Scientists have unearthed in Mongolia the oldest and most complete fossil of a pachycephalosaur, a group of dinosaurs known for their dome-shaped skulls, according to a new study published Wednesday in the journal Nature.

The fossil, which dates to 108 to 115 million years ago, is that of a juvenile from a previously unknown species that researchers are calling Zavacephale rinpoche.

It was discovered in the Khuren Dukh formation in the Gobi Desert in Mongolia, a landlocked country between China and Russia , by a team led by paleontologist Tsogtbaatar Chinzorig of the Mongolian Academy of Sciences.

Very little is known about pachycephalosaurs, two-legged herbivores that lived in Asia and North America during the Cretaceous period and are among the “most enigmatic” dinosaur

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