Discovery of the oldest bilaterian from the Ediacaran of South Australia
Discovery of the oldest bilaterian from the Ediacaran of South Australia
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DOI：
10.1073/pnas.2001045117
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发表时间：
2020-04-07
影响因子：
11.1
通讯作者：
Droser, Mary L.
中科院分区：
文献类型：
--
作者：
Evans, Scott D.;Hughes, Ian V.;Droser, Mary L.
对现代动物和埃迪卡拉纪遗迹化石的分析预测，最古老的两侧对称动物是简单而小的。这些生物很难在化石记录中识别出来，但应该是埃迪卡拉生物群的一部分，埃迪卡拉生物群是最早保存下来的宏观复杂动物群落。在这里，我们描述Ikaria wariootia gen. et sp. nov.从埃迪卡拉成员，南澳，一个小的，简单的有机体与前/后分化。我们发现伊卡利亚的大小和形态与遗迹化石Helminthoidichnites祖先的预测相匹配，这表明了流动性和沉积物位移。在Ediacara段，Helminthoidichnites在地层上出现在经典Ediacara体化石之下。总之，这些都表明，伊卡利亚代表了最古老的总组bilaterians确定从南澳之一，几乎没有偏离的字符预测为他们最后的共同祖先。此外，这些遗迹化石持续到中生代，提供了埃迪卡拉纪和寒武纪动物之间的关键联系。
Analysis of modern animals and Ediacaran trace fossils predicts that the oldest bilaterians were simple and small. Such organisms would be difficult to recognize in the fossil record, but should have been part of the Ediacara Biota, the earliest preserved macroscopic, complex animal communities. Here, we describe Ikaria wariootia gen. et sp. nov. from the Ediacara Member, South Australia, a small, simple organism with anterior/posterior differentiation. We find that the size and morphology of Ikaria match predictions for the progenitor of the trace fossil Helminthoidichnites-indicative of mobility and sediment displacement. In the Ediacara Member, Helminthoidichnites occurs stratigraphically below classic Ediacara body fossils. Together, these suggest that Ikaria represents one of the oldest total group bilaterians identified from South Australia, with little deviation from the characters predicted for their last common ancestor. Further, these trace fossils persist into the Phanerozoic, providing a critical link between Ediacaran and Cambrian animals.