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Rob Meyerson said..
> As an aside, there was an idea presented at the last North-Central GSA
> meeting, which may close the door on the idea of a "sail-backed" theropod
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. 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.
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'!
Might they have used marine sediments local to the _Spinosaurus_ locality in
making this, err, radical decision? Finally, I recall a mention that the
_Spinosaurus_ locality in north Africa was thickly forested with brachyphylls -
aberrant gymnosperms that formed dense, mangrove environments.
(Oh, and incidentally, it's not really correct to refer to 'early Tertiary
seals' as the earliest seals are from the latest Oligocene/earliest Miocene.
Palaeocene-Eocene is 'early Tertiary' IMHO.)
A restoration of a scene set in the Cenomanian of north Africa, in the Long and
Welles' Bellerophon book _The Last Dinosaurs_, in fact has _Spinosaurus_ and (I
think) a dicraeosaur in amongst dense brachyphyll mangrove stands. I can't
realistically see tall neural spines evolving, however, as foliage deflectors.
Cassowaries, with dense resistant plumage, and forest rhinos, with thick
calloused skin, appear to have adaptations that would assist in moving through
dense bush. _But_, it's very hard to see how having a row of super-tall webbed
spines along your back would be helpful in such a situation.
Tim Williams said (with re to notions of a fat/muscle hump over the spines)..
> For _Ouranosaurus_, sure. (I'd love to see the illos of this!).
William Stout has done a restoration of a humped _Ouranosaurus_, but I forget
where I saw it. Maybe in Donald Glut's _Dinosaur Dictionary_.
"I've been playing table tennis (pause) with mice"
"Are they.. dead?"