蜕皮动物，突出了早期寒武纪蜕皮动物的形态和生态多样性。