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Re: Dinosaurs are not mammals



Tracy Ford writes;

>Have you seen any real or cast's of Ceratopian skulls? I've 
>seen dozen's of them. I've talked to paleontologist who specilize on 
>Ceratopians. The fenestra have NOTHING to do with jaw muscles. If the 
>frill had anything to do with the jaw muscles they would have broken 
>their frills because they are so lightly built.

I disagree with this claim, for two reasons: First, muscle load would
be transmitted along the entire edge of the fenestra (lengthening the
perimeter while keeping the same load).  This would reduce the amount
of stress applied to any one area, and allow for a lighter structure.

Secondly, it would seem that the load generated by chewing shouldn't
be all that massive.  Even for the toughest vegetation, a
slow/rhythmic motion of the jaw wouldn't produce critical stresses.  A
possible way to test this one way or another, is to measure the dental
battery and frill length, and see whether the dental battery becomes
larger as the frill becomes longer.

>Did you know that the top of the braincase isn't the top of the skull? 
>That there is a large sinus between what would normally be the top of 
>the skull and the actually top of the skull in ceratopians. Some 
>ceratopian's have a hole or in life would be a soft spot. Or that the 
>brain of Triceratops is actually just a little below the orbit's.

I'm not sure how this relates, but it is interesting.  Is this simply
a way to lighten the skull, or did something fill the space.

>Well, whale's swim with an up and down motion of he tail, Ichthyosaurs 
>swim with side to side. Ichthyosaur orbit's are large, nose small, 
>vertebrae are more like sharks in makeup than dolphins. Ichthyosaurs 
>are not like dolphin's and shouldn't even be drawn with them leaping 
>out of the water! (though it is a interesting drawing).

Except that one could claim that dolphins and Ichthyosaurs are BOTH
convergent with sharks (or any "high performance" fish).  All three
have evolved into the high-speed marine predator niche.  The only
difference is that for dolphins, the plane of thrust is 90 degrees
different from the shark, but I don't think that radically changes the
lifestyle.

>Yes, there is convergent evolution, but we must use the correct 
>convergent animals.

And I suggest that analogies are far more common, if we allow a little
flexibility.  Granted, things can be taken too far, but a claim made
with a resonable amount of evidence should be tolerated.

Rob Meyerson
Orphan Vertebrate Paleontologist

***
"I think I'll go stick my head in the station's nuclear reactor."
        -L.M.