Introduction
Welcome to Paleonews, where we cover all things dinosaur and paleontology related! This week we will cover two exciting discoveries- a new Pachycephalosauroid, as well as a species of Megaraptorid with a shocking discovery found in its mouth!
Zavacephale Rinpoche- September 17, 2025
Overview
A new species of pachycephalosaurid was recently discovered in Mongolia. Scientists have named it Zavacephale Rinpoche, and it stood about three feet and weighed only about 20 pounds, considerably less than the namesake of this group, Pachycephalosaurus, which was about 15 feet long and weighed over 600 pounds. Pachycephalosaurs are typically known for their thick, dome-shaped skulls and a bipedal stance, and include many famous dinosaurs such as Stygimoloch and Pachycephalosaurus. This group diverged from the bird-hipped dinosaurs, also known as the Ornothicians, which is a group that includes the Ceratopsians and Hadrosaurs.
What makes this discovery so special?
This discovery is groundbreaking, and paleontologist David Evans at the Royal Ontario Museum says “For those of us who study dome-headed dinosaurs, Zavachephelae is the specimen we have all been waiting for.” What makes this discovery stand out so much from others is the age of this fossil and how incredibly complete the skeleton is, with many parts of the shoulders, limbs, hips, and tail being present. Zavacephale has an estimated age that is 15 million years older than the oldest known Pachycephalosaur fossils, around 108 million years ago in the Cretaceous period. Due to the age of Zavacephale, it provides a perfect window to how this fascinating group of dinosaurs evolved, and its near-perfect skeleton shows how others in this group may have looked like.
“Before Zavacephale, our record of Pachycephalosaurs was almost exclusively limited to their indestructible domes. With such scanty skeletons, we were left to wonder about basic aspects of their anatomy, like what their arms would have looked like and how their digestive system functioned,” says Dr. Lindsay Zanno, a scientist who co-authored new research into this dinosaur.
This group of dinosaurs is particularly hard to research due to the limited fossil material, so to many paleontologists, Zavacephale Rinpoche is certainly an exciting discovery, providing a clear view to answering many unanswered questions.
Joaquinraptor Casali- September 23, 2025
Overview
In 2019, researchers in Patagonia, Argentina, came across a 23-foot long Megaraptor that has been named Joaquinraptor, after the son of Dr. Ibiricu, a paleontologist on the team that discovered this dinosaur. This is one of the most complete species of Megaraptor, and it is estimated to have lived around 70-66 million years ago, right at the end of the Cretaceous period.
This group was previously only known by fragmentary remains, so Joaquinraptor was a breakthrough. This specimen was particularly prominent, as it was from the end of the Cretaceous period, proving Megaraptors were apex predators- right to the end of the Mesozoic. What’s even more shocking about this discovery, however, is the fact that this particular Joaquinraptor was found with its last meal inside its jaws.
Last Meal
Recent studies on this specimen shows that this dinosaur was buried with an unusual feature – its last meal was still lodged in its mouth! Joaquinraptor had an arm bone of an early crocodile, later believed to have belonged to Kostensuchus Atrox, which was found in similar rock layers dating back to a similar time as Joaquinraptor.
Now, many scientists have debated whether this is truly an example of a dinosaur buried with food in its mouth, or if the bones were moved there after the dinosaur died. It’s possible that rushing water moved Kostensuchus and Joaquinraptor’s bones together, but if that was the case, the fossil site would have been a jumbled mess. Instead, the crocodile arm bone sat perfectly inside Joaquinraptor’s mouth, further hinting that this is how the dinosaur died, and that the bones were not buried together by pure chance. Additionally, the “near-life” positioning of Joaquinraptor shows that the bones have been largely unaffected by flowing water, meaning that it is less likely that the croc bone was brought there by exterior factors, further proving that Joaquinraptor died with its last meal.
Other Traces of Food Found in Fossils
This discovery is very significant, as traces of a dinosaur’s diet preserved in fossil material is extremely rare. Some other examples of diets preserved in fossils include Baryonx Walkeri, which was discovered with fish bones and scales preserved where the stomach would have been. We can also determine what a dinosaur ate based on coprolite and regurgitalites, which are fossilized feces and vomit. Overall, the discovery of Joaquinraptor is fascinating, and helps paleontologists understand the lives of these animals just a little bit more.
Further Reading/Sources
The Megaraptor Had Giant Claws and an Appetite for Crocodilians – The New York Times
New megaraptor discovered—with its final meal still in its mouth | National Geographic
JANICE CUI
- JANICE CUI
