The placozoan Trichoplax adhaerens is a tiny hairy plate and more simply organized than any other living metazoan. After its original description by F.E. Schulze in 1883, it attracted attention as a potential model for the ancestral state of metazoan organization, the “Urmetazoon”. Trichoplax lacks any kind of symmetry, organs, nerve cells, muscle cells, basal lamina, and extracellular matrix. Furthermore, the placozoan genome is the smallest (not secondarily reduced) genome of all metazoan genomes. It harbors a remarkably rich diversity of genes and has been considered the best living surrogate for a metazoan ancestor genome. The phylum Placozoa presently harbors three formally described species, while several dozen “cryptic” species are yet awaiting their description. The phylogenetic position of placozoans has recently become a contested arena for modern phylogenetic analyses and view-driven claims. Trichoplax offers unique prospects for understanding the minimal requirements of metazoan animal organization and their corresponding malfunctions.

中文翻译：

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神秘的 Placozoa 第 1 部分：探索进化论争议和贫乏的生态知识

placozoan Trichoplax adhaerens是一个毛茸茸的小盘子，比任何其他活着的后生动物组织起来都更简单。在 1883 年由 FE Schulze 最初描述后，它作为后生动物组织祖先状态“Urmetazoon”的潜在模型引起了人们的注意。螺旋藻缺乏任何对称性、器官、神经细胞、肌肉细胞、基底层和细胞外基质。此外，平台动物基因组是所有后生动物基因组中最小的（不是二次减少的）基因组。它拥有极其丰富的基因多样性，被认为是后生动物祖先基因组的最佳活替代品。Placozoa 门目前拥有三个正式描述的物种，而几十个“神秘”物种正在等待它们的描述。扁盘动物的系统发育位置最近已成为现代系统发育分析和观点驱动主张的一个有争议的领域。Trichoplax为了解后生动物组织的最低要求及其相应的故障提供了独特的前景。