Bioerosion on vertebrate remains from the Upper Cretaceous of the Haţeg Basin, Romania and its taphonomic implications

Abstract

Bioerosion on fossil bones offers significant insights into both trophic relationships of ancient ecosystems and vertebrate taphonomy. Here we report six distinct trace fossil categories identified on isolated turtle, crocodyliform and dinosaur remains from the Upper Cretaceous Sînpetru Formation of the Haţeg Basin (Romania), for which five different probable tracemakers are identified: (1) termites, (2) dermestid beetles, (3) multituberculate mammals, (4) ziphodont theropod dinosaurs or crocodyliforms, and (5) plants. This extraordinary diversity of bioerosional trace fossils on vertebrate remains reveals insect-vertebrate as well as vertebrate-vertebrate interactions previously undocumented in the continental uppermost Cretaceous of Romania. The association between different traces, especially since many of these are superimposed on top of each other, allows the reconstruction of the detailed taphonomic history of the specimens, indicating four different taphonomic pathways. The vertebrate remains with trace fossils described here were most likely exposed to post-mortem biotic interactions for a prolonged time period before they were transported and/or trampled and finally buried. In the palaeoenvironmental context of a heterogeneous braided river system with low-lying wetlands and more elevated drylands, the death of the vertebrates as well as the scavenging likely occurred on the drylands.