CRETACEOUS CRUISE CONTROL: SETTING THE PACE FOR MOSASAURS

Marine reptiles that flourished throughout the Mesozoic showcase key adaptations to aquatic locomotion, including fusiform torsos and paddle-like limbs. We consider hydrodynamic consequences of the mosasaurid body plan, with special attention to the relationship between overall size and locomotory efficiency. Size and distribution of mosasaurid fossils, particularly across the Western Interior of North America, suggest these animals occupied large territories and may have traversed great distances during their lifespans. We produce a range of mosasaurid soft-body reconstructions and compare their hydrodynamic costs and advantages using simulations of computational fluid dynamics. Instead of estimating the animal’s top speed or likely attack strategy, we attempt to estimate the most efficient velocity at which these animals could traverse several kilometers of ocean habitat. We speculate that mosasaurids may have used intermittent fluke-propelled swimming to maintain a low but persistent velocity when traveling long distances. Second-order flow features suggest that the paddles would best serve as cruise control (forelimbs) and roll prevention (hindlimbs). These results illuminate features of marine tetrapods that recur as themes throughout geologic time, as well as those that are most iconically linked to the mosasaurids specifically.