March 5, 2007—Its forehead sprouted horns as large as human arms, and its skull was frilled with spikes the size of sharks' teeth.

Even to the scientists who discovered this new species of dinosaur, the fearsome-looking creature was a bizarre sight.

But its weird appearance is what helped experts peg the dino as a missing link, a never-before-seen member from the family tree of Triceratops.

Dubbed Albertaceratops nesmoi, the 78-million-year-old dinosaur was unearthed in 2001 by paleontologist Michel Ryan and a colleague in the badlands of southern Alberta, Canada.

Ryan was initially puzzled by the animal's skull, he said, because it had the familiar giant horns of Triceratops but the ornate frill of another kind of ceratops called a centrosaur.

"We knew that we had something special that we had never seen before," said Ryan, now a curator at the Cleveland Museum of Natural History, in a statement.

"It meant that while Triceratops had giant horns, some centrosaurs did, too."

This odd combination of features suggests that Albertaceratops is the most primitive of the centrosaurs, Ryan explained, dating back to before centrosaurs split with the family that includes Triceratops.

"Unquestionably, it's an important find," Peter Dodson, a University of Pennsylvania paleontologist, told the Cleveland Plain Dealer.

"It was sort of the grandfather or great-uncle of the really diverse horned dinosaurs that came after it."

—Blake de Pastino

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