Mosasaurs were large marine reptiles that lived in the Late Cretaceous period, approximately 100 million to 66 million years ago. Celina Suarez, Alberto Perez-Huerta, and T. Lynn Harrell Jr. examined oxygen-18 isotopes in mosaaur tooth enamel in order to calculate likely mosaaur body temperatures and determined that mosaurs were endothermic--that is, they used internal metabolic processes to maintain a stable body temperature in a variety of ambient temperatures. Suarez, Perez-Huerta, and Harrell claim that endothermy would have enabled mosaurs to include relatively cold polar waters in their range.

Which finding, if true, would most directly support Suarez, Perez-Huerta, and Harrell's claim?

Question

Mosasaurs were large marine reptiles that lived in the Late Cretaceous period, approximately 100 million to 66 million years ago. Celina Suarez, Alberto Perez-Huerta, and T. Lynn Harrell Jr. examined oxygen-18 isotopes in mosaaur tooth enamel in order to calculate likely mosaaur body temperatures and determined that mosaurs were endothermic--that is, they used internal metabolic processes to maintain a stable body temperature in a variety of ambient temperatures. Suarez, Perez-Huerta, and Harrell claim that endothermy would have enabled mosaurs to include relatively cold polar waters in their range.

Which finding, if true, would most directly support Suarez, Perez-Huerta, and Harrell's claim?

Accepted Answer

Several mosaaur fossils have been found in regions known to be near the poles during the Late Cretaceous, while relatively few fossils of nonendothermic marine reptiles have been found in those locations.

Answer

Mosasaurs' likely body temperatures are easier to determine from tooth enamel oxygen-18 isotope data than the body temperatures of nonendothermic Late Cretaceous marine reptiles are.

Answer

Fossils of both mosaurs and nonendothermic marine reptiles have been found in roughly equal numbers in regions known to be near the poles during the Late Cretaceous, though in lower concentrations than elsewhere.

Answer

During the Late Cretaceous, seawater temperatures were likely higher throughout mosaurs' range, including near the poles, than seawater temperatures at those same latitudes are today.