Luzon predators: Clues from a fossil with bite marks

Abstract

Luzon Island remained isolated throughout its emergent history with its paleofauna often considered depauperate. However, the terrestrial vertebrate fossil record of the island is still poorly known. A new fossil-bearing paleochannel deposit was discovered in La Union Province, northwestern Luzon, Philippines. This paleochannel is inferred to be of Pleistocene age and has yielded fossils tentatively classified as a bovid (Bubalus sp.), a cervid (Rusa sp.), a suid (Sus sp.), and a large crocodile (Crocodylidae). Interestingly, a proximal fragment of the left tibia of a cervid shows multiple bite marks. This study analyzes the bite marks and modifications on the specimen to infer its possible trace maker and explore its implications in understanding the ancient predatory guild of Luzon. Three sets of modifications were recognized on the specimen, namely the bite marks, the broken proximal end and the dry bone fractures. A crocodilian agent for the bite marks is supported by the bisections, their occurrence in the paleofaunal assemblage and the fluvial setting of the deposit. However, an unknown carnivoran agent interpretation cannot be fully disregarded given the ambiguity of bisected marks and the possibly gnawed proximal end of the specimen. Unfortunately, given the lack of in situ context and apparent overprinting, the extent of the peri- and post-mortem modification remains uncertain which hinders the identification of the predatory agent. Verification of the observations reported in this study would require the systematic collection and detailed taphonomic analysis of additional fossil specimens from the deposit.