Dianulites Eichwald, 1829: An unusual Ordovician bryozoan with a high-magnesium calcite skeleton
Dianulites Eichwald, 1829: An unusual Ordovician bryozoan with a high-magnesium calcite skeleton
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Dianulites Eichwald，1829：一种不寻常的奥陶纪苔藓虫，具有高镁方解石骨架
DOI：
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发表时间：
1999
影响因子：
1.4
通讯作者：
Mark A. Wilson
中科院分区：
文献类型：
--
作者：
P. Taylor;Mark A. Wilson
本文用X射线衍射、扫描电镜、分析电镜和阴极发光等方法研究了奥陶纪狭孔苔藓虫Dianulites Eichwald，1829的“颗粒”壁微结构。再结晶的时间和存在的微晶白云石夹杂物的骨骼壁意味着原始骨架组成的高镁方解石（HMC）。虽然在一些现代唇口动物中发现了HMC，但在现存的狭唇苔藓虫中没有记录，但似乎也存在于Nicholsonella和其他几个传统上被分配到trepostomes或cystoporates的奥陶纪属中。Dianulites的俄罗斯模式种D. fastigiatus Eichwald，1829年，在北美犹他州的下奥陶统菲尔莫尔组（Fillmore Formation）中首次被修订和记录。在苔藓动物中，D. fastigiatus具有陀螺状、圆锥形或喇叭形菌落，直的到稍微弯曲的，在圆锥体的平坦、宽的端部上具有游动体开口;圆锥体的侧面包括钙化的外壁。这种生长形式类似于一些孤独的皱纹珊瑚和其他底栖动物，这些动物被认为除了顶部之外都埋在柔软的沉积物中。这样的解释是支持在Dianulites的稀缺epibionts外壁上的锥和发生的标本，包括堆栈的亚殖民地，这表明时期的部分埋葬的活组织的沉积物。
The ‘granular’ wall microstructure of the Ordovician stenolaemate bryozoan Dianulites Eichwald, 1829, has been studied using ultrathin sections, scanning electron microscopy (SEM), analytical SEM, and cathodoluminescence. The timing of recrystallization and the presence of microdolomite inclusions in the skeletal walls implies that the original skeleton consisted of high-magnesium calcite (HMC). Although found in some modern cheilostomes, HMC has not been recorded in living stenolaemate bryozoans, but appears to have also been present in Nicholsonella and a few other Ordovician genera traditionally assigned to the trepostomes or cystoporates. The Russian type species of Dianulites, D. fastigiatus Eichwald, 1829, is revised and recorded for the first time in North America from the Fillmore Formation (Lower Ordovician) of Utah. Unusually among bryozoans, D. fastigiatus has turbinate, cone- or horn-shaped colonies, straight to slightly curved, with zooids opening on the flat, broad end of the cone; the sides of the cone comprise calcified exterior walls. This growth-form resembles some solitary rugose corals and other benthic animals thought to have lived with all but their tops buried in soft sediment. Such an interpretation is supported in Dianulites by the scarcity of epibionts on the exterior walls of the cone and by the occurrence of specimens comprising stacks of subcolonies, suggesting periods of partial burial of the living tissues by sediment.