An entirely new species of dinosaur discovered in New Mexico adds a whole new dimension to our understanding of the age of the dinosaurs.
The dinosaur discovery came from 20 fossil skeleton fragments, uncovered in the Ojo Alamo Formation in the San Juan Basin, New Mexico. Together, the fossils reveal a species dromaeosaurid previously unknown to science: Dineobellator.
The fossils offer detailed insights into exactly what this feathered, carnivorous creature from 67 million years ago would have looked like. They also advance scientists' understanding of dinosaur evolution during that very Late Cretaceous period.
"I prefer to think of these fossils in a way that brings these animals back to life, thinking of them as real living, breather animals and not just bones," Steven Jasinski, a paleontologist from State Museum of Pennsylvania, and lead researcher on this study, tells Inverse.
"Here we were able to hypothesize about various aspects of its behavior, its appearance with feathers, and some of the unique events in this animals life that caused it to be injured," he says.
Curiously, the fossils also reveal this dinosaur had an injured rib that had healed.
"It also had a unique gouge and puncture on the hand claw, which is the same size as the tip of the claw, suggesting two Dineobellator got in a fight and one clawed the other one," Jasinski says, speculating it may have been a fight over resources or over a mate.
"All of this exciting information helps us visualize what this incredible animal may have been like in life."
"Not only can we picture [this dinosaur] 67 million years ago in northwestern New Mexico, but we can also understand more about this one individual's life."
The discovery is detailed in a study published Thursday in the journal Scientific Reports.
Meet Dineobellator notohesperus
Jasinsky and his colleagues dubbed the newly discovered dinosaur Dineobellator notohesperus.
The name comes from the Navajo word Diné, which means Navajo people, and the Latin word bellator, which means warrior. The notohesperus comes from the Greek noto, southern, and hesper, western.
Dineobellator is not just new to science — it also had several unique morphological features, including its size, muscle structure, and tail, which together made it an agile Cretaceous fighter unlike any other.
"Dineobellator would have been able to take down very large prey, especially if it hunted in packs," Jasinski tells Inverse.
"All of these things show an exciting, agile, adept predator."
According to the fossil measurements, Dineobellator was about the size of a wolf. It was likely 6-7 feet long and 3 feet tall, weighing about 40-50 pounds, according to Jasinski.
"Although it would have been longer than a wolf, but weighed less as it was a lightly built, swift predator," he says.
2. Muscular legs and arms
The fossil remains suggest the Dineobellator had strong, flexible arms, and the same goes for its hind legs, as a fossil fragment of the creature's right femur suggests.
Other muscular and skeletal traits caught researchers' attention, too, Mark Powers, a graduate student from University of Alberta's dinosaur lab, tells Inverse. Powers was not involved in the discovery.
"The presence of large deltapectoral crest of the humerus may indicate a greater use of the forelimb for handling prey," Powers says (that's a strong shoulder joint). But these features can vary quite widely among individuals, even within a species, he says, so it can't be taken as proof that all Dineobellator show the same feature.
"This is especially true for osteological features that are strained under muscular forces frequently as with the upper arm bone, the humerus," Powers says.
3. Clawing hands and feet
"Features of the hands and feet suggest it had a lot of strength to close them, in a kind of grasping or gripping action," Jasinski tells Inverse.
2. Stiff tail
This dino had a fairly stiff tail, reinforced with bones and tendons along it, the fossils suggest.
Jasinski explains that these features allowed the tail to remain stiff and straight as the dinosaur moved around, essentially acting like a rudder and helping them keep their balance when running at high speeds.
But the fossils also suggest that the Dineobellator's tail was highly mobile at its base, near the hips, and this likely made it even more agile.
"Think of a cheetah chasing a gazelle," Jasinski says.
"The cheetah's tail is held straight and balances the cat, but as the gazelle changes direction, the tail whips around, acting as a counter-balance and allowing fast changes of direction."
"The tail of Dineobellator could have been similar, acting as a counter-balance for fast changes of direction and better agility. This would have made Dineobellator a formidable predator."
But with no similar fossils of other late-Cretaceous dromaeosaurids to compare Dineobellator to, it is difficult to know if these features are truly distinct to this dinosaur specifically, Powers says.
Dineobellator's feathers weren't meant for flying. Instead, they were likely used for sexual selection or camouflage, according to the researchers.
The find is particularly important for paleontologists, as there is a sparse fossil record for Dromaeosaurids dinosaurs, especially for those that lived in their last days, during the Cretaceous-Paleogene periods. In fact, these fossil findings are the most complete theropod skeleton recovered from this type of dinosaur.
That, in itself, is a brilliant find, according to David Fastovsky, a paleontologist at the University of Rhode Island. Fastovsky was not involved in the study.
“Twenty identifiable specimens is a huge number; so depending upon the nature of the circumstances, the find itself could be quite compelling,” Fastovsky says.
According to Jasinski, the researchers had clues that there was probably some kind of dromaeosaurid living in the area, but they had no idea about the unique nature of the animal, its potentially weird behavioral characteristics, or its relationships.
"More specimens will probably reveal other surprising and exciting information, but the only way to do that is get back out in the field and find more fossils," Jasinski says.
Dino dynasties revealed
The Dineobellator may have been part of the same family as velociraptors.
“[Velociraptor] were, pound for pound, the most fearsome carnivorous dinosaurs that ever lived, including Tyrannosaurus and its friends. So, having another New World dromaeosaur is a great thing,” Fastovsky says.
The findings also support the idea that there was an ancient, dinosaur migration from Asia to North America, he says.
Jasinski agrees. That this dinosaur is so closely related to other dromaeosaurids from Asia, it suggests its ancestors migrated from Asia to North America, and then evolved their unique features once they got there.
“I'm not sure that this is a ‘game-changing find,’ but it does reinforce this clear pattern that we've observed of Asian dinosaurs migrating to the New World, probably using the same land bridge that carried humans some 66 million years later,” Fastovsky says.
Importantly, the findings suggest that dromaeosaurid dinosaurs were still diversifying even until the very last moments of their existence — right before all non-avian dinosaurs were wiped off the face of the planet in a mass extinction 65.5 million years ago.
"Its unique features tell us these dinosaurs were still evolving new traits and trying out new things right until the end," Jasinski says.
"Rather than these dinosaurs being in sharp decline before the extinction, the mass extinction brought this unique evolutionary pathway to a catastrophic end."
"It gives us insight into a larger part of the ecosystem that T-Rex lived in than finding another skeleton of T-Rex would give us."
Corwin Sullivan, associate professor of Vertebrate Palaeontology at University of Alberta, tells Inverse that the new fossil is just the tip of the iceberg when it comes to understanding these delicate dinosaur dynamics.
"Apart from the search for more new species, it would be very helpful to find more complete fossils of the new dromaeosaurid, Dineobellator, and of the similarly fragmentary Acheroraptor from the Maastrichtian of Montana."
That will be the key to a more complete understanding of these animals and their place in the dromaeosaurid family tree, he says. Sullivan was not involved in the research.
"We have far more skeletons of large animals like T-Rex than we do of raptors from these rocks, whereas the dog-sized dinosaurs would have been much more common than the elephant sized ones," Philip Currie, professor of Dinosaur Palaeobiology at University of Alberta, tells Inverse.
"When an an associated skeleton of an animal the size of Dineobellator is found, it gives us insight into a larger part of the ecosystem that T-Rex lived in than finding another skeleton of T-Rex would give us."
Abstract: Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the time of their extinction near the Cretaceous-Paleogene boundary. Here we report on a new dromaeosaurid, Dineobellator notohesperus, gen. and sp. nov., consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, the first diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southern United States (southern Laramidia). The holotype includes elements of the skull, axial, and appendicular skeleton. The specimen reveals a host of morphologies that shed light on new behavioral attributes for these feathered dinosaurs. Unique features on its forelimbs suggest greater strength capabilities in flexion than the normal dromaeosaurid condition, in conjunction with a relatively tighter grip strength in the manual claws. Aspects of the caudal vertebrae suggest greater movement near the tail base, aiding in agility and predation. Phylogenetic analysis places Dineobellator within Velociraptorinae. Its phylogenetic position, along with that of other Maastrichtian taxa (Acheroraptor and Dakotaraptor), suggests dromaeosaurids were still diversifying at the end of the Cretaceous. Furthermore, its recovery as a second North American Maastrichtian velociraptorine suggests vicariance of North American velociraptorines after a dispersal event during the Campanian-Maastrichtian from Asia. Features of Dineobellator also imply that dromaeosaurids were active predators that occupied discrete ecological niches while living in the shadow of Tyrannosaurus rex, until the end of the dinosaurs’ reign.