A New Ichnospecies of Cubiculum from Upper Cretaceous Dinosaur Bones in Western Argentina

Abstract

The new ichnospecies Cubiculum levis is described as a bowl-shaped bioerosion trace fossil in dinosaur bone from the Upper Cretaceous of western Argentina. The systematic description is based on specific ichnotaxobases for bioerosion trace fossils in bones. The main characteristics of the new ichnospecies are its general bowl-shaped morphology with marked concavity of the flanks and bottom, marked constriction of walls in the upper area, and the absence of bioglyphs in the interior surface. To establish a hierarchical approach to the taxonomy of Cubiculum, we propose an emended diagnosis for this ichnogenus. Based on comparative analysis with structures of fossil pupal chambers and results of actualistic experiments with carrion insects, the ethology of C. levis is interpreted as Pupichnia. Paleoenvironmental conditions at the paleontological site, taphonomic data and the morphology of C. levis indicate a continental arthropod producer with the biological and anatomical ability to bore bone. The producer was probably a Cretaceous coleopteran with a heavily sclerotized body and well-developed biting mouthparts. We emphasize the importance of establishing paleoethologic and paleobiologic inferences based on testable data provided by multiple sources, such as biology, physiology, sedimentology, and forensic sciences. Finally, we cite some relevant reports of traces fossils in bones interpreted as pupal chambers and we discuss the conflicting interpretations of their producers and ecological significance.