Bioeroded Dinosaur Bones: Novel Signatures of Necrophagous Activity in a Cretaceous Continental Environment

We describe a novel type of arthropod bioerosion trace fossil, Amphifaoichnus seilacheri new igen., new isp., associated with sauropod bones from the Upper Cretaceous (Coniacian-Early Santonian) Plottier Formation of western Argentina. The specimens are preserved in distal-floodplain deposits. The new ichnotaxon consists of predominantly horizontal, unbranched, unlined, elongated tubes, emplaced at the interface of bone and sediment, but penetrating the bone cortical tissue as well. Fill consists of unconsolidated sediment with evenly distributed bone chips in the infill sorted by size. The presence of bone fragments within the structures indicates prior bioerosion of the bone and their subsequent emplacement as part of the trace fill. A coleopteran with a heavily sclerotized body and well-developed biting mouthparts is tentatively inferred as a tracemaker. Amphifaoichnus seilacheri is interpreted as fodinichnion, reflecting the activity of scavengers able to decompose dinosaur carcasses. This ichnotaxon represents a novel ethology and ecological linkage previously undetected in continental ecosystems.