高家山生物群中的非矿化微生物假形化石:埃迪卡拉纪末期生物软躯体保存方式的新认识

Non-mineralized microbial pseudofossils in Gaojiashan biota:A new understanding of the preservation of organisms soft bodies in the latest Ediacaran

陕西南部宁强地区的李家沟剖面灯影组高家山生物群产有大量磷酸盐化实体化石,包括各类管状化石、瓶状化石、疑难化石以及钙化蓝细菌等,类型丰富。近年来,随着研究的深入,微生物假形化石在该生物群中也被不断发现。由于微生物假形化石是生物死亡后腐解埋藏过程中生物体被微生物(球状和丝状蓝细菌)直接取代,因而原始生物体的结构形态得以完好保存。微生物可以通过改变环境中的物理化学条件使磷酸盐富集和快速堆积,对生物的非矿物组织包括软躯体的保存起到了很重要的作用。根据替代程度不同可以划分为完全替代类型和未完全替代类型。这一发现提供了高家山生物群中生物非矿化组织的另一种保存方式。微生物通过铸型完整复制了生物软躯体以及可能的胚胎形态特征,提供了对此时期软躯体保存的新认识。

The Ediacaran Gaojiashan biota from the Dengying Formation in Lijiagou section in the southern Shaanxi Province contains a large number of phosphatized fossils,including abundant tubular fossils,vase-shaped fossils and calcified cyanobacteria.With the deepening of research,microbial pseudofossils are recovered in the biota.The structure and even the whole body were duplicated by aggregated spherical or filamentous cyanobacteria through direct replacement of microorganisms.Microorganisms can enrich and accumulate phosphate rapidly by changing the physical and chemical conditions in the environment,which plays an important role in the preservation of non-mineral tissues including soft bodies of organisms.According to the degree of substitution,they can be divided into complete substituting and incomplete substituting types.Soft bodies or possible embryonic morphological characteristics were completely duplicated by microorganisms through casting moulds.This discovery provides another way for the preservation of non-mineralized biological tissues in Gaojiashan biota and a new understanding of the preservation of organisms soft bodies in this period.