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Tracy L. Ford wrote on 05/23/2002:

No specimen that has a boss, not just Pachyrhinosaurus, shows ANY evidence of a horn. The Pipestone Creek specimens have both Concave and Convex bosses. There are juveniles that have a rudimentary horn (or more properly, a split ridge) and at least one specimen that has both a ridge and the starting of a boss. It's a misinterpretation that ALL ceratopians had a nasal horn. Zuniceratops lacks one all together and there may be some later ones that also did.

Regarding this topic (among other things) there was a report in the December 1997 edition of the Earth magazine named "Horns of plenty". It was written by James Kirkland and centered on ceratopsids. Unluckily Earth magazine ceased to exist one year later :-(.


Heinz Peter Bredow

Excerpt from "Horns of plenty":

As its many well preserved fossils show Pachyrhinosaurus was a superlative beast. It was the biggest centrosaur, the last to die out, and the most far flung.

A Pachyrhinosaurus skull has been discovered on the North Slope of Alaska -- 350 miles from the position, at the time the animal lived, of the geographic north pole.

Perhaps most unusual of all is what Pachyrhinosaurus lacked: a horn.Young pachyrhinosaurs had small, bladelike nasal horns, but those crumbled away as the animals grew up, leaving adults with a massive rough boss, or buttress of bone, covering the top of the skull. In living animals the boss probably was capped by a knob of keratin, the same protein that makes up hair and fingernails.

Some paleontologists, however, suspect the "knob" of keratin may have been a spike - possibly a big one. Rhinoceros horns, they point out, are made of keratin anchored in bony bosses on the animals' skulls. No such horn has ever been identified from a centrosaur, but keratin from beaks and claws of other dinoosaurs has been discovered, and fossil-hunters are keeping their eyes peeled.