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Re: HUMPED OURANOSAURS (Spinosaurus actually)



Darren Naish writes:

>Not so fast Rob. The logic was not convincing and the neural spines of
>_Spinosaurus_ sure don't look like they supported a hump to me. Mammals (like
>bison) with tall neural spines just can't serve as models for tall-spined
>dinosaurs.

I disagree; as they say, form follows function.  If features found in
different animals are morphologically similar, then we can be pretty
certain that those features were used for the same purposes (the definition
of "convergent evolution").  Across the board, mammals with flat,
blade-shaped neural spines have some kind of hump structure, ranging from a
camel's fat-laiden hump, to a pig's muscle laiden hump (The only time we
see a sail is when the spines are thin and needle-like).  Since the spines
of _Spinosaurus_ have this same morphology, then some kind of hump
structure should have existed.  As your favorite sage would say, "Size
matters not."

>And the suggestion that _Spinosaurus_ had a hump because it was 'the
>camel of its day' is not realistic.  _Spinosaurus_ was not living in a xeric
>waterless desert and was not under camel-like selection pressures.

This was merely an possible explanation, I was unaware of the
paleoenvironment (and was guessing from the illustrations I've seen).

>Incidentally, has anyone really tried to reconstruct the Cenomanian north
>African environment? A fair amount of literature seems to suggest that the area
>was well-watered and densely vegetated - obviously those who think
>>_Spinosaurus_
>was a semi-aquatic predator (see Spinar and Currie 1994) presume it frequented
>wetlands of one sort or another. Meanwhile... was the environment these animals
>lived in deltaic or estuarine? Like I said before, in the _Edmarka rex_ paper,
>Bakker et al. reasoned that _Spinosaurus_ (and _Carcharodontosaurus_ and
>_Bahariasaurus_) was a marine analogue of 'early Tertiary seals and whales'!

Perhaps a better analogy (due to the estuary envronment) was that the
spines supported neck, front leg, and back leg muscles.  This would make a
much stronger animal; and could possibly support the semi-aquatic,
seal-like analogy.  If the seal idea is valid (I don't quite buy it), then
a hump would make the animal more streamlined, and more effective in the
water.

Unless of course, _Spinosaurus_ used the sail in the traditional sense (ya'
think it knew how to tack :^).

Rob Meyerson
Orphan Vertebrate Paleontologist

***
"The Universe is already mad, any addition would be redundant."
        -L.M.