Belemnite biomineralization, development, and geochemistry: The complex rostrum of Neohibolites minimus
Belemnite biomineralization, development, and geochemistry: The complex rostrum of Neohibolites minimus
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箭石生物矿化、发育和地球化学：Neohibolites minimus 的复杂讲台
DOI：
10.1016/j.palaeo.2016.12.022
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
--
作者：
Fuchs;D.;Reitano;A.;Insacco;G.;Iba;Y.
蛭石是一种已灭绝的胶体类头足类动物，是中生代海洋生态系统的重要组成部分。在生物地层学和地球化学研究中有广泛的应用。岩台的保存状态是其地球化学资料解释的关键因素。然而，它们的保存很难评估，因为没有现代头足类动物形成钙质喙。作为内部骨骼的喙部的生物矿化过程对大多数物种来说知之甚少。这也适用于上乳，这是一种晚期个体发育的延伸，只存在于一些蛭石物种中。这个角色的主要结构和功能至今仍有争议。我们研究了Albian早白垩世最小新黑闪岩（neohibolites minimus）的正、正辉岩的微观结构、稳定同位素（δ13C、δ18O）和元素组成（Mg/Ca、Sr/Ca、Fe/Ca、Mn/Ca）。为了进行比较，我们研究了阿尔戈（Argonauta argo）。这些新近的章鱼形成了一个钙质外壳。n的正、外平。最小的显示微观结构和地球化学差异。阴极发光显微镜和球辉石的显微结构表明，所研究的球辉石中的蓝色/橙色发光生长线主要是原生生物矿化现象，而不仅仅是成岩作用的结果。根据部分与舡鱼壳的相似性，我们认为蛭石表乳的内部部分是原始有机顶端线的延续。讨论了上乳作为一种潜在的性选择性状的发育和进化。保存完好的上乳方解石比正乳方解石具有更高的元素/钙比，表明对这些值有重要影响。我们进一步发现了代谢和动力学分馏对稳定同位素特征产生重要影响的证据。我们的发现表明所研究的地层具有复杂的矿化过程。不同的显微结构具有不同的地球化学特征。生命效应在讲台地球化学中起着重要作用，使讲台作为古气候档案的应用复杂化。
Belemnites, a group of extinct coleoid cephalopods, were important components of Mesozoic marine ecosystems. Their calcitic rostra are extensively used in biostratigraphy and geochemistry. The preservation state of the rostra is a crucial factor for the interpretation of their geochemical data. However, their preservation is difficult to assess, since no modern cephalopod forms calcitic rostra. The biomineralization process of the rostrum, which functioned as an internal skeleton, is poorly understood for most species. This also applies for the epirostrum, a late ontogenetic extension of the rostrum which is only present in some belemnite species. The primary structure and function of this character are still being debated controversially.We have investigated the microstructure, stable isotope (δ13C, δ18O), and elemental composition (Mg/Ca, Sr/Ca, Fe/Ca, Mn/Ca) of both, ortho- and epirostra of the belemnite speciesNeohibolites minimus(Early Cretaceous, Albian). For comparison, we studied argonauts (Argonauta argo). These recent octopuses build a calcitic shell. Ortho- and epirostra ofN.minimusshow microstructural and geochemical differences. Cathodoluminescence-microscopy and the microstructures of belemnites and argonauts indicate that blue/orange luminescent growth lines in the studied belemnites are largely a primary biomineralization phenomenon and not solely due to diagenesis. Based in part on analogy to argonaut shell, we suggest that the inner part of the belemnite epirostrum is a continuation of an originally organic apical line. The development and evolution of the epirostrum as a potential sexually selected character is discussed. Well-preserved epirostrum calcite has higher element/Ca ratios than the calcite of the orthorostrum, suggesting a vital effect affecting these values. We further found evidence for vital effects on the stable isotope signatures due to metabolic and kinetic fractionation.Our findings suggest a complex mineralization process of the studied rostra. Different microstructures with distinctive geochemical signatures occur in a single belemnite species. Vital effects played an important role in the rostrum geochemistry, complicating the application of the rostra as paleoclimatic archives.