Rare earth element (REE) signatures can be used to identify the original mode of deposition of fossil bones and teeth that have been reworked. This new technique may resolve the notoriously difficult problem of assessing the amount of transport or reworking undergone by fossil bones and teeth on the basis of physical parameters, such as degree of abrasion. Different REE signals characterize different pore-water environments. Bones and teeth, composed of apatite, incorporate REEs rapidly during early diagenesis, and the REE signature in the bone is controlled by that of the surrounding pore waters. Reworked bones and teeth may show REE traces suggesting early-diagenetic pore-water conditions different from those indicated by in situ sedimentary or geochemical evidence. This situation is demonstrated in a case study from the Rhaetian (latest Triassic) of southwest England, where different bone beds are compared. In one case, the original environmental setting of reworked bone is traced by matching REE traces with contemporaneous unreworked bone assemblages in neighboring areas.