RESULTS

The ¹⁸O values for each bone of Giganotosaurus are shown in Figure 2. Intrabone and interbone temperature variability calculated from the isotope values are shown in Figure 3. The vertebrae have the lowest ¹⁸O values and thus represent the warmest skeletal elements. The cervical and dorsal centra show ~0.6‰ isotopic variability which corresponds to a 2.5°C intrabone temperature range. The caudal vertebrae have greater isotopic heterogeneities, ranging between 0.5-1.2‰ (2.5-5.0°C). There is less than 0.2‰ interbone isotopic difference between all of the vertebral centra, representing very little mean temperature differences between the vertebrae (<1°C). The neural spine of one cervical vertebra is ~0.5‰ more positive (~2°C cooler) than that of its associated centrum. The neural spine also has a slightly greater isotopic heterogeneity. Thus, while the caudal 4 vertebra exhibits the most negative mean value, there is no significant difference in temperatures (±0.3°C) for the vertebral centra. The ribs have higher ¹⁸O values with more intrabone variability than the vertebrae, including the neural spine. The two ribs sampled are between 2.5-3.0°C cooler than the vertebrae and intrabone temperature variability is ~3-4°C with no difference between ribs from the anterior and middle sections of the rib cage. Gastralia show a nearly 6°C intrabone temperature range. There is no apparent difference in mean temperature or variability between the proximal and distal ends of the rib from near the middle of the rib cage. The limbs show greater isotopic variability than the ribs. The femur displays 2-4°C intrabone temperature variability with no difference between the proximal and distal ends of the shaft, and displays a mean temperature over 3.5°C colder than the vertebrae. The tibia is 4-5°C cooler than the vertebrae and is coldest at its distal end. Heterogeneity in the ¹⁸O values suggests an increase in temperature variability from the proximal to distal end of the shaft of 3.5 to 4.5°C. Pubis mean temperatures remained between 2.5-3.5°C cooler than the vertebrae with intrabone temperature variability of 2-5°C.