Fossil teeth show how a mass extinction scrambled shark evolution
The dinosaur-destroying event flipped which sharks were most dominant in the oceans
![lemon shark underwater](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2018/08/080118_CG_shark-brief_feat.jpg?fit=860%2C460&ssl=1)
SHARK TALE After a mass extinction event about 66 million years ago, a group of sharks called carcharhiniformes, which includes the lemon shark (shown), became more abundant.
Doug Finney/flickr.com (CC BY-NC 2.0)