Re: Archaeopteryx flight

["David Marjanovic" <david.marjanovic@gmx.at>]

> 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.

Surely *Archaeopteryx* was more generalized (it was obviously a better
runner than any contemporary pterosaur*); however, looking at recent
ecosystems, there are always plenty of potentially competing fish eaters.
I've seen dolphins on TV hunting a large swarm of IIRC anchovis just below
the surface -- gulls took advantage of this and picked some fish up from
above, and a few seals joined in too; the swarm was so large that it cannot
have visibly diminished in size. Another example are the Galápagos islands
where there are flightless cormorants and penguins among lots of flying
piscivorous birds. So it seems like there normally are enough fish to share
around.

* Paul also shows that it was a considerably worse runner than most other
theropods -- the ilium and various muscle attachment sites (cnemial crest
etc.) are very small.

> >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.

Exaptation :-)

> However, continued
> use of the manus in any sort of predatory or scavenging activity risked
> fouling the wing feathers [...].  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.

I disagree: the fingers flexed, and the claws pointed, more or less at a
right angle to the wing feathers. The exceptional development of finger III
in *Confuciusornis* shows that it was still used for something.

> >[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.)

I agree with all this :-) -- additionally the pedal claws look less like
those of fish-eating bats than the manual ones.

> >*** 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.

Indeed he thinks (or thought in 1988) that *Archaeopteryx* had a similar
locomotory repertoire to young hoatzins. I think that climbing is largely
ruled out, however. Flying may have been impossible according to the old
feather-asymmetry paper the citation of which I just cited :-) .
"surely much less bound to swimming than Archie"? :-)

BTW, does the scapulocoracoid joint occur in *Protopteryx*, *Longipteryx*
and/or *Jibeinia*?

While I am at it, I've just received The Scientific American Book of
Dinosaurs and Mesozoic Vertebrate Life. The latter includes a drawing of a
tail feather of *Protarchaeopteryx* -- it is slightly asymmetric :-o -- and
of the tail end of *Caudipteryx* -- the last caudal is IMHO a bit long and
oddly pointed, I still can't say whether it is half a *Nomingia*-style
pygostyle...