Argentinopachycephalosaurus

Argentinopachycephalosaurus is an extinct species of dinosaur part of the extinct group of bird-hipped dinosaurs, Pachycephalosaurids. It has the longest name of any named dinosaur, its name means Argentine Pachycephalosaurus. It resembled a North American Pachycephalosaurid, Stygimoloch (which may be a juvenile Pachycephalosaurus instead), but unlike Stygimoloch, Argentinopachycephalosaurus was indeed a fully-grown adult as the inside of their bones confirmed. It was the only known species of Pachycephalosaurid known indefinitely from South America, living in what is now Argentina during the Late Cretaceous from 72 million years ago to 66 million years ago. They were most likely completely herbivorous, but some scientists suggested that Argentinopachycephalosaurus could have been omnivorous, not only feeding on plants, but also on smaller animals and carrion during times of hardship. It is unknown why the Argentinopachycephalosaurus had became extinct.