A newly identified dinosaur species has been officially added to the family tree, thanks to fresh analysis of fossils first found more than a century ago.
An international team, including biologist D. Edward Malinzak from Penn State Lehigh Valley, has discovered that a 75-million-year-old fossil long thought to belong to a known dinosaur was actually a species of its own.
The new species has been named Ahshiselsaurus wimani, honoring the region of New Mexico where the bones were first uncovered in 1916. The findings were published in the Bulletin of the New Mexico Museum of Natural History and Science.
The fossil belongs to the duck-billed dinosaur family known as hadrosaurids, a group of large plant-eaters that thrived in western
North America during the Late Cretaceous. Although these dinosaurs are well studied and widely represented in fossil collections, many specimens discovered in the early 1900s were assigned to species before modern scientific tools existed.
This new study shows just how much those early classifications can change with a closer look.
The research team carefully reexamined the fossil bones—an incomplete skull along with pieces such as the right jugal, quadrate, dentary, surangular, and several neck vertebrae. These remains form the holotype, the specimen used to define a new species.
Originally, paleontologists had grouped this fossil with Kritosaurus, a well-known duck-billed dinosaur. But Malinzak and his colleagues found that the bones showed distinctive features that did not match Kritosaurus or any other known hadrosaurid.
According to lead author Sebastian Dalman of Montana State University, skull differences are the strongest basis for identifying a new dinosaur.
Even subtle variations in shape can signal that an animal belongs to a completely different species. In this case, the skull elements of Ahshiselsaurus wimani were unique enough to justify a new name and place on the dinosaur family tree.
The team also conducted a phylogenetic analysis, a method that compares physical traits to determine evolutionary relationships.
Their findings suggest that this new dinosaur was part of a larger pattern of migration across ancient North and South America. Malinzak explained that the American Southwest appears to have served as a starting point for groups of dinosaurs that spread northward into Canada and southward into Central and South America.
This movement likely reflects environmental changes that allowed new species to spread, thrive and sometimes replace older groups.
Interestingly, Ahshiselsaurus wimani appears in deeper rock layers than Kritosaurus, suggesting it is older than the species it was once confused with. That detail adds to growing evidence that the Southwest supported a rich, changing ecosystem where different dinosaur groups coexisted and evolved over time.
Malinzak has brought the methods from this research into his classroom, allowing students at Penn State Lehigh Valley to work directly with real-world scientific tools used to study evolutionary history. His colleagues praise the discovery as an example of how careful, detailed scholarship can reshape long-held assumptions.
The research team plans to continue studying the new species and reexamining other fossils from the region. Many specimens collected a century ago were identified quickly and stored away, and modern methods may reveal more hidden species.
Malinzak says the work is far from finished. Every new discovery answers some questions, but it also raises new ones. Understanding how these dinosaurs lived, migrated and adapted will take many more years of study.
As he puts it, the research journey is “not the end result—it’s just one lap in a much longer race.”
