Mosasaurs were large marine reptiles that lived in the Late Cretaceous period, approximately 100 million to 66 million years ago.Celina Suarez, Alberto Pérez Huerta and T. Lynn Harrell ]: examined oxygen-18 isotopes in mosasaur tooth enamel in order to calculate likely mosasaur body temperatures and determined that mosasaurs were endothermic-that is, they used internal metabolic processes to maintain a stable body temperature in a variety of ambient temperatures. Suarez Pérez-Huerta, and Harrell claim that endothermy would have enabled mosasaurs to include relatively cold polar waters in their range. Which finding, if true would most directly support Suarez, Perez-Muerta, and Marrelly claim? A Mosasaury likely body temperatures are easier to determine from tooth enamel oxygen-1Sisotope data than the body temperatures of A nonendothermic late Cretaceous marrine reptiles are. D Fossils of boti mosasaurs and nonendothermic marine repties have been foundin roughly equal numbers in regions known to be near the poles during the Late Cretaceous, though in lower concentrations than elsewhere. C Several mosasar fossils have been found in regions known to be near the poles during the Late Cretaceous, while relatively few fossils of C noner idothermic maxine reptiles have been found in those locations. D Daring the Late Cretaceous seawater temperatures were likely higher throughout mosasaurs' range, includingnear the poles, than seawater temperatures at those same latitudes are today.

## Step 1<br />The problem is asking us to identify which finding would most directly support the claim that mosasaurs were endothermic, meaning they used internal metabolic processes to maintain a stable body temperature in a variety of ambient temperatures. <br /><br />## Step 2<br />Option A talks about the ease of determining mosasaur body temperatures from tooth enamel oxygen-18 isotope data compared to nonendothermic marine reptiles. This doesn't provide evidence for endothermy; it only discusses the methodology.<br /><br />## Step 3<br />Option B states that both mosasaurs and nonendothermic marine reptiles have been found in roughly equal numbers in polar regions. This doesn't support the claim of endothermy, as it suggests that both types of reptiles could survive in cold environments.<br /><br />## Step 4<br />Option C mentions that several mosasaur fossils have been found near the poles, while relatively few nonendothermic marine reptiles have been found in those locations. This suggests that mosasaurs, which were endothermic, could survive in colder environments compared to nonendothermic reptiles. This option supports the claim of endothermy.<br /><br />## Step 5<br />Option D discusses the likely higher seawater temperatures during the Late Cretaceous near the poles. This doesn't provide evidence for mosasaurs' endothermy; it only provides information about seawater temperatures.<br /><br />## Step 6<br />Based on the analysis, the finding that would most directly support the claim of mosasaurs being endothermic is option C.