Giribet Gonzalo, Edgecombe Gregory D
Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK.
Integr Comp Biol. 2017 Sep 1;57(3):455-466. doi: 10.1093/icb/icx072.
Twenty years after its proposal, the monophyly of molting protostomes-Ecdysozoa-is a well-corroborated hypothesis, but the interrelationships of its major subclades are more ambiguous than is commonly appreciated. Morphological and molecular support for arthropods, onychophorans and tardigrades as a clade (Panarthropoda) continues to be challenged by a grouping of tardigrades with Nematoida in some molecular analyses, although onychophorans are consistently recovered as the sister group of arthropods. The status of Cycloneuralia and Scalidophora, each proposed by morphologists in the 1990s and widely employed in textbooks, is in flux: Cycloneuralia is typically non-monophyletic in molecular analyses, and Scalidophora is either contradicted or incompletely tested because of limited genomic and transcriptomic data for Loricifera, Kinorhyncha, and Priapulida. However, novel genomic data across Ecdysozoa should soon be available to tackle these difficult phylogenetic questions. The Cambrian fossil record indicates crown-group members of various ecdysozoan phyla as well as stem-group taxa that assist with reconstructing the most recent common ancestor of panarthropods and cycloneuralians.
蜕皮原口动物（蜕皮动物总门）的单系性在其被提出20年后，已是一个得到充分证实的假说，但其主要亚支的相互关系却比通常认为的更为模糊。节肢动物、有爪动物和缓步动物作为一个进化枝（泛节肢动物）的形态学和分子学证据，在一些分子分析中，因缓步动物与线虫类归为一组而继续受到挑战，尽管有爪动物一直被认为是节肢动物的姊妹群。1990年代由形态学家提出并在教科书中广泛使用的环神经动物和有颚动物的分类地位尚不稳定：在分子分析中，环神经动物通常不是单系的，而由于铠甲动物门、动吻动物门和鳃曳动物门的基因组和转录组数据有限，有颚动物要么被反驳，要么未得到充分检验。然而，很快就会有全新的蜕皮动物总门基因组数据来解决这些棘手系统发育问题。寒武纪化石记录显示了各种蜕皮动物门的冠群成员以及有助于重建泛节肢动物和环神经动物最近共同祖先的干群分类单元。
