Mosasaurs used slam-start sneak attacks on prey

Mosasaurs are already terrifying enough. The Cretaceous marine reptiles were apex predators, with some species like Mosasaurus hoffmanii reaching nearly 50 feet long and weighing as much as 20,000 pounds. But a new study in Current Biology suggests some of them were even scarier: they used speedy, "slam-start" sneak attacks to take down prey.

Evolutionary paleontologist Kiersten Formoso at Rutgers University and her colleagues focused on four types of mosasaurs, including the massive Tylosaurus. That nearly 10-ton carnivore lived about 92 to 66 million years ago and grew to almost 45 feet long. Based on its anatomy and basic physics, Formoso says Tylosaurus likely ambushed prey with a single, powerful sweep of its tail, launching it as fast as 15 miles per hour toward an unsuspecting target.

"Physics is physics," said Formoso.

Tylosaurus and its close relatives had tails with a longer, more flexible portion that provided extra sweeping action. Formoso compared the attack to a swimmer pushing off a pool wall with legs and feet.

"It's the tail itself pushing off the water," she explained.

Of the four species examined, Mosasaurus and Plotosaurus probably preferred maintaining a steady speed in open ocean, while Platecarpus and Tylosaurus relied on slam-start ambushes in shallower water. That doesn't mean Plotosaurus was slow, Formoso clarified: its tail was built more for sustained, tuna-like swimming than for sudden bursts.

The team's theory is supported by existing knowledge of mosasaur fossil composition, tooth wear and estimated bite forces. Their data and tools are available free online so other researchers can examine other extinct marine species.

"At the same time dinosaurs like T. rex were ruling the land, mosasaurs were ruling the seas," said Formoso.