Polymer segmental dynamics, center-of-mass chain diffusion, and nanoparticle (NP) diffusion are directly measured in a series of polymer nanocomposites (PNC) composed of very small (radius approximate to 0.9 nm) octa(aminophenyl) polyhedral oligomeric silsesquioxane (OAPS) NPs and poly(2-vinylpyridine) (P2VP) of varying molecular weight. With increasing OAPS concentration, both the segment reorientational relaxation rate (measured by dielectric spectroscopy) and polymer chain center-of-mass diffusion coefficient (measured by elastic recoil detection) are substantially reduced, with reductions relative to bulk reaching similar to 80% and similar to 60%, respectively, at 25 vol % OAPS. This commensurate slowing of both the segmental relaxation and chain diffusion process is fundamentally different than the case of PNCs composed of larger, immobile nanoparticles, where the motion of most segments remains relatively unaltered even though chain diffusion is significantly reduced. Next, using Rutherford backscattering spectrometry to probe the NP diffusion process, we find that small OAPS NPs diffuse anomalously fast in these P2VP-based PNCs, reaching diffusivities 10-10000 times faster than predicted by the Stokes-Einstein relation assuming the melt zero-shear viscosity. The OAPS diffusion Mw coefficients are found to scale very weakly with molecular weight, M-w(-0.7+/-0.1), and our analysis shows that this characteristic OAPS diffusion rate occurs on intermediate microscopic time scales, lying between the Rouse time of a Kuhn monomer tau(0) and the Rouse time of an entanglement strand tau(e). Our findings suggest that transport of these very small, attractive nanoparticles through well-entangled polymer melts is consistent with the recently reported vehicle mechanism of nanoparticle diffusion.