Sail vs Hump?

[Dinogeorge@aol.com]

Rob Meyerson wrote:

> On a semi-similar point, he looked closely at _Oranosaurus_ (sp?)
> [_Ouranosaurus_: G.O.].  After adding the hump, he found that the
> pelvic region was located too far back to justify the idea of a
> bipedal animal (unless it was standing on a hill, with it's tail
> tilted downward:-).  He concluded that _Oranosaurus_ was fully
> quadrepedal.  Another interesting notion is that the pelvis of
> _Spinosaurus_ is located in a similar position to _Oranosaurus_.  If
> this is true, then _Spinosaurus_ would be the only quadrepedal
> theropod known.
>
> Comments?

One problem with restoring the sail of _Spinosaurus_ as a hump is that it is
so darned tall. Another is that the dorsal vertebrae are quite opisthocoelous
(i.e., the vertebral centra articulate with their neighbors in
ball-and-socket joints in which the socket is at the back of the centrum and
holds the ball at the front of the succeeding centrum). This indicates
mobility of the vertebral column and strongly suggests it was not
buried/immobilized in a great mass of flesh. Also, there is a natural "water
line" (for want of a better term) fairly low up the _Spinosaurus_ neural
spines, above which the lateral profiles and surface texture of the spines
change. This "water line" is likely where the back ended and the sail began.

I've seen a few quadrupedal restorations of _Spinosaurus_ in recent popular
dinosaur books. But until we know something of the forelimb, we cannot be
certain of its posture. I recall a large manual claw, something like that of
_Baryonyx_, found at Baharija Oasis, but I can't for the life of me dig up
the reference. If such a claw occurred in _Spinosaurus_, it would mitigate
against a quadrupedal stance (though not completely disprove it: the claw
could have been held off the ground like the pedal "killer claws" of
dromaeosaurids). Anyone else out there recall this baryonychid-like claw?