A fossil unearthed in New Mexico more than 100 years ago was the largest duck-billed dinosaur ever seen.

Scientists have discovered a giant type of duck-billed dinosaur that lived in what is now New Mexico about 75 million years ago.

The dinosaur Athisresaurus wimani probably had a flattened head and a bony crest low on its snout, researchers found in a study. The findings, to be published in the Proceedings of the New Mexico Museum of Natural History and Science, suggest that during the last 20 million years of the Cretaceous Period (145 million to 66 million years ago), platypus dinosaurs, or hadrosaurs, may have been more diverse and duplicated than previously thought.

Hadrosaurs were large plant-eating dinosaurs that lived during the last 24 million years of the Cretaceous period. They are “sometimes colorfully referred to as ‘Cretaceous cows,'” study co-author Stephen Jasinski, a paleontologist at the Harrisburg College of Science and Technology in Pennsylvania, said in a statement. “It may not be a perfect metaphor, but they probably lived in groups and were prominent in the environment of northern New Mexico near the end of the Cretaceous period.”

you may like

A. wimani could have grown up to 40 feet (12 meters) long, the statement said.

One set of A. wimani fossils, discovered in 1916, had previously been identified as a member of the hadrosaurid genus Kritosaurus. However, existing fossil specimens are frequently reevaluated as more data and fossils become available.

In the new study, researchers reexamined a series of fossils from the Kirtland Formation in New Mexico, including an incomplete skull, a lower jaw bone, and several vertebrae. The fossil was kept at the Smithsonian National Museum of Natural History.

Anthony Fiorillo, study co-author and executive director of the New Mexico Museum of Natural History and Science, said in a separate statement that “as a general principle, the skull is the real basis for distinguishing between animals.” “When you have a skull and you notice a difference, that carries more weight than, say, if you found a toe bone that looked different.”

By comparing the skull to those of other hadrosaurids, the researchers found that its shape and features were sufficiently different from those of other hadrosaurids that it likely belonged to a different species. A. wimani is closely related to Kritosaurus, suggesting that their evolutionary lineages did not diverge that long ago.

“Kritosaurus remains a valid genus with its own species,” study co-author Edward Marinczak, a paleontologist at Penn State Lehigh Valley, said in a second statement. “We took specimens that were lumped together as individual Kritosaurus and determined that they had very different anatomical features that ensured that it was its own genus and species.”

The researchers write in their study that it is still unclear how closely related species coexisted in the same environment. But tracking the history and range of different species can help scientists understand the environments they lived in and the evolutionary history of duck-billed dinosaurs.

“It appears that these strains coexisted in this area for a time,” Marinczak said. “We show that this group not only exploded in diversity across the continent at one point, but also contributed to the global spread of this group during the Late Cretaceous.”