[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

> > OTOH, these arboreal characters are exaptations in
> most living gliders. Flying squirrels are perhaps most
> adapted, but *Draco* and colugos really just expanded on a
> pre-existing theme.
> I'm not sure what you mean here.

"These" -> "the above". The living parachuters/gliders that are compared with 
Archie are all derived from splay-legged animals anyway, with flying squirrels 
perhaps being the most derived as regards posture/limb/shoulder/pelvic anatomy.

So given that *Draco*, colugos and flying frogs are derived from ancestors with 
the correct anatomy for their mode of climbing, it is obvious that they would 
expand on it as they did, and as we *know* to be a good way towards a very 
arboreal lifestyle.

This *would not* be the way Archie would have struggled up a vertical early or 
pre-spermatophyte (-> non-branching) trunk say 5 ft high. Such a structure it 
definitely *could* have used as a lookout and "perch" (except it would really 
stand atop the fronds/leaves, not perch on branches). That much we can tell - 
it was neither adapted to sprawl-limbed climbing, nor would that be terribly 
efficient to get up . A running jump and a few lunges with the hand claws would 
to the trick better.

And a perch of that height was all it needed to give its flight capability a 
definite and massive edge. It could swoop dowen on prey and keep an eye out for 
predators. And there were no colugos and flying squirrels and tree kangaroos 
and birds and other competitors, while parachuting lizards and frogs would 
better *not* have shared a trunk with Archie for their own good.

There is really no analogue among modern birds, but seriemas might compare as 
regards the use of any higher-up site as lookout and launch site.

As soon as Archie was more than 3-4 ft above ground, it *would* have been 
technically able to fly for dozens, perhaps hundreds of meters in most cases. 
That we also can tell. A free-standing launch site also allows to make best use 
of the wind. In such a situation, Archie's flight ability would be most 
efficiently exploited. But did it encounter sufficient elevated spots and would 
it have found it easy enough to get up there?

Modern weak-flying landbirds - especially Galliformes - often use a kind of 
catapult launch, running to speed and only then pushing off and beating. 
Beating with all they got. One can see it when "flushing" a quail, pheasant, 
partridge etc; they accelerate with little or no wing involvement (it's 
pointless when you are not on open ground but in grass cover) and then burst up 
into the air. From raw power output, Archie could have done it maybe, but from 
its shoulder girdle - without a hypertrophied sternum and as it seems without a 
rotated scapula -, I am unsure. The real problem with the cursorial hypothesis 
is not take-off, but to get more than a foot (the actual animal's foot) or so 
off the ground, and *not* bounce into an invisible ceiling and go down again 
after 2-5 meters.

Perhaps it would be worthwhile to get more geologists and geographers 
interested in the topic and hear what they can find out about the habitat both 
at the micro and the macro scales. Because IIRC, no Archie fossil has actually 
been found in a terrestrial sediment, so its precise range is unknown except 
that it must have been not too far from the lagoon or the carcasses would have 
become more disarticulated.



Do You Yahoo!?
Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen