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



That for sure proves that *if* Archie had any sort of climbing
ability, it did
not climb the same way as e.g. a gliding squirrel or a _Draco_. But the
"theropods couldn't" argument still needs to explain how something like
_Microraptor_ evolved in the first place and by all accounts was quite
successful.<<<

It seems to me that puts the theoretical cart before the empirical horse. If theropods as a group (including Microraptor) lack evidence of specialization to engage in the bahaviors that have been hypothesized for Microraptor then it is up to us to come up with better (non-falsififed) hypotheses; it is _not_ the job of the morphology to conform to preconceived notions on how flight "should have" evolved (or when it evolved).

That's not to take a side on the issue of Microraptor volancy and arboreality right now (thought I have in the past), as there are some lines of inquiry I'd like to follow up when my schedule allows, so for the moment I have no official opinion on the matter.


Scott Hartman Science Director Wyoming Dinosaur Center 110 Carter Ranch Rd. Thermopolis, WY 82443 (800) 455-3466 ext. 230 Cell: (307) 921-8333

www.skeletaldrawing.com


-----Original Message-----
From: evelyn sobielski <koreke77@yahoo.de>
To: dinosaur@usc.edu
Sent: Wed, 10 Sep 2008 2:40 pm
Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)




That of course is probably a bet
ter question, but takes us
right back
to wrist and ankle morphology.  I am unaware of any
analogous trunk
climbers that lack highly mobile ankles and wrists (and
femora, for
that matter).  These guys all sprawl and twist their hands
and feet
around to get up the substrate, which Archaeopteryx (and
other
manirap...heck: theropods) could not do.

That for sure proves that *if* Archie had any sort of climbing ability, it did
not climb the same way as e.g. a gliding squirrel or a _Draco_. But the
"theropods couldn't" argument still needs to explain how something like
_Microraptor_ evolved in the first place and by all accounts was quite
successful.


The question is not "are they as well-adapted as a flying squirrel?" but rather
"are they better-adapted than their predators and competitors?" Certainly better
than the predators, simply for being smaller. The rest is probably harder to
assess than it might seem. For example, was the vertebrate column flexible
enough to allow for a sort of geometer caterpillar-like "inching" movement? As
ungainly as that would have been, there were neither colugos nor flying
squirrels nor any other competitor in Jurassic Europe, so "ungainly" might not
have been "ungainly enough to prevent it". (This is not a hypothesis, but just a
possibility that might be investigated by anyone who sees fit. However, a
tetanuran tail with feathers could provide bracing -=2
0in which case, with as much
certainty as such things can be said, the tail feathers would have been black
for the most part if not completely).


BTW "crampons" - it took me some time to find out, but what I meant was actually
tekagi. Like here http://shikurai.files.wordpress.com/2008/01/tekagi-5.jpg and
here http://www.aegisteam.cz/obrazky/galerie/id120_011.jpg. They don't wedge
into the substrate like crampons (not regularly at least) but are placed into
cracks etc. Something any claw will do, as long as it's not too long and
straight, or too curved. In that respect, it would be good to really shred the
ground-up-tree-down dichotomy and look at the situation in living birds:
woodpeckers, treecreepers, nuthatches etc vs terrestrial birds vs titmice,
Pink-legged Graveteiro, parrots and other "acrobatic perchers".


I'm not saying Archaeopteryx could never, ever get into
a tree.  If an
archie found a tree (no easy chore in its particular
environment) and
was highly motivated (perhaps a competition?) I'm sure
they could
manage to scamper up some form of tree.  I'm just
pointing out that
they lack specializations for the activity, and exhibit
several that
hinder climbing,

I'll just twist this round, not because I subscribe to either view (as of now)
but just for good measure:
"I'm not saying that Archie could never, ever take off from the ground. If it
would an elevated ar
ea (no easy chore on a subtropical lagoon island) and was
highly aided by circumstances (perhaps WAIRing its way up) I'm sure they could
achieve flight. I'm just pointing out that Archie's pectoral girdle is devoid of
anything that could have pushed its glide ratio high enough to achieve take-off
on a regular basis from level ground."


The problem is twofold: it was not adapted enough for climbing in any way we can
parallel in living organisms. And the ground-up scenario has always been
hampered by aerodynamics. Archie was a good parachutist, but with little more
ability to raise its arms than any terrestrial theropod, it would have found it
very very hard to leave the zone of ground effect. With its leg length and
wingspan, it is doubtful whether Archie would actually fly until out of ground
effect, if taking off ground-up: the lift generated by simply spreading its
wings and running would perhaps be enough to get the animal out of the ground
effect zone, but whether it would be enough to overcome the increased drag above
IONO.


WAIR might actually not help very much. Though their flight apparatus is very
different, even a two-week-old partridge is probably more capable of WAIR than
an adult Archie. It is not hard to see why WAIR research uses youngster
Galliformes; they are among living birds those who are a) of a weakly-flying
lineage, hence most in need of it and b) hyperprec
ocial and thus most capable of
it among birds of comparable age. WAIR does not occur in other living birds very
often or at all, and it is something that really shines when you have short and
round wings and a sophisticaterd and powerfully-muscled pectoral girdle, not the
other way around as in Archie.


For the moment, I prefer to remain equivocal, noting just that Archie's flight
adaptations might have been most effective when it found an elevated spot of any
sort, jumped, and gave a few of the half-wingstrokes it *certainly* was fully
capable of.



Regards,

Eike

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