CNIDARIAN TAPHONOMY AND AFFINITIES OF THE EDIACARA BIOTA
CNIDARIAN TAPHONOMY AND AFFINITIES OF THE EDIACARA BIOTA
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DOI：
10.1111/j.1502-3931.1989.tb01439.x
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发表时间：
1989-10-15
期刊：
影响因子：
1.5
通讯作者：
NORRIS, RD
中科院分区：
文献类型：
--
作者：
NORRIS, RD
现存的水母，chondrophoran，和pennatulid的石膏印模和砂铸件共享基本的结构特征与化石在上元古界埃迪卡拉组合。现存的水母和元古代的圆形压痕的immagnesium表现出放射状和同心结构和中央凸起的凸台的安排和位置的一般相似性。但元古宙化石中的环纹和放射状沟纹较多，强烈褶皱或变形的化石与现代水母类化石相比较为少见。现代的企鹅化石比元古宙的Charniodiscus更变形和不规则。更大的频率变形的最刺激的化石水母相对于前寒武纪圆形的印象意味着，元古代水母比许多现代类群可比的大小。在这里研究的现存形式中，许多具有丰富圆环的化石没有结构对应物，它们的水母类亲缘关系应该仍然存在疑问。Ediacara生物和现存刺胞动物的印象结构简单，这表明它们的相互相似性可能是由于趋同。然而，没有令人信服的形态学理由来拒绝一些元古代化石可能与活刺胞动物有亲缘关系的说法。
Plaster impressions and sand casts of extant medusae, a chondrophoran, and a pennatulid share basic structural characteristics with fossils in the Upper Proterozoic Ediacara assemblage. Impressions of extant medusae and Proterozoic circular impressions show general similarities in arrangement and position of radial and concentric structures and a central raised boss. However, annular rings and radial grooves are more numerous in the Proterozoic fossils and strongly folded or deformed fossils are rare as compared with impressions of modern medusae. Recent pennatulids yield impressions that are more deformed and irregular than the Proterozoic genus Charniodiscus. The greater frequency of deformation of most stimulated fossil medusoids relative to Precambrian circular impressions implies that Proterozoic medusoids were substantially stiffer than many modern taxa of comparable sizes. Many fossils with abundant circular rings have no constructional counterparts among the extant forms studied here and their medusoid affinities should remain in doubt. The structural simplicity of impressions of Ediacara organisms and extant cnidarians suggests that their mutual similarities may be due to convergence. However, there is no compelling morphological reason to reject the claim that some Proterozoic fossils may share affinities with living cnidarians.