In a groundbreaking discovery in southern Mongolia, paleontologists unearthed the most complete and oldest fossil of a dome-headed dinosaur, Zavacephale rinpoche, dating back approximately 108 million years to the early Cretaceous period.

This find is particularly significant because it is the first definitive pachycephalosaur fossil from the early Cretaceous, pushing back the known timeline of this group's evolution by about 15 million years and filling a crucial gap in their early development.

The discovery was made in June 2019 by paleontologist Chinzorig Tsogtbaatar and colleagues, who identified the well-preserved skull as a new species, Zavacephale rinpoche, with the name highlighting its distinctive appearance and importance.

The fossil was found in a prehistoric lake valley alongside fossils of turtles, fish, and other herbivorous dinosaurs, indicating a diverse ecosystem during that period.

The juvenile fossil, about one meter long and weighing under six kilograms, provides detailed insights into early pachycephalosaur life, showing that even young Zavacephale had a fully developed dome.

The presence of a fully formed dome in juvenile specimens suggests that social behaviors, such as head-butting for territory or mates, were present early in the species' development.

Zavacephale's skull features a dome formed from a single bone with small spikes and bumps, indicating early development of features seen in later species.

This discovery significantly enhances our understanding of dome-headed dinosaur evolution, especially regarding cranial dome development, arms, and digestion.

Scientists are exploring the purpose of the thick skull domes, with hypotheses proposing they were used for socio-sexual displays and head-butting, similar to behaviors observed in modern animals like bighorn sheep.

The complete skeleton, the most complete ever found for a pachycephalosaur, reveals that Zavacephale was about the size of a German shepherd, with most of its body being lightweight, and it was at least two years old at death.

The name Zavacephale combines Tibetan for 'head,' emphasizing its role as the earliest known member of its group.

Published in the journal Nature, this discovery offers new insights into the anatomy and behavior of pachycephalosaurs, with the specimen's exceptional preservation likely leading to new hypotheses about their lifestyle and social interactions.