A new duck-billed dinosaur (Probrachylophosaurus bergei) that sported a relatively short head crest – in comparison to its large-crested ancestors – was recently unearthed in Montana and may prove to be a long-sought evolutionary missing link.

Researchers from Montana State University concluded that Probrachylophosaurus is a member of the Brachylophosaurini clade of dinosaurs, which are known to have existed in North America during the Late Cretaceous period. The new fossils exhibited a small flat triangular bony crest extending over the skull, which suggests the specimen may represent the transition between non-crested ancestors, such as Acristavus, and the larger crests of Brachylophosaurus, according to MSU's news release.

Acristavus gagslarsoni, which lacked a nasal crest, roamed the Earth between 81 and 80 million years ago. Brachylophosaurus Canadensis, on the other hand, possessed a flat paddle-shaped nasal crest projecting back over the top of its skull and can be traced to 77.8 million years ago. 

Fossils of Probrachylophosaurus were originally excavated from the Judith River Formation in Montana and date to 79.8 and 79.5 million years ago. It didn't take long before researchers noticed that the fossilized bony triangular nasal crest fell between those of its non-crested and large-crested ancestors. 

"Probrachylophosaurus is therefore exciting because its age – 79 million years ago – is in between Acristavus and Brachylophosaurus, so we would predict that its skull and crest would be intermediate between these species. And it is," explained Elizabeth Freedman Fowler, the co-author of the study and a professor at Montana State University. 

"This part of the Judith River Formation represents a slice of time intermediate between areas where lots of dinosaur fossils have been collected in the past. The new species that we find here are 'missing links' between known dinosaur species, so it's a really exciting field area," Fowleradded in the university's release.  

The study was recently published in the journal PLOS ONE. 

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