Re: Archaeopteryx flight

["Tim Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic wrote (quoting Greg Paul's PDW):

> We have already seen how the conical teeth of some small
> theropods were suitable for fishing. In fact, the very conical, unserrated,
> and big-rooted teeth of *Archaeopteryx* are most like those of marine
> crocodilians, whales, and the toothed diving bird *Hesperornis*.

This would put _Archaeopteryx_ in direct competition with the 
rhamphorhynchids.  The latter had jaws and teeth specialized for piscivory, 
including procumbent teeth at the front of the jaws.  The rhamphorhynchids 
may also have been superior fliers.

Perhaps there was enough fish to share around.  But I like the idea that 
_Archaepteryx_ was a more generalized and opportunistic carnivore, with 
fish, insects, small vertebrates, and carrion all comprising a part of its 
diet.

> Not only
> that, but the hooked and laterally flattened claws, especially those of the
> hands, are strikingly like the toe claws of fish-eating bats (Figure 9-4)

I know the morphology of _Archaeopteryx_'s manus has diverged very little 
from that of ground-dwelling predatory maniraptorans.  However, continued 
use of the manus in any sort of predatory or scavenging activity risked 
fouling the wing feathers which, even at this early stage of avian 
evolution, were no doubt integral to the ecology of _Archaeopteryx_.  I 
think by the stage of avian evolution exemplified by _Archaeopteryx_, the 
forelimb and manus may have been largely decoupled from the theropod's 
trophic or predatory behavior.

> [which shows that the claw curvatures are very similar indeed, a bit more 
> so
> with Archie's hand claws than with its foot claws].

As with the enhanced perching abilities ascribed to _Archaeopteryx_'s pes by 
Feduccia, claw curvature gets you only half the way: the pedal claws have to 
be able to meet in order to grasp effectively.  The pedal digits of 
_Archaeopteryx_ show little opposability - though the reversed and more 
distal hallux (also described for _Microraptor_) shows a trend in this 
direction.  This, and the rather weakly developed flexor tubercles of the 
pedal digits, makes the foot of _Archaeopteryx_ a rather poor prehensile 
device - and therefore poorly adapted either for perching or seizing prey.  
(I am aware that certain people, including one or two on this list, might 
disagree with the latter interpretation, and that there is work in progress 
on this very topic.)

> *** Any evidence of water near *Rahonavis*? That said, it has a joint
> between the scapula and the coracoid, so it was a much better flier and
> surely not bound to swimming.

David, I don't think Greg Paul is claiming that _Archaeopteryx_ was "bound 
to swimming", only that swimming formed *part* of its behavioral repertoire. 
 Just like the hoatzin, which is capable of a lot of weird stuff, as both 
juveniles and adults.


Tim




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