Non-traditional isotope perspectives in vertebrate palaeobiology

The recent development of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) notably in the disciplines of earth sciences, now allows the precise measurement of isotope ratios, even at low concentration. Non-traditional isotope systems, such as alkaline earth (Ca, Mg) and transition (Cu, Fe, Zn) metals are now being measured in a variety of biological tissues, including bone and teeth. Although our understanding of the environmental and biological mechanisms behind the fractionation of such elements is still in its infancy, some of these isotopes are suspected to fractionate along the food chain, as has been reported in the literature for calcium, magnesium and zinc. Other geochemical methods, such as concentration analyses, permit a prior assessment of diagenesis in the fossils and such an approach indicates that in some circumstances, not only enamel but also dentine or bone can preserve its original biogenic composition. The aims here are to: review the current knowledge surrounding these various isotopic tools; address their potential preservation in biological apatite; and provide the palaeobiologist with a guide to the different toolkits available, including a discussion of their potential applications in vertebrate palaeobiology with a case study involving two mammal assemblages from the Pleistocene of Europe.

近年来，多接收器电感耦合等离子体质谱法（multi-collector inductively coupled plasma mass spectrometry, MC-ICP-MS）的技术进步，尤其在地球科学领域，现已可精准测定同位素比值，即便样品浓度极低也可完成检测。如今，包括碱土金属（钙Ca、镁Mg）与过渡金属（铜Cu、铁Fe、锌Zn）在内的非传统同位素体系，已可在骨、牙齿等多种生物组织中开展测定。尽管目前学界对这类元素分馏作用背后的环境与生物机制仍处于初步探索阶段，但已有文献报道钙、镁、锌的同位素可沿食物链发生分馏，因此推测部分其他同位素也存在类似分馏行为。其他地球化学分析方法（如浓度分析）可预先评估化石的成岩蚀变程度，此类研究表明，在部分场景下，不仅牙釉质，牙本质乃至骨骼均可保留其原始的生物成因组分。本研究的目标如下：其一，梳理当前针对各类同位素分析手段的研究进展与认知；其二，探讨这些同位素在生物磷灰石中的保存潜力；其三，为古生物学家提供一份现有分析工具的使用指南，并结合欧洲更新世两套哺乳动物化石组合的案例研究，讨论其在脊椎动物古生物学中的潜在应用价值。