ANDREW LIMBONG, HOST:
The pachycephalosaurs were a unique group of dinosaurs with domed heads, but scientists haven't known much about them because their fossils have been so incomplete until now. Science reporter Ari Daniel describes a stunning discovery from southern Mongolia.
ARI DANIEL, BYLINE: It was a cloudy morning in June 2019, when paleontologist Chinzorig Tsogtbaatar and several colleagues set out by foot from their campsite to a rocky outcrop dating back about 110 million years to the early Cretaceous.
CHINZORIG TSOGTBAATAR: Then after 15 to 20 minutes, I saw something in other side of the hill.
DANIEL: A bright object of some sort.
TSOGTBAATAR: It wasn't looked like a frog - very unusual. Then I want to go down to check.
DANIEL: Once he got closer, Tsogtbaatar, who now works at North Carolina State University, knew exactly what it was.
TSOGTBAATAR: It was a skull.
DANIEL: And not just any skull. It was dome shaped. Tsogtbaatar had just discovered a new species of pachycephalosaur.
TSOGTBAATAR: We just stopped breathing.
LINDSAY ZANNO: So this is the first definitive pachycephalosaur that's ever been found in the early Cretaceous.
DANIEL: Meaning it's 15 million years older than what had been the oldest pachycephalosaur, says Lindsay Zanno, also a paleontologist at NC State. This specimen fills in a crucial gap in the early evolution of this group of dinos. Zanno remembers the moment she first laid eyes on it.
ZANNO: I mean, everyone just stood around the lab just holding this precious, incredible skull. Everyone is enchanted. It's just the most beautiful specimen.
DANIEL: That domed head made of solid bone and edged in spikes is any pachycephalosaur's most distinguishing feature.
ZANNO: Their domes are essentially indestructible. It would have been able to protect the skull against pressure or impact. And so we think that these animals were battling it out with their heads.
DANIEL: Still, researchers have known relatively little about these plant eaters. That's because most of the rest of their bodies haven't been found. So when the team in Mongolia went on to excavate dozens more bones from that new animal, it became the most complete pachycephalosaur skeleton ever to be unearthed.
ZANNO: It's about the size of a German shepherd. But you have to remember, 75% of the body is a neck and a tail, so they're very light, at about 12 pounds.
DANIEL: This little fossil has already revealed a couple insights. For instance, this was the first time the hand bones of a pachycephalosaur were found, and they were super small.
ZANNO: We thought it was something it ingested instead of parts of its own body. That's how tiny its hands were.
DANIEL: In addition, the limb bones allowed the researchers to age the dinosaur. It was at least 2 years old, a juvenile, meaning that young pachycephalosaurs like this one already had a fully developed dome.
ZANNO: Whether they were battling it out for territory or mates is something we're not entirely sure of, but whatever they were doing with those domes, they started practicing at a very young age.
DANIEL: The research is published in the journal Nature. Cary Woodruff is the curator of vertebrate paleontology at the Frost Museum of Science in Miami and wasn't involved in the discovery. He says usually, paleontologists have to work with very incomplete skeletons.
CARY WOODRUFF: In our mind, we can see, we can imagine, like, what the rest of it looked like. But you didn't have to imagine anything with a specimen like this. It was there, right? The teeth are literally smiling at you.
DANIEL: Woodruff is confident this fossil will spawn new ideas about how pachycephalosaurs once lived. Meanwhile, the specimen's back home in Mongolia, and the new species has a new scientific name that Chinzorig Tsogtbaatar bestowed.
TSOGTBAATAR: Zavacephale rinpoche.
DANIEL: That second word, rinpoche, is Tibetan for precious one and refers to the domed skull, which appeared out of the rock face to Tsogtbaatar like a perfectly polished jewel. For NPR News, I'm Ari Daniel.
(SOUNDBITE OF FOUR TET'S "AS SERIOUS AS YOUR LIFE") Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
