Ahshislesaurus: New Hadrosaurid from New Mexico That Lived Right Before the Asteroid Doom!

In a major 2025 paleontological breakthrough, scientists have named Ahshislesaurus wimani—a mᴀssive new flat-headed hadrosaurid from New Mexico’s Kirtland Formation that thrived around 75 million years ago, just millions of years before the Chicxulub asteroid wiped out non-avian dinosaurs.

Described in a Journal of Systematic Palaeontology paper by Sebastian G. Dalman and colleagues, the species was long misidentified as Kritosaurus. The holotype and referred specimens, collected from the lower Hunter Wash Member near the Ah-shi-sle-pah Wilderness, include skull elements and postcranial bones revealing a large duck-billed herbivore estimated at 11–12 meters long.

Its most distinctive trait is the flat skull with a low, broad snout—forming, together with Naashoibitosaurus, a potentially new clade of saurolophine hadrosaurids. These “flat-heads” appear specialized for a unique feeding strategy in the lush floodplains of Late Campanian North America.

The discovery is especially significant because Ahshislesaurus lived deep in the final chapter of dinosaur history, coexisting with Pentaceratops and other iconic taxa in the San Juan Basin. Its presence shows hadrosaur diversity remained high right up to the final few million years before the mᴀss extinction.

Experts hail the find as proof that the “duck-billed” dynasty was still evolving and thriving on the eve of doom. From the badlands of New Mexico, Ahshislesaurus wimani emerges as a vital missing piece—showing the last great wave of hadrosaur innovation before the asteroid struck. Paleontology’s final Cretaceous chapter just gained a thrilling new star!