Are palaeoscolecids ancestral ecdysozoans?

The reconstruction of ancestors is a central aim of comparative anatomy and evolutionary developmental biology, not least in attempts to understand the relationship between developmental and organismal evolution. Inferences based on living taxa can and should be tested against the fossil record, which provides an independent and direct view onto historical character combinations. Here, we consider the nature of the last common ancestor of living ecdysozoans through a detailed analysis of palaeoscolecids, an early and extinct group of introvert-bearing worms that have been proposed to be ancestral ecdysozoans. In a review of palaeoscolecid anatomy, including newly resolved details of the internal and external cuticle structure, we identify specific characters shared with various living nematoid and The reconstruction of ancestors is a central aim of comparative anatomy and evolutionary developmental biology, not least in attempts to understand the relationship between developmental and organismal evolution. Inferences based on living taxa can and should be tested against the fossil record, which provides an independent and direct view onto historical character combinations. Here, we consider the nature of the last common ancestor of living ecdysozoans through a detailed analysis of palaeoscolecids, an early and extinct group of introvert-bearing worms that have been proposed to be ancestral ecdysozoans. In a review of palaeoscolecid anatomy, including newly resolved details of the internal and external cuticle structure, we identify specific characters shared with various living nematoid and

祖先重建是比较解剖学（comparative anatomy）与进化发育生物学（evolutionary developmental biology）的核心研究目标之一，在探索发育演化与生物体演化之间的关联时尤为关键。基于现生类群的推断结论，可以且应当通过化石记录进行验证——化石记录为我们提供了独立且直接的历史性状组合视角。本研究通过对古蠕虫类（palaeoscolecids）的详细分析，探讨现生蜕皮动物（ecdysozoans）的最后共同祖先的本质；古蠕虫类是一类已灭绝的早期具翻吻蠕虫类群，曾被提出为蜕皮动物的祖先类群。在对古蠕虫类解剖结构的综述研究中，我们纳入了新解析得到的内外角质层结构细节，并识别出与多种现生线虫类（nematoid）共有的特定性状