Too big in overall size, or longer? If longer it might just be less worn, or like you say, it could be another ornithischian. But I don't think we have a good handle on tooth variation between different species within a family yet. If it's previously undocumented, it may not perfectly match.

Either way, it's a new record for the "Mesaverde" in Wyoming, so it's an important specimen!

Absolutely! And ontogenetic variation, too....I wonder this often with theropod teeth. (and I'll have to ask him to clarify on the size thing for denticles)