Taphonomic properties of the foot claw sheath from an Early Cretaceous bird specimen Confuciusornis sanctus

Abstract

Fossil claw sheaths of feathered dinosaurs and early birds from the Jehol Biota are not rare, but little research has been done on their microstructures and taphonomy. In this study, we analyzed a foot claw sheath of a Lower Cretaceous bird specimen Confuciusornis sanctus using scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDX) as well as Raman spectroscopy. The results revealed a calcium phosphate composition, and phosphatized corneocytes were recognized. The taphonomic environment is also briefly discussed, indicating that the conditions favorable for phosphatization are similar in both marine and non-marine environments. We further recognize phosphatization as a third taphonomic pathway of the Jehol Biota in addition to the two previously recognized pyritization and carbonaceous compression pathways, which may help explain the exceptional preservation of its soft tissues.