Mosasaurs May Have Used Breast Stroke to Ambush Prey

Posted on September 23, 2019

Mosasaur Breast Stroke

A new research study suggests mosasaurs used a muscular breast stroke that gave them an extra burst of speed. This speed may have been used when ambushing prey. Mosasaurs were huge late Cretaceous sea creatures that were also equipped with two rows of sharp teeth that could shred their victims apart.

Researchers from the University of Southern California focused on the oversized pectoral girdle as they studied a fossil of a Plotosaurus, a type of mosasaur, at the Natural History Museum of Los Angeles County. They determined that the mosasaurs' unusually large and low-placed pectoral girdle supported large muscle attachments. The researchers also say mosasaurs had asymmetry in the bone structure which they say is "a telltale sign of the strong, inward pull-down motion called adduction." The researchers determined that mosasaurs likely used their forelimbs to swim, breast-stroke style, adding powerful bursts of propulsion to their ability to cruise.

Kiersten Formoso, a Ph.D. student in vertebrate paleontology at USC and lead author of the study, says in a statement, "We know that mosasaurs most likely used their tails for locomotion. Now we think that they also used their forelimbs, or their tail and forelimbs together."

Mike Habib, Assistant Professor of Anatomical Sciences at USC, and study co-author says, "Like anything that swims or flies, the laws of fluid dynamics mean that burst versus cruising is a tradeoff. Not many animals are good at both."

Formoso says the dual swimming style of the mosasaur would make it unique among tetrapods, living or extinct. She says that what is for certain is that "Mosasaurs swam unlike anything else."

The research paper will be presented tomorrow at the Geological Society of America annual meeting in Phoenix, Arizona.

Here is some more information on mosasaurs from National Geographic:



Image: Restoration illustration of Plotosaurus bennisoni from Wikimedia Commons, CC BY 3.0.