Fig. 2.

Carbon and oxygen isotype ratios in fossil mammalian teeth from the Fayum Depression, Egypt, compared with similar data from living and extinct mammals. (A) δ¹⁸O and δ¹³C data from late Eocene mammals from Egypt. (B) δ¹³C versus standard deviation of δ¹⁸O for a range of mammalian taxa. Each data point represents average values for one taxon. Taxa falling in the dark gray band (SD δ¹⁸O < 0.5‰), are considered aquatic, whereas taxa in the larger light-gray field (SD δ¹⁸O > 1.0‰) are likely to be terrestrial. Additional data are from Clementz et al. (25, 26) and Kingston and Harrison (39). All δ¹⁸O standard deviations are calculated from values normalized relative to standard mean ocean water (SMOW) (modern value). δ¹³C error bars are shown at 1σ for Fayum taxa only. PDB, Pee Dee Formation belemnite standard; POM, particulate organic matter.