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Re: Defense



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 
a herd.

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 
simple, 
> 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?

Cheers

Heinz Peter Bredow