Fig. 3

Oxygen isotope composition of select vertebrate fossils from the Máriahalom site as a function of water isotopic composition. Sharks reflect seawater isotopic composition and habitat temperature (see isotherms, Lécuyer et al., 2013). It is noted that a -0.3 ‰ of seawater values was used for the Early Miocene (Lear et al., 2000), and the related marine isotope data from the shark teeth are plotted along this value. Crocodiles (cf. Diplocynodon sp.) most probably lived in brackish environments (Amiot et al., 2007), while mammals show the low negative δ¹⁸O_H2O of the drinking water source (Kohn & Cerling, 2002). It is noted that the dentine and bone (sirenian) analyses have lower δ¹⁸O_PO4 compared to the enameloid/enamel that interpreted here as a sign of early diagenetic alteration in the presence of low δ¹⁸O_H2O water