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Re: Spinosaurus redescribed as giant semiaquatic theropod

Dale McInnes wrote:

> I'm going to suggest something here. The way that spino's "fin" is now
> reconstructed is actually quite interesting. I'll leave it up to the authors 
> to
> defend that reconstruction. A "2-pointer" level fin [can't quite find the 
> right
> word for it] might be a lot more natural than a smoothly constructed
> semicircular fin, especially for camouflage. I would suppose that there would
> be a lot of debris in the form of branched logs floating around in thos
> backwaters where spino converged upon. A color pattern of a low horizontal
> thick brown/gray stripe accompanied with "branching" vertical stripes just
> might conceal this enormous predator in the form of a large floating branched
> log in amongst others. It just might get close enough to shore to grab an 
> unwary
> verte taking a drink. More stealth than a crocodile .. maybe.

The authors interpret _Spinosaurus_ as a semiaquatic predator that
targeted aquatic prey: sharks, sawfish, coelacanths, lungfish,
ray-finned fishes.  (BTW, there were some whopping big lungfish around
at the time.)  The concept of _Spinosaurus_ as an ambush predator
awaiting the approach of thirsty terrestrial prey is difficult to
accord with its overall size (specifically height).  It would be
difficult for an adult _Spinosaurus_ to 'lurk' in shallow water.

The piscivorous , semiaquatic lifestyle inferred for _Spinosaurus_ has
been compared to early cetaceans ("archaeocetes").  One major
difference is that early cetaceans evolved from terrestrial
quadrupeds, whereas theropods were bipeds (and still are).  The
semiaquatic _Spinosaurus_ has been regarded as a quadruped when on
land, due to its highly reduced pelvis and hindlimb.  We'll have to
see how this mooted terrestrial quadrupedality stacks up with future
discoveries regarding the pectoral/forelimb/manus morphology of
_Spinosaurus_.  It is even possible that _Spinosaurus_ rarely ventured
onto terra firma, except to lay eggs (like hesperornithids).

As a sidebar, the humerus referred to _Spinosaurus_ is especially contentious...