According to this Yahoo!News article, there’s a new evolutionary intermediate in town; Albertacertops nesmoi. For a long time, ceratopsians with a variety of horn shapes and sizes have been known, but it’s been difficult to pin down what groups gave rise to others. This newly discovered dinosaur appears to be the most basal of the centrasaurines, which would show that this group lost its horns over evolutionary time (later forms like Pachyrhinosaurus lacking large brow horns). It is curious that large horns were developed and then lost by some groups with the proliferation of the ceratopsians, some fossils that predate this new discovery by about 12 million years did have large horns as well, i.e. Zuniceratops. As more intermediates come to light it would be interesting to chart the development and loss of horns in these dinosaurs, and in a way, ceratopsians remind me of the duckbilled dinosaurs, having many different varieties of horns/crests but essentially the same body plans. In any event, this is indeed an important find. Quote Jim Kirkland about the find
Lo and behold, evolutionary theory actually works
As if there was any doubt. The abstract of the paper describing the placement of the species can be found here, the disctinctive brow-horns deemed a synapomorphy (even though this dinosaur and later ceratopsians have large horns, this dinosaur is not ancestral to Triceratops or members of other groups with similar horns), thus showing the loss of brow horns in a group that developed some other odd skull characters.