Conodont elements are calcium phosphate (apatite structure) mineralized remains of the cephalic feeding apparatus of an extinct marine organism. Due to the high affinity of apatite for rare earth elements (REE) and other high field strength elements (HFSE), conodont elements were frequently assumed to be a reliable archive of sea-water composition and changes that had occurred during diagenesis. Likewise, the crystallinity index of bioapatite, i.e., the rate of crystallinity of biologically mediated apatite, should be generally linearly dependent on diagenetic alteration as the greater (and longer) the pressure and temperature to which a crystal is exposed, the greater the resulting crystallinity. In this study, we detected the uptake of HFSE in conodont elements recovered from a single stratigraphic horizon in the Upper Ordovician of Normandy (France). Assuming therefore that all the specimens have undergone an identical diagenetic history, we have assessed whether conodont taxonomy (and morphology) impacts HFSE uptake and crystallinity index. We found that all conodont elements are characterized by a clear diagenetic signature, with minor but significant differences among taxa. These distinctions are evidenced also by the crystallinity index values which show positive correlations with some elements and, accordingly, with diagenesis; however, correlations with the crystallinity index strongly depend on the method adopted for its calculation.

牙形石元素是已灭绝的海洋生物的头部进食装置的矿化磷酸钙（磷灰石结构）。由于磷灰石对稀土元素（REE）和其他高场强元素（HFSE）的高亲和力，通常认为牙形石元素是海水成分和成岩过程中发生的变化的可靠档案。同样，生物磷灰石的结晶度指数，即生物介导的磷灰石的结晶速度，通常应线性依赖于成岩作用，因为晶体所承受的压力和温度越大（和时间越长），所得的结晶度就越大。在这个研究中，我们在法国诺曼底上奥陶纪单一地层中发现的牙形质元素中检测到HFSE的吸收。因此，假设所有标本都经历了相同的成岩史，我们评估了牙形石分类学（和形态）是否会影响HFSE摄取和结晶度指数。我们发现，所有牙形石元素都具有清晰的成岩特征，在类群之间存在细微但重要的差异。这些区别也由结晶度指数值证明，该指数值与某些元素以及成岩作用呈正相关。然而，与结晶度指数的相关性在很大程度上取决于所采用的计算方法。我们评估了牙形石分类学（和形态）是否影响HFSE摄取和结晶度指数。我们发现，所有牙形石元素都具有清晰的成岩特征，在类群之间存在细微但重要的差异。这些区别也由结晶度指数值证明，该指数值与某些元素以及成岩作用呈正相关。然而，与结晶度指数的相关性在很大程度上取决于所采用的计算方法。我们评估了牙形石分类学（和形态）是否影响HFSE摄取和结晶度指数。我们发现，所有牙形石元素都具有清晰的成岩特征，在类群之间存在细微但重要的差异。这些区别也由结晶度指数值证明，该指数值与某些元素以及成岩作用呈正相关。然而，与结晶度指数的相关性在很大程度上取决于所采用的计算方法。这些区别也由结晶度指数值证明，该指数值与某些元素以及成岩作用呈正相关。然而，与结晶度指数的相关性在很大程度上取决于所采用的计算方法。这些区别也由结晶度指数值证明，该指数值与某些元素以及成岩作用呈正相关。但是，与结晶度指数的相关性在很大程度上取决于所采用的计算方法。