Bone chip-filled burrows associated with bored dinosaur bone in floodplain paleosols of the Cretaceous Hasandong Formation, Korea
Abstract Borings in dinosaur bone, which are intimately associated with subjacent burrows filled with bone chips, are recognized from a Lower Cretaceous floodplain vertic–calcic paleosol, Dapyeongri, Korea. The bored bone is an in situ weathered scapula of herbivore. The borings are ubiquitous within and on scapula, and have diverse orientations. They are mostly solitary with diameters from a few millimeters to 1 cm. The bone chip-filled burrows have similar diameters to those of borings and occur sporadically just below (within 10 cm downwards) the scapula. Some burrows are isolated and some are clustered. Burrow direction is also variable, and some burrows are intertwined, forming networks. The bone borings and related bone chip-filled burrows post-dated bone weathering processes such as cracking, fracturing, brecciation, and disintegration, which indicates that Dapyeongri bone borers preferred to feed upon dried skeleton. Dermestid beetles are the most likely organism for Dapyeongri bone borers and burrowers, considering that it is the most common carrion insect inhabiting vertebrate carcasses in dry decay stage. These bone borings and bone chip-filled burrows provide evidence that dermestid beetles played an important role as the last scavengers of dinosaur carcasses during the Early Cretaceous. Such scavenging by carrion insects under dry climate may have impacted negatively the dinosaur fossil preservation in Cretaceous deposits. The behavior of Dapyeongri bone borers/burrowers is compared with that of dung beetles documented from the Upper Cretaceous Two Medicine Formation [Chin and Gill, Palaios 11 (1996) 280–287], which cache subterranean burrows with organic matter transported from the surface. These unique trace fossils thus provide additional evidence for understanding Cretaceous trophic interaction between dinosaurs and insects.