The study of the new and old collections of the Nikiti vertebrate localities included in this volume provides several new evidences for the taxonomy, composition, chronology and palaeoecology of these late Miocene mammal faunas. The faunal list of both primate bearing localities is enriched and improved by addition of new taxa and revision of older identifications; two new species are recognized in the Nikiti 2 (NIK) fauna (two hipparionine horses) and one subspecies from Nikiti 1 (NKT) is upgraded to the species level. The NKT and NIK faunas include 15 and 19 mammalian taxa, respectively. The mammalian faunas from both sites consist of almost the same families; the absence of some of them in NKT or NIK is most probably artificial. The chronology of the Nikiti mammal assemblages is based on biochronological data only, which allow the correlation of NKT to the terminal Vallesian (between 9.3 and 8.7Ma) and that of NIK to the earliest Turolian (between 8.7 and 8.3Ma). Concerning their age in relation with other neighboring mammal assemblages, NKT is younger than Ravin de la Pluie (Axios Valley, Greece) and isochronous or slightly older than Grebeniki (Ukraine). The NIK assemblage is older than Ravin des Zouaves 5 (Axios Valley) and Sivas (Turkey), dated at ∼8.2Ma and ∼8.3Ma, respectively. The available morphoecological, dental microwear-mesowear, and enamel isotopic analyses of the herbivores, as well as study of the phytolites suggest an open-light cover landscape for both localities. As documented previously in the Axios Valley, the Nikiti mammal fauna exhibits a significant reorganization through the Vallesian/Turolian boundary, including the Ouranopithecus/Mesopithecus replacement. However, this faunistic event is not consistent with the results of independent studies (isotope, dental wear, etc.) that fail to confirm significant climatic or vegetational changes across the same time interval.