湖北三峡地区埃迪卡拉系灯影组Hiemalora stellaris生物属性及埋藏分析

Hiemalora stellaris是湖北宜昌三峡地区埃迪卡拉系灯影组石板滩生物群中数量最为丰富的化石类型之一,由位于中心位置的圆盘和围绕盘缘向外伸出的似触手状结构组成,似触手状结构长度与圆盘直径具有较好相关性。同时也发现少量Hiemalora与茎干相连,其中一枚产自石板滩段底部的标本保存完整,与茎干连接有叶状体。叶状体呈卵形,可见一级分枝与二级分枝,顶部有呈"牛角状"的尖刺,叶状体形态与Charniodiscus spinosus相似。结合纽芬兰地区发现的Primocandelabrum hiemaloranum,表明Hiemalora作为生物体的固着器官,起到抵御水流冲刷、支撑和固定整个生物体的作用,但与其相连的叶状体表现出不同的形态类型,表明Hiemalora化石可能具有较为多样的生物来源。根据化石的形态特征和埋藏状态分析,Hiemalora在生物生活时位于藻席层之下的沉积物内,常呈正凸起保存于岩层顶面,而茎干和叶状体位于水体中,生物死亡后,叶状体倒伏在藻席层之上,当岩层沿藻席层劈开后,在顶面保存为凹陷的印痕。

HIEMALORA STELLARIS FROM THE EDIACARAN DENGYING FORMATION IN THE YANGTZE GORGES AREA,HUBEI PROVINCE:AFFINITY AND TAPHONOMIC ANALYSIS

Hiemalora stellaris occurs abundantly in the Shibantan biota discovered from the Ediacaran Dengying Formation in the Yangtze Gorges area, Hubei Province. H. stellaris consists of a central disc and surrounding tentacle-like structure, which shows a positive correlation with the diameter of central discs. One specimen, discovered from the bottom of the Shibantan Member of the Dengying Formation, shows that a H. stellaris is attached to a frond-type structure. The ovate frond has a prominent horn-like spiny termination on the top, and shows internal primary and secondary branches, resembling those of Charniodiscus spinosus. The fossil can be compared with Primocandelabrum hiemaloranum that was found in Newfoundland area of Canada, indicating that H. stellaris may represent a holdfast which can be attached to different kinds of fronds. Taphonomic analysis suggests that H. stellaris may live in the sediments below the microbial mats before it is buried and preserved as a mold. Meanwhile, the stem and frond live in water column before they are buried on the surface of the microbial mats and preserved as an impression.