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Re: Play and spikes

John Bois wrote: 

> In most (all?) species that play, the play behavior usually relates to a 
> skill or behavior that the organism will need in adult life.  I forget 
> what wise person said it, but play is the _business_ of children.  I am 

It's exactly this that I find difficult to swallow.....it seems a cart before 
the horse kind of explanation. 

In order to kill prey, for example, you don't need to practice as a youngster. 
Plenty of species get by without. 

We say that calves "play" at escape tactics, or at courtship rituals,
or whatever, but their adult courtship behaviour is for example, no
more complex than that of, say, spider courtship. So it seems to me to
give "play" a "usefulness" factor is just wishful thinking for
something we observe but cannot find a justification for. And so we
attribute it to "more intelligent" animals.  I don't see crows taking
over the birdy world and geese suffering because of it.  I therefore
hold it has no real value, and was probably unnecessary for dinos, as
it still is for a lot of species.

Mark Sumner wrote:

> almost two meters above the ground (or more).  Unless we make 
> the assumption that all predators of _S. stenops_ were both 
> taller, and always attacked from above. Otherwise, all the 
> upper armor was for naught.

So far we have (if I read aright) no evidence of a firmly fixed plate;
they are just overblown scutes embedded in the skin (whether standing
up or laying flat).  Now, the problem with this is that you have a
large mass attached by a (relatively) weak attachment. It would surely
not take much (relatively) leverage to tear the off, and I would have
thought (no calculation) any respectable size tyrannosaur could have
done it (some one must have studied jaw strength etc).  So, could they
really have been much use as armour? I think not. Therefore the tails
spikes must play a very important defensive role, and I could envisage
a S. stenops turning tail toward an aggressor and waving his spikes
around in a threatening way; maybe even raising it up to cover his