pachycephalosaur

From scientific Latin Pachycephalosaurus.

pachycephalosaur (plural pachycephalosaurs)

1. Any of a group of herbivorous dinosaurs, of the genus Pachycephalosaurus from the late Cretaceous period. [from 20th c.]
   • 2016 September 28, David Hone, “‘Three-eyed’ extinct reptile was a bone-headed dinosaur mimic 100 million years early”, in The Guardian‎:

     One could almost call Triopticus a mimic were it not for the fact that it dates to 228-220 million years ago, meaning that it predates the pachycephalosaurs by over 100 million years.