Paleontologists have found the fossilized remains of the oldest dome-headed dinosaur ever discovered.
The skeleton, found in the Khuren Dukh locality of the Eastern Gobi Basin in Mongolia, belongs to a new species of pachycephalosaur called Zavacephale rinpoche and dates back 108 million to 115 million years ago, according to a paper published in Nature on Wednesday.
The fossils are the most complete and oldest-known ever associated with a pachycephalosaur, known for their uniquely shaped heads.
“This specimen is a once-in-a-lifetime discovery,” said Lindsay Zanno, associate research professor at North Carolina State University and co-author of the paper, in a statement. “It is remarkable for being the oldest definitive pachycephalosaur, pushing back the fossil record of this group by at least 15 million years, but also because of how complete and well-preserved it is.”
Zavacephale skull.
North Carolina Museum of Natural Sciences
During its life, the Gobi Desert was a valley dotted with lakes and surrounded by cliffs or escarpments, the researchers said.
The newly discovered remains likely belonged to a small “teenaged” juvenile, measuring about 3 feet long and weighing nearly 13 pounds, said Tsogtbaatar Chinzorig, a paleontologist at the Mongolian Academy of Sciences who found the fossils and lead author of the paper, in a statement. It had a well-developed dome, suggesting it was sexually mature.
Pachycephalosaurs are often depicted using their domed heads to engage in headbutting duels.
The thickened skulls found on pachycephalosaurs are thought to have either provided a means for self defense or played a role in sociosexual behavior — to attract a mate or fend off competition, scientists said. Pachycephalosaurs were known for their complex sociosexual systems, the researchers said.
“If you need to headbutt yourself into a relationship, it’s a good idea to start rehearsing early,” Zanno said.
Artist’s reconstrution of the pachycephalosaur.
Masaya Hattori
Domed-headed pachycephalosaurs are among the “most enigmatic” dinosaurs, according to the paper.
“Pachycephalosaurs are iconic dinosaurs, but they’re also rare and mysterious,” Zanno said.
Z.rinpoche is one of the earliest diverging pachycephalosaurians — with its discovery pushing back fossil evidence of the frontoparietal dome by at least 14 million years, the researchers said.
The discovery fills a gap in the fossil record from the early Cretaceous period in Mongolia, according to the paper. The absence of early records impeded efforts to determine the origins and early evolution of the dinosaur species with dome-shaped heads.
“Z. rinpoche is an important specimen for understanding the cranial dome development of pachycephalosaurs, which has been debated for a long time due to the absence of early diverging or pre-Late Cretaceous species and the fragmentary nature of nearly all pachycephalosaurian fossils,” Chinzorig said.
