Gill rays of primitive vertebrate Yunnanozoon from Early Cambrian: a first record

Yunnanozoans(including Yunnanozoon and Haikouella)are important representatives of the primitive vertebrates in the Early Cambrian Chengjiang fauna.For Yunnanozoans,we know less about Yunnanozoon than about Haikouella due to the poor preservation of Yunnanozoon.Up to now,there have been some reports that Haikouella had developed gill rays,while there have been no reports on Yunnanozoon.In this paper,we described our new findings of the distinct gill rays of Yunnanozoon lividum based on new well-preserved material collected from the Lower Cambrian Maotianshan Shale in Xiaolantian of Yunnan Province,China.This study provides new data on the evolutionary relationship of the primitive vertebrates and their early evolution.