通过使用以前未探索过的技术（例如，X射线显微断层扫描、扫描和透射电子显微镜以及能量色散光谱元素映射）检查更多的标本，研究人员发现证据表明，云南虫类鳃弓由细胞软骨和以微纤维为主的细胞外基质组成，这是迄今为止被认为是脊椎动物特有的特征。系统发育分析进一步支持云南虫类是干脊椎动物。
据介绍，咽弓是一项关键革新，可能有助于脊椎动物的颌骨和脑壳的进化。长期以来，人们一直假设咽部（分支）弓是从脊椎动物祖先（例如非脊椎动物的脊索文昌鱼中的软骨棒）进化而来的，但这种祖先的解剖结构是否存在仍然是未知的。被称为云南虫类的有争议的寒武纪动物的咽部骨骼，可能包含限制拱门早期进化的最古老的化石证据，但它与脊椎动物的相关性仍然存在争议。
附：英文原文
Title: Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans
Author: Qingyi Tian, Fangchen Zhao, Han Zeng, Maoyan Zhu, Baoyu Jiang
Issue&Volume: 2022-07-08
Abstract: Pharyngeal arches are a key innovation that likely contributed to the evolution of the jaws and braincase of vertebrates. It has long been hypothesized that the pharyngeal (branchial) arch evolved from an unjointed cartilaginous rod in vertebrate ancestors such as that in the nonvertebrate chordate amphioxus, but whether such ancestral anatomy existed remains unknown. The pharyngeal skeleton of controversial Cambrian animals called yunnanozoans may contain the oldest fossil evidence constraining the early evolution of the arches, yet its correlation with that of vertebrates is still disputed. By examining additional specimens in previously unexplored techniques (for example, x-ray microtomography, scanning and transmission electron microscopy, and energy dispersive spectrometry element mapping), we found evidence that yunnanozoan branchial arches consist of cellular cartilage with an extracellular matrix dominated by microfibrils, a feature hitherto considered specific to vertebrates. Our phylogenetic analysis provides further support that yunnanozoans are stem vertebrates.
DOI: abm2708
Source: https://www.science.org/doi/10.1126/science.abm2708