For billions of years, microbiota have been breaking down substrates and decomposing organic matter; a process known as microbioerosion. Traces left behind by microbes are understudied, but appear in bones throughout the fossil record. The morphology of these traces and their chemical signatures can shed light on the taphonomy of various assemblages. This study aims to document the microbial taphonomy of the Cretaceous fossils collected from the Dakota Rose Bonebed (DRB), near Milbank, South Dakota. More than 450 cross sections of microfossil bone were documented through 1,006 micrographs using both optical microscopy and scanning electron microscopy (SEM).  Various forms of microbial traces were revealed through optical microscopy and SEM, including two predominant tunnel morphologies. One is associated with perimeters of bone fragments, representing the presence of cyanobacteria. The other occurs within bone microstructure, representing either fungal or bacterial tunneling, or potentially a mixture of both. Spongiform porosity, the increase of bone pore spaces caused primarily by bacteria, is present in most of the bones with substantial loss of histology. Chemical microbial traces were determined through compositional analysis using μ-XRF and SEM. Substantial amounts of pyrite and secondary apatite proved to be the most abundant overall signatures of microbioerosion.  The microfossils of the DRB not only provide insight to microbe-induced destruction, but microbe-induced preservation in marine assemblages. Pyrite formation and apatite reprecipitation both cause rises in pH, which increases carbonate clumping. While microbioerosion describes the breakdown of bone and other substrates by microbiota, microbial processes can also facilitate diagenesis through changes to environmental chemistry.