Illustration by Stephanie Abramowicz, Dinosaur Institute, Natural History Museum of Los Angeles County

ScienceShot: Rapid Evolution for Ancient Sea Monsters

One of the ancient world's most ferocious marine predators was a much stronger swimmer than scientists previously believed. Mosasaurs, reptiles up to 17 meters long, ruled the oceans 85 million years ago. Paleontologists used to think that one of the most common mosasaur genuses—Platecarpus—swam like eels, undulating their bodies back and forth. But another look at a complete fossil stored in the Natural History Museum of Los Angeles County made them think otherwise. Platecarpus actually swam like a shark, propelling itself forward using only its powerful tail, giving it an advantage over eel-like fish that have to move most of their bodies to get around. That means shark-like swimming evolved in the sea monsters 20 million years sooner than believed, the team reports online this week PLoS ONE today. Good for the predators; bad for anything unfortunate enough to be on the menu.

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