New Maikhanellid Shells and Siphogonuchitid Spicule Bundles from the Cambrian Fortunian Stage of South China

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• 作者：Yunhuan LIU ; Yanan ZHANG ; Tiequan SHAO ; Hanhua TANG ; Kaituo JIANG ; Qi WANG ; Cheng CHEN ; Junyan DONG ; Yongchun LIANG ; Jun DAI and Jiaqi XUE
• 刊名：Acta Geologica Sinica - English Edition
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：90
• 期：5
• 页码：1629-1636
• 全文大小：7536K
• ISSN：1755-6724

文摘

Maikhanellids are a distinct group of Cambrian Fortunian small shelly fossils by the cap-shaped profiles and scaly shell ornamentation. According to the individual shell shape and ornamentation feature types of SO maikhanellids fossils which were collected from Xixiang botia, we confirmed the family Maikhanellidae content of six genera, which are Maikhanella, Ramenta, Purella, Ramentoides, Yunnannopleura and Mediata. Unlike the halkieriid animals whose shells and spicules are articulated on different body parts, maikhanellids were presumably yielded by siphogonuchitid spicules penetrating the intermediate matrix (the “spicule shell” hypothesis), and this is the reason that some researchers treated maikhanellids and co-occurring siphogonuchitids as synonyms. The affinities of Maikhanellids and siphogonuchitids remain debatable. Here, we report three dimensionally phosphatized maikhanellid shells and siphogonuchitid spicule bundles from the Cambrian Fortunian small shell faunas of South China. They differ from all the previously reported maikhanellids and siphogonuchitids, and may represent new types. The intact and smooth surface underneath the partially preserved scales of the shells challenges the “spicule-shell” hypothesis. The present siphogonuchitid spicules differ from the maikhanellid scales in size, morphology, and arrangement pattern, thus the spicules might not be derived from the shells. Whether the shells and spicule bundles were articulated on different body parts of the same animals remains unknown.