What is "probrachylophosaurus"

Probrachylophosaurus bergei is a species of large herbivorous brachylophosaurin hadrosaurid dinosaur known from the Late Cretaceous Campanian Judith River Formation, of Montana.

The significance of this particular hadrosaur taxon is that it is a transitional species between the genera Acristavus and Brachylophosaurus evolving from a crestless ancestor (the former genus) to its crested descendant (the latter genus) while changing the morphology of its nasal bones.