My thesis explores how the information content of fossil Glires (rodents + rabbits) effects phylogenetic reconstruction and the implications for downstream analysis and interpretation. The first two chapters take a detailed look at the phylogenetic signal contained within fossil Glires, while the third and fourth chapters put interpretation of fossils into practice through analyses of phylogeny, biogeographic history, anatomy and geometric morphometrics. In the final chapter, I discuss the importance of my biogeographic, anatomical and phylogenetic results within the context of Glires evolution. I also recommend the inclusion of fossil data in total-evidence approaches where possible and give suggestions for future work.