Exceptional soft tissue fossilization of a Pleistocene vulture (Gyps fulvus): New evidence for emplacement temperatures of pyroclastic flow deposits

Volcanic sediments are often unsuitable for the fossilization of both hard and soft organic tissues, however, in some circumstances, they can provide unusual conditions for the preservation of remains. Here we report an exceptional case of soft tissue fossilization of a Late Pleistocene Eurasian griffon vulture (Gyps fulvus) in the pyroclastic sequence of the Alban Hills volcanic region (SE Rome, Italy). CT analyses have revealed an exceptional natural cast of the complete head and neck that preserve extraordinary detail including the fossilized everted tongue, beak, feather insertions and the first record of the nictitating membrane of the eye. This fossilization (superior in detail even to the victims of the AD 79 Plinian eruption of Vesuvius) reveals no evidence of burning and requires re-evaluation of the thermal constraints in operation for the preservation of organic materials within pyroclastic sediments. The analysis of the external morphological features has provided key information regarding the taphonomic processes in operation, the emplacement temperatures of distal pyroclastic flow deposits and the relationships between organic materials and low temperature phreatomagmatic flows. This sheds light not only on the extremely rare situation of fossilization in volcanic contexts but also provides a new perspective on taphonomic studies of highly detailed casts of fossil vertebrates.