DOI: 10.5061/dryad.8gtht76zf
title: Supplementary data from: Reassessment of body temperature and thermoregulation strategies in Mesozoic marine reptiles

description: Ichthyosauria, Plesiosauria and Metriorhynchidae were apex predators in
 Mesozoic oceanic trophic networks. Previous stable oxygen isotope studies
 suggested that several taxa belonging to these groups were endothermic and
 for some of them homeothermic organisms. However, these conclusions remain
 contentious owing to the associated uncertainties regarding the δ18O value
 and oxygen isotope fractionation relative to environmental sea water.
 Here, we present new bioapatite phosphate δ18O values (δ18Op) of
 Ichthyosauria, Plesiosauria and Metriorhynchidae (Middle Jurassic to Early
 Cretaceous) recovered from mid- to high-paleolatitudes to better constrain
 their thermophysiology and investigate the presence of regional
 heterothermies. The intra-skeletal δ18Op variability failed to reveal
 distinct heterothermic patterns within any of the specimens, indicating
 either intra-body temperature homogeneity or an overriding diagenetic
 overprint of the original biological δ18Op bone record. Body temperature
 estimates have then been reassessed from new and published δ18Op values of
 well-preserved isolated teeth, recently revised Mesozoic latitudinal δ18O
 oceanic gradient and 18O-enrichment factor of fully aquatic air-breathing
 vertebrates. Our results confirm that Ichthyosauria were homeothermic
 endotherms (31°C to 41°C), while Plesiosauria were likely poikilothermic
 endotherms (27°C to 34°C). The new body temperature estimates of the
 Metriorhynchidae (25°C to 32°C) closely follow ambient temperatures and
 point to poikilothermic strategy with no or little endothermic abilities.
 These results improve our understanding of Mesozoic marine reptile
 thermoregulation and indicate that due to their limited body temperature
 variations, the δ18Op values from Ichthyosauria fossil remains could be
 used as valuable archives of Mesozoic oceans δ18Osw values that may help
 improve palaeoenvironmental and palaeoclimatic reconstructions.
description: # Supplementary data: Reassessment of body temperature and
 thermoregulation strategies in Mesozoic marine reptiles
 [https://doi.org/10.5061/dryad.8gtht76zf](https://doi.org/10.5061/dryad.8gtht76zf) ## Description of the data and file structure Please find here the supplementary data of the manuscript. It includes detailed isotope data, Raman spectroscopy data, body temperature estimates, and some additional figures. **Supplementary Table 1:** Oxygen and carbon isotope values (δ18Op, δ18Oc, δ13Cc), along with CO₃²⁻ and P₂O₅ content (wt%) of bioapatite extracted from the bones and teeth of Ichthyosauria, Plesiosauria, and Metriorhynchidae. Oxygen isotope values in bold represent data excluded from the dataset due to mineralogical alteration, while values in italics indicate data removed due to carbonate content exceeding 13.4 wt%. **Supplementary Table 2:** Environmental sea water temperature and Ichthyosauria, Plesiosauria and Metriorhynchidae new body temperatures using the equation of Lécuyer et al. (2013) and considering the latitudinal gradient of δ18Osw values of Alberti et al. (2020) and an 18O-enrichment of body water relative to environmental water of 0.8% for Mesozoic marine reptiles (Séon et al. 2023). The table compiles oxygen isotope data for the phosphate bioapatite from the teeth of these groups, organized by their geographical locations. Difference between old (Anderson et al. 1994, Bernard et al. 2010, Séon et al. 2020) and new body temperature estimates for Ichthyosauria, Plesiosauria and Metriorhynchidae according to palaeolatitude. **Supplementary Table 3:** Raman spectral parameters, including the position (ν₁- PO₄³⁻) and full width at half maximum (FWHM) of the ν₁-PO₄³⁻ peak, for bone and teeth samples of Ichthyosauria, Plesiosauria, and Metriorhynchidae. **Supplementary information 1:** Isotope-based body temperature calculations. **Supplementary Figure 1**: Boxplots showing the P2O5 content expressed in weight percentage of apatite (wt%) distribution of Mesozoic marine reptile bones and teeth along the fossil deposits (**A.**) and the specimens (**B.**). Outliers are plotted as white circles. The horizontal bars in the boxes correspond to the medians and the whiskers to the minimum and maximum values. **Supplementary Figure 2:** Boxplots showing the P2O5 content (wt%) distribution of bones sets for the specimens of Ichthyosauria (**A.** Ichthyosauria indet, **B.** *Keilhauia* sp., **C**. *Palvennia hoybergeti*), Plesiosauria (**D.** *Colymbosaurus svalbardensis* and **E.** Cryptoclididae indet., **F.** Elasmosauridae indet.,) and *Metriorhynchus* aff. *superciliosus* (**G.**). Asterisks indicate the significance of the observed differences between pair of groups: * for *p*-value &lt; 0.05, ** for *p*-value &lt; 0.01 and *** for *p*-value &lt; 0.001. Outliers are plotted as white circles. The horizontal bars in the boxes correspond to the medians and the whiskers to the minimum and maximum values. **Supplementary Figure 3**: Values of δ18Op (‰, V-SMOW) as a function of P2O5 content (wt%) according to mineralized elements (bones and teeth) in Ichthyosauria (**A.**) and Plesiosauria (**B.**). **Supplementary Figure 4**: δ18Oc values (‰, V-SMOW) versus carbonate content of the bones and tooth from the specimen of Ichthyosauria indet. **Supplementary Figure 5:** Comparison between previous body temperature in white (Bernard et al. 2010; Séon et al. 2020) and new body temperature estimates in black for Ichthyosauria, Plesiosauria and Metriorhynchidae according to palaeolatitude.