A taphonomic investigation of Late Miocene mammal bones and teeth and a taxonomic study of the abundant and diverse giraffid material from Kerassia, Greece, were undertaken. The material was collected from seven different sites near Kerassia, where at least two fossiliferous horizons occur. Microbial action caused extensive destruction in almost all the examined specimens of bone and teeth tissues from both horizons. Despite this, and contrary to the established ideas, bioeroded tissues survived to become fossils, preserving their histological and bioerosion features. The diameters of the microtunnels (150-600 nm) in the destructive foci indicate that the invading microorganisms were bacteria. Recrystallization of the apatite crystallites in the foci of damaged tissues occurred immediately after the end of bacterial activity, restraining later diagenetic recrystallization. This process is responsible for differences in the chemistry of the three structural areas of the bioeroded tissues, the undamaged areas, the foci and the rims of the foci. X-ray diffraction mineralogical analyses showed that fossil bone and dentine consist of carbonate fluorapatite and enamel consists of carbonate hydroxyapatite. The crystallinity of the fossil tissues is not age dependent but rather reflects the type of the hard tissue and the conditions of the local burial environment. To date, five different species of giraffes have been determined in Kerassia. Four species were found in the lower horizon, Palaeotragus rouenii, Palaeotragus sp., Samotherium major and Helladotherium duvernoyi and four species were found in the upper horizon Palaeotragus rouenii, Samotherium major, Helladotherium duvernoyi and Bohlinia attica. Finally, this study shows that a seasonal Mediterranean type, relatively temperate to warm and moist climate, can be inferred for the MN12 (Middle Turolian) of the Kerassia region.