NEW SKELETONS OF CERATOPSID, HADROSAURID, AND TYRANNOSAURID DINOSAURS FROM THE UPPER CRETACEOUS MENEFEE FORMATION OF NEW MEXICO

An ongoing project conducted by the Western Science Center and Zuni Dinosaur Institute for Geosciences, assisted by volunteers from the Southwest Paleontological Society, has added to the previously sparse dinosaur record from the Upper Cretaceous Menefee Formation, San Juan Basin, New Mexico. Between 2011 and 2016, the project collected dinosaur material from numerous sites in the Allison Member of the Menefee Formation on U.S. Bureau of Land Management land. Although fragmentary, these finds led to the recognition of the new nodosaurid Invictarx zephyri and tyrannosaurid Dynamoterror dynastes in 2018.

More recent discoveries include three well-preserved associated dinosaur skeletons collected in 2017-2019. A medium-sized ceratopsid skeleton includes dorsal vertebrae and ribs, the sacrum, and an ilium. It is currently impossible to determine whether this specimen represents the same taxon as the centrosaurine ceratopsid skeleton reported by the New Mexico Museum of Natural History & Science in 1997.

A new genus and species of brachylophosaurin hadrosaurid is represented by a large partial skull and postcranium. The frontals exhibit a caudally expanded nasofrontal suture similar to those of the crested Probrachylophosaurus bergei and Brachylophosaurus canadensis from Montana and Alberta. This is the first brachylophosaurin reported from New Mexico.

The project has collected approximately 30 bones, including cranial elements, of a large tyrannosaurid. Study and preparation of this specimen is in the earliest stages, and it is not yet possible to ascertain whether it represents Dynamoterror dynastes.

The project’s discoveries demonstrate the potential for the Allison Member to illuminate a little-known slice of dinosaur evolution in Laramidia around 80-79 Ma. In addition to anatomical and systematic studies, future work will focus on the paleobiogeographic, biostratigraphic, paleoecological, and functional implications of these dinosaurs.