Deciduous horn?

["Pat Grant (Library: Serials Catalog" <patg@vax2.concordia.ca>]

Is it at all plausible that the nasal horn of Triceratops might have been 
deciduous?  I realize it would be very weird indeed to have deciduous and 
non-deciduous on the same head, but haven't encountered any satisfactory 
explanation of why the nasal horn varies so drastically, from the 
rounded- basal- knob style, through the cute- little- rosebud- stuck- on- 
the- knob, to the huge mean vicious full-blown pointy horn as in the 
famous YPM 1922 T. prorsus.  Even if there is some sort of differential 
preservation involved, one wonders why it is so frequently the nasal horn 
that disappears.  Or is there a perfectly good explanation that I've 
somehow overlooked?

Pat
patg@vax2.concordia.ca