Researchers have discovered a species of duckbilled dinosaur that prowled the earth some 79 million years ago.
The discovery helps explain an evolutionary transition from an earlier duckbilled species to that group's descendants, according to the researchers.
The dinosaur named Probrachylophosaurus bergei is a previously missing link between a preceding species, Acristavus, which lived about 81 million years ago, and later form Brachylophosaurus, which lived about 77.5 million years ago, the study said.
"Probrachylophosaurus is 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," said Elizabeth Freedman Fowler, adjunct professor at Montana State University in the US.
"It is a perfect example of evolution within a single lineage of dinosaurs over millions of years," Freedman Fowler, who first uncovered and documented the species, said.
Their findings highlight how the new species of duckbilled dinosaur neatly fills a gap that had existed between an ancestral form with no crest and a descendant with a larger crest, providing key insight into the evolution of elaborate display structures in these gigantic extinct herbivores.
"The crest of Probrachylophosaurus is small and triangular, and would have only poked up a little bit on the top of the head, above the eyes," Freedman Fowler explained.
The other bones in its skull are very similar to those of Acristavus and Brachylophosaurus, Freedman Fowler said.
The analysis is based on specimens resulting from the fieldwork in the Judith River Formation in Montana.
The discovery was detailed in the journal PLOS ONE.
