Stable carbon isotope composition of bone hydroxylapatite: significance in paleodietary analysis

The stable carbon isotope composition of the structural carbonate derived from animal bone hydroxylapatite (delta C-13(B-HA)) could record an animal's diet. These records provide critical evidence for different paleontological disciplines, e.g., paleodiet analyses, and paleoclimate reconstructions. Compared to those of other body tissues, such as bone collagen or teeth enamel hydroxylapatite, delta C-13(B-HA) values record information on the whole diet of an animal in its last years. delta C-13(B-HA) can be applied to fossil animals of various body sizes. The delta C-13 analytical instruments available only require that prepared bone samples be approximately 2-5 mg for precise measurement, allowing delta C-13(B-HA) analysis to be feasible on most vertebrate fossils without destructive sampling, especially on small mammals or birds whose teeth are not large enough for sampling or are lost. Moreover, delta(13)C(B-HA )can be used from different times or under less than ideal burial environments. For fossils dating back to Devonian or buried in hot and humid regions, dietary information has been completely lost in bone collagen during post-depositional processes but still remained in the delta C-13(B-HA) values because hydroxylapatite is less influenced by diagenetic effects after deposition. In addition, systematic methods such as X-ray diffraction and Fourier transform infrared spectroscopy have been developed to qualitatively or semiquantitatively assess the influence of diagenesis on bone hydroxylapatite to ensure the credibility of the delta(13)C(B-HA )values. With the above merits, delta C-13(B-HA) analysis is therefore becoming an increasingly important method in paleodiet-related research. Currently, applications of the delta(13)C(B-HA )method on fossil animals are primarily focused on two aspects, namely, paleodietary reconstruction of fossil animals with uncertain diets and paleoenvironmental reconstruction based on the delta(13)C(B-HA )values of fossil herbivores. The published researches, combined with our new results from early birds, demonstrate the considerable significance of the delta C-13(B-HA) method in paleontological and paleoenvironmental research. Notably, the delta C-13(B-HA)-based paleodietary analysis of early vertebrates, especially the large number of small birds or mammals discovered in the past decades would be an important work in the near future. (C) 2021 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.

Automated summary

The stable carbon isotope composition of animal bone hydroxylapatite can record an animal's diet and has become an increasingly important method in paleodiet-related research. It can be applied to fossil animals of various body sizes and is feasible for analysis on most vertebrate fossils without destructive sampling. Moreover, it can provide dietary information even for fossils dating back to Devonian or buried in hot and humid regions.