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Steve Brusette asked:
> Why would juveniles, the animals most vulnerable to predators, not
>possess these features if they were truly used for defense? Why would
>evolution leave the most vulnerable defenseless while the least vulnerable
>possess defense weapons?
Steve Jackson answered on 02/10/2001:
> Perhaps because it's the "job" of the adults to protect the young. There's
> a considerable metabolic investment in growing those horns and frills, and
> a little baby dino is still going to be an easy mouthful for a predator
> even if it DOES have defensive gear. One could speculate that the best
> investment of a young dinosaur's energy was to grow as quickly as possible,
> gaining some defense from size itself . . . and only then to develop
> weaponry, once it had the mass to use it effectively, on its own behalf and
> that of its offspring.
A new-born ceratopsian was without any of these horns and frills. And
development of these may have been postponed to keep aggression levels low in
And it is not proven that horns and frills were for defense.
>From an eMail to the DML (1998JAN/MSG00363.HTML "Centrosaur Ontogeny Paper")
> Juvenile and sub-adult centrosaurines are characterized by relatively
> unadorned frills compared to their adult counterparts. As in numerous
> living taxa, the cranial ornaments of centrosaurines developed late
> in ontogeny, as individuals approached or attained adult size.
> The late ontogenetic development and diverse taxonomic variation of horn
> and frill morphologies support the contention that these structures are best
> interpreted as reproductive characters employed in mate competition.
Personally I think that they were used for species recognition and display of
rank and defense. Why should a certain character used only for one purpose?
Heinz Peter Bredow