It lay in a museum for almost 20 years - and then it turned out what they really found
A skull bone found in New Mexico has now led to the identification of a new type of dinosaur that lived tens of millions of years ago. For years, the fossil went through several classifications, until a re-examination revealed that it belongs to a previously unidentified species.
The fossil that waited for almost 20 years: a skull bone found in the summer of 2005 in northwestern New Mexico turned out to be the remains of a predatory dinosaur that was not previously known as a separate genus. Researchers gave it the name Dineobellator robustus, and it lived in the area about 73 million years ago, at the end of the Cretaceous period.
The dinosaur belonged to the Troodontidae family, a group of predatory, bird-like dinosaurs that were considered relatively agile and were characterized, among other things, by a large brain relative to body size and developed eyes. According to estimates, the Dineobellator reached a length of about 2.4 to 3 meters and its weight ranged from 70 to 140 kilograms, making it one of the larger members of the family known to science.
However, the interesting story in this case begins long before the dinosaur received its new name. The only fossil known from it so far is an almost complete left frontal bone, part of the skull roof, found in the San Juan Basin in New Mexico. For years, researchers tried to understand who it belonged to, and the answer changed time and time again.
When the first description of the fossil was published in 2006, it was classified as a new species of Saurornitholestes, a predatory dinosaur from the Dromaeosauridae family, the group associated with "raptor"-like dinosaurs. Later, paleontologists began to doubt this identification, and in 2014 the fossil was moved to the Troodontidae family.
Even then, the debate did not end. Some researchers believed that it was a fossil that could not be defined as an independent species, while a study published earlier this year suggested assigning it to another dinosaur named Xenovenator, discovered in Mexico.
Now, Dr. Steven Jasinski and Robert Sullivan have re-examined the fossil and reached a different conclusion. According to them, the structure of the bone is different enough from that of Xenovenator and other troodontids, and therefore it is a separate genus. The study was published on August 3 in the journal Fossil Studies.
Small differences in bones can be very significant in paleontology, especially when it comes to animals known only from partial fossils. In this case, the researchers focused, among other things, on the structure of the frontal bone and its thickness, and concluded that the dinosaur belonged to a group of relatively large troodontids with a thick and strong skull.
The evolutionary analysis they performed placed Dineobellator alongside Xenovenator from Mexico and Albertavenator from Canada. However, instead of being particularly close to Xenovenator, as previously suggested, the researchers found that Dineobellator is on an earlier branch of the same group.
"New work like this illustrates how much dinosaur research continues to change as we re-examine what we thought we knew," said Dr. Anthony Fiorillo, executive director of the New Mexico Museum of Natural History and Science. According to him, the finding also highlights the important place of New Mexico in the global research of dinosaurs.
Dr. Jasinski said that the new identification helps to better understand the diversity of the Troodontidae family in North America in the late Cretaceous. "It helps us get a clearer picture of the diversity in this family, and expands our knowledge of the dinosaurs that once lived in New Mexico," he said. The area where the fossil was found is considered one of the most important sites for understanding the world of dinosaurs in southwestern North America. In the San Juan Basin, many species have been discovered over the years, and some of them look different from their relatives who lived at the same time in other parts of the continent.
Researchers believe that this may indicate that the world of dinosaurs in North America of the late Cretaceous was divided into more complex local ecosystems than previously thought. Different groups of dinosaurs showed connections to species from distant regions, while others seemed unique to the region where they lived.
Dineobellator lived a few million years before the great extinction event that occurred about 66 million years ago and led to the disappearance of non-avian dinosaurs. At the time it lived, North America looked very different from today, and large parts of it were separated by a wide inland sea.
The fact that all this information is learned at this stage from only one bone highlights how partial the knowledge about these ancient animals still is. Researchers will now try to identify additional fossils from the same area that may belong to Dineobellator, in the hope that one day it will be possible to reconstruct its appearance and lifestyle more accurately.
