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对澄江化石库中Ｙｕｎｎａｎｏｚｏｏｎ（云南虫）重新研究表明，其身体由吻、领和躯干三部分构成；躯干前段为具有成对鳃孔的咽腔，后段为消化区。这种独特的身体造型与现生肠鳃类半索动物几无二致，从而表明这个早寒武世动物是地球上半索动物门中已知最古老的祖先类型。
A re-study of Yunnanozoon (Yunnan bug) in the Chengjiang fossil store shows that its body consists of three parts: kiss, collar and trunk; the anterior segment of the trunk is the pharynx with paired gill openings and the posterior segment is the digestive tract. This unique form of body resembles an existent gill-half animal, indicating that this pre-Cambrian animal is the oldest ancestral type known to be found on the upper part of the globe.