Lives morphologies and body development of Cambrian nemathelminths and arthropods, a testtool for phylogeny analyses and hypotheses

保存完好的各种后生动物早期代表有四个主要来源：下寒武统澄江拉格斯特滕、下寒武统天狼星帕塞特拉格斯特特、中寒武世布尔吉斯页岩拉格斯特滕和下至上寒武统奥斯滕。这些后生动物的化石对我们了解早期后生动物的演化以及后生动物生命开始辐射时所形成的形态和生活方式做出了重大贡献。许多问题都得到了令人满意的解决，但其中一个主要问题仍然存在：节肢动物这一最大的动物分类群系统地属于哪里？哪个是最亲近的亲戚？七年前，长期以来关于与环节动物建立姐妹群关系的教条受到了质疑，并提出了线虫-节肢动物关系的新想法。时至今日，这个问题仍未得到解决。聚焦于上面提到的拉格斯特坦化石中的线虫和节肢动物的代表，我们将调查原始材料，特别强调结构和功能设计以及身体发育。这包括节段进化的重要和最关键的方面，内部连续中胚层细分的外部表达，体部标记化，以及附属物形成，部分特征很可能是线虫中最主要的特征。我们的特别目的是提出从这些活的形态中积累的数据，作为优先方案内不同其他工作组产生的系统发育假说的测试工具。

There are four major sources of exquisitely preserved early representatives of various metazoan taxa: the Lower Cambrian Chengjiang Lagerstätten, the Lower Cambrian Sirius Passet Lagerstätte, the Middle Cambrian Burgess Shale Lagerstätten and the Lower to Upper Cambrian ¿Orsten¿ Lagerstätten. The fossils of these Lagerstätten have contributed significantly to our knowledge of early metazoan evolution and the morphologies and life styles developed at the time, when metazoan life began to radiate. Many questions have become satisfactorily resolved, but one of the major questions remained: Where do the arthropods, the largest animal taxon belong to systematically? Which is the closest relative? Seven years ago, the long-standing dogma of a sister-group relationship with annelids was questioned and the new idea of a nemathelminth-arthropod relationship put forward. Still today, this is not resolved. Focusing on representatives of nemathelminths and arthropods from the fossil lagerstätten mentioned above, we will investigate original material with particular emphasis on structural and functional design and body development. This includes the important and most critical aspects of segment evolution, the external expression of internal serial mesoderm subdivision, body tagmatisation, and appendage formation, features partly most likely primary absent in nemathelminths. Our particular aim is to present the data accumulated from these lived morphologies as a test tool for phylogeny hypotheses resulting from the different other work groups within the Priority Programme.