Stable‐isotope studies on the collagenic and hydroxylapatite components of fossils: Palaeoecological implications

Abstract

Collagenic material has been extracted and analysed for stable carbon- and nitrogen-isotope ratios from Henschke Cave, a Late Pleistocene fossil locality, South Australia. The carnivore Thylacoleo carnifex most likely consumed omnivores (Parameles spp.) with a palaeodiet of C3 plant material under a forest canopy, which was also recorded in the herbivores analysed (Macropus spp., Sthenurus spp. and Diprotodon spp.). A forested environment supports previous interpretations of extant fauna and their modern habitats. The presence of negative nitrogen-isotope ratios in herbivores has been interpreted as non-diagenetic on the basis of carbon/nitrogen ratios and amino acid spectra, and in fact may be indicative of acidic soils. Analyses on bone and enamel carbonate hydroxylapatite from the same species support the conclusion that bone is unreliable for palaeoecological and palaeoclimatological research. However, bone carbonate hydroxylapatite may prove valuable in assessing the extent of isotopic fractionation during diagenesis. A review of carbon-isotope analyses on fossil collagenic material and enamel carbonate hydroxylapatite suggests a carnivore-herbivore boundary. The application of this boundary in palaeoecological research requires further investigation. Future palaeoecological research on fossils needs to incorporate stable-isotope analyses on the carbonate hydroxylapatite and collagenic components of fossils.