Fig 1. Oxygen isotopic evidence and the effect of regional endothermic taxa in previous paleotemperature estimates.

(A-C) Difference in the δ¹⁸O value between coexisting cretoxyrhinids/otodontids and ectothermic taxa in several localities/sedimentary beds plotted against the ectothermic taxa δ¹⁸O value (as a proxy of seawater temperature). Three different regression analyses have been performed: (A) including all cretoxyrhinids-otodontids and all associated ectothermic taxa, (B) including all cretoxyrhinids-otodontids and only associated pelagic ectothermic taxa; and (C) including only cretoxyrhinids-otodontids and associated pelagic ectothermic taxa from Kocsis et al. [38] (regression lines are showed with associated 95% confidence intervals). Details of each fossil locality (denoted by numbers) are given in Table 1 and S1 Table. (D) Regression analyses performed in living lamnid sharks for comparative purposes, considering direct water and body temperature records compiled in Lowe and Goldman [25] (DM, deep muscle; ST, stomach). In all cases, slope values close to -1 imply that body temperature is independent from that of the water, slope values close to 0 imply a complete dependence, and intermediate slope values indicate some degree of independence. (E-F) Campanian-Maastrichtian latitudinal gradients of δ¹⁸O and seawater temperature calculated from cretoxyrhinids and ectothermic taxa. (G-H) Campanian-Maastrichtian δ¹⁸O and seawater temperature estimates calculated for three different latitudinal ranges (11°-13°, 20°-23° and 36°-49°), considering only cretoxyrhinids (pink), all taxa (black) and only ectothermic taxa (green). Significance of pairwise mean contrasts are shown in each case. Data in E-H taken from Puceat et al. [42]. ** indicates significance at the 0.05 level and * indicates significance at the 0.1 level.