Fig. 1.

The relationship between measured Δ₄₇ values from bioapatite and the body temperature of the organism. The Y-value for each data point represents the mean Δ₄₇ value derived from 3–7 measurements of distinct extractions of CO₂ from tooth bioapatite. Y-axis error bars represent the external precision of the measurement, to one standard error. The X-axis scale shows the predicted body temperature of each species, based on previous studies on their thermoregulation, as described in detail in the main text. X-axis error bars represent uncertainties in body temperatures. (A) Δ₄₇ data plotted against temperature, reported in °C. (B) The same data plotted as 10⁶/T² [T in Kelvin]. The inorganic calcite calibration derived by Ghosh et al. is plotted as a dotted line (31). Δ₄₇ measurements of CO₂ extracted from bioapatite all fall within one standard error of the inorganic calcite line.