Ediacaran microbial colonies
Ediacaran microbial colonies
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DOI：
10.1111/j.1502-3931.2007.00025.x
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发表时间：
2007-09-01
期刊：
影响因子：
1.5
通讯作者：
Gerdes, Gisela
中科院分区：
文献类型：
--
作者：
Grazhdankin, Dmitriy;Gerdes, Gisela
神秘的盘状化石在新元古代沉积序列中很常见，并且在地层记录中早于多种埃迪卡拉化石组合的首次出现。这些新元古代盘状化石被称为“水母”，通常被解释为腔肠动物级生物，这意味着真后生动物祖先的身体结构呈放射状对称。然而，对白海地区保存完好的盘状化石的分析表明，大多数盘状化石代表了殖民微生物。例如，局部黄铁矿化揭示了埃迪卡里亚存在明显的丝状亚结构，而环水母和帕利拉的同心环、放射状扇形和中心结构与最近在营养异质环境中生长的微生物菌落直接进行比较。至少一些埃迪卡拉盘状微生物可以与现存的在高盐微生物垫中生长的同心环形微生物菌落进行比较。由于埃迪卡拉纪盘状生物的大部分剩余记录可归因于非辐射模块化生物的固着结构，因此化石记录不支持确定后生动物的辐射祖先。
Enigmatic discoidal fossils are common in Neoproterozoic sedimentary sequences and in the stratigraphic record pre-date the first appearance of diverse Ediacaran fossil assemblages. Termed 'medusoids', these Neoproterozoic discoidal fossils have generally been interpreted as coelenterate-grade organisms implying a radially symmetrical body plan for ancestral eumetazoans. Analysis of exceptionally preserved discoidal fossils from the White Sea area, however, indicates that most of these discoidal forms represent colonial microbes. Localized pyritization, for example, reveals the presence of a conspicuous filamentous substructure in Ediacaria, whereas concentric rings, radial sectors and central structures in Cyclomedusa and Paliella compare directly with Recent microbial colonies growing in a nutritionally heterogeneous environment. At least some Ediacaran discoids can be compared with extant concentric ring-shaped microbial colonies that grow in hypersaline microbial mats. Insofar as most of the remaining record of Ediacaran discoids can be attributed to the holdfast structures of non-radiate modular organisms, there is no support from the fossil record for identifying a radiate ancestry for the Metazoa.