摘要：Reconstructing the diet of Early Cretaceous birds is crucial for comprehensively understanding the evolution of early birds and the Mesozoic terres- trial ecosystem. Nowadays the stable carbon isotopic composition of bone hydroxylapatite (813CB-HA) pro- vides an effective way to analyze the paleodiet, how-ever, no research applied to early birds has been re-ported yet. In this study, bones from four Early Cre- taceous birds including Confuciusornis and Sape- ornis were collected for Fourier Transform Infrared(FTIR) analysis, to preliminarily determine whetherthe 813CB-HA-based paleodietary analysis was feasi-ble for early birds. FTIR spectra of Confuciusornis STM 14-112. Sapeornis STM 15-27, and Sapeornis STM 15-7 present characteristic absorption peaks of H2O, PO3; and Co2 which are comparable to those of modern hydroxylapatite. Their FTIR indexes in- cluding PCI (3.18-3.41), Ca/P (0.27-0.30) and co2- contents (7.71-8.25%) fall within the corresponding ranges of modern vertebrates (<4.3, 0.15-0.7. 2- 13.4%, respectively), further indicating those early bird's bones are less affected by diagenesis duringburial. Therefore, the 813CB-HA values of Confuciu- sornis STM 14-112. Sapeornis STM 15-27, and Sa- peornis STM 15-7 could effectively reflect their di- ets. While the FTIR spectrum of Sapeornis STM 15- 33 shows peak (at 710 cm) that indicating calcite, and its Co2- content (13.7%) is greater than the modern hydroxylapatite's, suggesting the bone ofSapeornis STM 15-33 is contaminated and the diet information that initially contained in its 813CB-HA value is altered. In general, both FTIR spectra and FTIR indexes of the Early Cretaceous birds show that the 813CB-HA method is feasible in reconstructing the early birds' diet, and the contamination test be- fore &13CB-HA analysis is necessary.
