New data on molluscs and their shell microstructures from the Middle Cambrian Gowers Formation, Australia
New data on molluscs and their shell microstructures from the Middle Cambrian Gowers Formation, Australia
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DOI：
10.1111/j.1475-4983.2009.00922.x
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发表时间：
2010-01
期刊：
影响因子：
2.6
通讯作者：
M. Vendrasco;S. Porter;Artem V. Kouchinsky;Guoxiang Li;Christine Z. Fernandez
中科院分区：
文献类型：
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作者：
M. Vendrasco;S. Porter;Artem V. Kouchinsky;Guoxiang Li;Christine Z. Fernandez
摘要：在澳大利亚乔治娜盆地中寒武世Gowers组（Ptychagnostus atavus/Peronopsis opimus带，Floran阶）的软体动物中发现了许多新的保存壳微结构的案例。新的数据提供了进一步的证据，即到中寒武世，软体动物的外壳微结构是多样的，许多软体动物具有复杂的外壳，具有多种类型的外壳微结构。此外，本文还描述了许多新出现的层状微结构。对于许多物种来说，这些层状微结构的性质尚不清楚，但在三个物种中，微结构是叶状方解石，至少有两个物种的微结构更可能是方解石半珍珠层，这是一种在腕足动物和苔藓虫中已知的微结构，但在现代软体动物中未知。这三个密切相关的lophotrochozoans之间的共性强调了类似的生物矿化机制。此外，这些观察结果表明，中寒武世的软体动物中普遍存在方解石壳谱系，这是一个方解石海的时代。此外，在许多这些化石中广泛出现的层状珍珠质样微结构揭示了这些强大的（抗断裂）微结构在中寒武世软体动物中的分布情况。此外，一些Yochelcionella的标本保留了两侧对称的肌肉疤痕的印记。本文描述的新分类群包括Coryelophthorntoniensis gen.et sp. nov.，nov.，Saginata Yochelcionella saginata sp. nov.和Anhuiconus？阿格瑞农新种
Abstract: Numerous new cases of preserved shell microstructure were discovered in molluscs from the Middle Cambrian Gowers Formation (Ptychagnostus atavus/Peronopsis opimus Zone, Floran Stage) in the Georgina Basin, Australia. The new data provide further evidence that, by the Middle Cambrian, molluscan shell microstructures were diverse, and many molluscs had a complex shell with multiple types of shell microstructure. In addition, many new occurrences of laminar microstructures are described herein. For many, the nature of these laminar microstructures is not known, but in three species the microstructure is foliated calcite, and in at least two the microstructure is more likely to have been calcitic semi‐nacre, a type of microstructure known in brachiopods and bryozoans but unknown in modern molluscs. This commonality among these three closely related lophotrochozoans underscores a similar mechanism of biomineralization. Moreover, these observations suggest a prevalence of calcite‐shelled lineages among molluscs from the Middle Cambrian, a time of calcite seas. In addition, the broad occurrence of laminar, nacre‐like microstructures in many of these fossils reveals how widespread these strong (fracture‐resistant) microstructures were in Middle Cambrian molluscs. Additionally, a few specimens of Yochelcionella preserve imprints of a bilaterally symmetrical pair of muscle scars. New taxa described here include Corystos thorntoniensis gen. et sp. nov., Yochelcionella snorkorum sp. nov., Yochelcionella saginata sp. nov., and Anhuiconus? agrenon sp. nov.