(CNN)A group of 13 dinosaurs that died in a mud pit in China has yielded an unprecedented discovery. The 154 million-year-old limusaurus had tiny, sharp teeth as a hatchling that it gradually lost as it grew up, according to new research published in the journal Current Biology on Thursday. Read more: http://www.cnn.com/2016/12/22/health/dinosaurs-that-lose-teeth-china-trnd/index.html