Claws of Baryonyx and Sinosauropteryx

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Tom Pearce wrote:

>Though I've never observed them in the wild, there have been a number
>of superb documentary films that show grizzlies:

>a) Crashing through shallow ponds & rivers chasing fish, seizing them
>in their jaws...
>b) Waiting by the shores of a river & snatching them with their jaws,
>and most spectacularly...
>c) Standing at the top of a waterfall & snatching the salmon from the
>air as they leap up (in their jaws)!

>I've never seen them "hooking" fish from the water - then again, maybe
>I'm just watching the wrong TV shows!

Well, you're watching the same shows that I am (that's not to say that they
aren't necessarily the *right* shows).  ;-)  The thing is, I've never pinned
down a source (literary, televisual, eyewitness, whatever) that has
established that bears gaff fish from the water with their claws.

_Sinosauropteryx_ also has an enlarged claw on its hand (first digit),
usually interpreted as a specialized raptorial tool.  Rather than being a
specialized fish-catching intrument in _Baryonyx_, the enlarged claw of
spinosaurs may served a comparable function to the enlarged manus claw of
compsognathids.  Nobody (AFAIK) has ever suggested that _Compsognathus_ was
a specialized fish-eater - and the Solnhofen deposits are famous for their
fossil fish.

In broader functional anatomical terms, the possession of enlarged manus
claws in spinosaurs and compsognathids, and the enlarged pedal claws in
higher maniraptorans (?and noasaurids), may reflect separate strategies for
the seizure and dispatching of prey.  In some theropod lineages, the hands
were important in both functions; whereas in other lineages the pes took on
a greater role in killing prey and the manus became specialized for
grasping.  Other, larger theropods (like tyrannosaurids) used yet another
strategy for procuring and processing prey.



Tim