paleonet Old Four-wings

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"Feather-footed through the plashy Cretaceous, wanders the questing
Microraptor..."

First, here are my answers to the leg-winged dino-bird questions:

Why did they need tail wings?

Because they carried around a broomstick of a tail that at approaching 2.5
times as long as the trunk was extremely long, much longer than in
Archaeopteryx (1.6).

This will have caused a tail-down tendency during flight (even if you only
accept unpowered flight) not only because of the weight moment of the tail
but because it was largely unfeathered.  I delayed my acceptance of Czerkas'
reconstructions of flying dromaeosaurs having only a tuft at the end of the
tail but now it seems he was right.  Unlike in Archaeopteryx which had
feathers all the way down which presumably contributed significant albeit
inefficient lift, Microraptor gui et al. gained practically no lift from the
tail (the reconstruction on p336 of last week's Nature overstates the extent
of the tail tuft.)

This pitching-down tendency could be counteracted by providing significant
downlift somewhere near the front of the animal but that would be
inefficient; providing some of what lift is generated further aft would
address the problem more nicely if such a trick could be managed.  In short,
M. gui had leg wings because of the long unsupported tail.  The balance
imperative only applied to lift though, not thrust.  Aerodynamic thrust from
the legs need not come into it.

Why then the tail?  The tail was not a balancing pole, though it could be
used as one.  It was an energy storage device, just as one of the fighting
robots in "Robot Wars" uses a rotating disc to store destructive energy,
conducted to its victim by means of a projecting claw.  Well, not *just* as
in the robot since the tail didn't (I presume) move in repeated circles, but
simply in a downward arc.  Although a simple stamp can apply more force than
the weight to the ground or a victim for a short time, another relatively
inflexible organ flicked downwards and relatively quickly stopped can
accentuate such an ultra-weight force.  Not all long-tailed dino-birds had
specialised toe-2's, but all with such a toe had long thin tails.

The long tail led to the leg wings, and their loss in the descendants of
dromaeosaurs was due to the loss of the tail.  (Incidentally, there would be
no insurmountable aerodynamic problem in such tandem wings since primaries
of many normal birds' wings are essentially tandem, though they may be
staggered vertically; also some insects, some about as large as M. gui, had
powered tandem wings.  Modern dragonflies flap theirs 90 degrees out of
phase, quite happily.)

It was not until the hands could be used to snag and pull effectively that
such highly specialised toe weapons could be useful.  Classic Jurassic
theropods didn't have the arm geometry to make this feasible.  It was also
not until the tail had adopted an ability to be flicked up and down quickly
through a large angle that there was any sagital momentum storage facility
in the first place available for further enhancement.  The long arms and the
stiff flicky tail evolved for air-planing and were exapted for toe-slashing.
So e.g. Archaeopteryx first, then better fliers, such as flying dromaeosaurs
like M.gui later.

[For those not up-to-date with things, troodonts - the ancestors of all
arctometatarsalians - sprung off from primitive powered-flying stock near
Archaeopteryx, before the arrival of proper early dromaeosaurs with their
uncinate processes; oviraptors came from such early droms and were on the
line to modern birds.  All other lines of flying birds, those which didn't
have uncinate processes, such as, yes, confuciusornithids and all true
enants, radiated prior to the first dromaeosaurs.]


I don't know which are more fascinating: the bizarre antics of dino-bird
evolution, or of dino-bird evolutionists!

As usual, we see conventionalists, e.g. in this case Prum and Gee,
forgetting how pointless it is, indeed dangerous if successful
theoretisation is important, to consider only positive evidence, and for
your own theory at that.  They also show how good they are at getting other
people's theories wrong, and indeed at persistently ignoring theories that
might just be better than theirs.  Congratulations on digging out old Beebe
from the archives!  Next year will be the 20th anniversary of Greg Paul's
theory of secondarily flightless dromaeosaurs, and Gee still hasn't heard of
it.  It's even fifteen years since "Predatory Dinosaurs of the World".

Prum first:
He says a "well-corroborated" answer to the question of the origin of birds
is that they are a lineage of dinosaurs.  It is however even better
corroborated that the reverse is true.

He also states new fossils [etc.] "...have also supported a coherent
solution to [the question of the origin of feathers].  Feathers evolved in
theropod dinosaurs before the origin of birds or flight through a series of
developmental novelties."  Apart from their theory having no explanatory
power as regards these developmental novelties, the fossils support the
contradictory theory even better.

(He then takes time to acknowledge a paper which, in strong competition, was
probably the most scientifically incompetent I've ever read in Nature -
Burgers and Chiappe '99 399; 60-62: "Moreover, aerodynamic models of the
flight stroke of Archaeopteryx,[...], indicate that its wings could have
provided thrust as well as lift, and aided the legs in achieving enough
ground speed for a running take-off."  That paper never came anywhere near
even "indicating" that wing thrust would have allowed any extra running
speed, certainly not take-off speed (which they were guessing at anyway),
true though this might well have been.  It is certain that Archaeopteryx'
wings could have provided thrust, but we didn't need the paper to tell us
that.  The paper's diagrams also suggested the reaction from the ground
while the animal was at rest didn't go through the centre of gravity, and
that its thrust increased with speed.  It also set new standards for
linguistic style that anyone whose own paper has been rejected on such
grounds might find of interest.)

After introducing the trees-down vs. ground-up controversy, he then wheels
in Beebe's 1915 paper that suggested early fliers might have had four wings,
and considers in detail a trees-down theory where M. gui might instantiate
this 4-winger.  However, he completely ignores the fact that the main
trees-down theorists do not have dromaeosaurs as the first fliers.  Don't
bother about considering other people's theories, Richard!  Ignore the
literature (except Beebe 1915) and invent a new example to represent all us
tree-downers!  Xu et al. made many of the same mistakes admittedly but a
commentary doesn't have to be a precis.

He still had space to demonstrate his touching implicit faith in the
certainty of cladograms:  "...firm conclusions about the evolution of bird
flight will require new systemmatic analyses incorporating this and other
newly discovered theropod species[...] to confirm their phylogenetic
position."  Oh good.  "firm conclusions" ... "confirm their phylogenetic
position."  Since so many cladograms contradict each other, it is 100%
certain that most are wrong.  Why do you believe a 100% trustworthy one will
ever appear?  How will you know it when it does?  Angel Gabriel will tell
you I suppose.
Oh - in the penultimate paragraph he mentions me:  "Skeptics [ :-) ] will
argue in any case that Microraptor and dromaeosaurs are more closely related
to modern birds than is Archaeopteryx - but then they will also have to
address the problems of why a bird that could flap its wings perfectly well
would evolve a second pair of wings."  No problem pal - see above.  Next
time reference http://www.geocities.com/strangetruther/jj2ftree.html please.

Finally, his cladogram violates not just time but egg data too, with a nasty
reversal or two between ovis and troodonts.

Back to Gee again.  On the Nature website at
http://www.nature.com/nsu/030120/030120-7.html  &
http://www.nature.com/nsu/030120/030120-8.html  he says that to solve the
impasse between trees-down and ground-up... "one would need to find a
feathered dromaeosaur adapted to life in the trees rather than on the
ground."  Unless of course the main protagonists of trees-down didn't have
flight starting in droms.  But then who cares about Paul and me when there's
Beebe to quote.  The "need" he mentions is unscientific rubbish.

"Microraptor gui shows that true, birdlike feathers were a feature of
primitive dromaeosaurs long before birds appear in the fossil record..."  He
has clearly taken leave of his senses.  He's even got the cheek to say
"*long* before"!

(His claim that oviraptors [...are...] rather remote from the direct lineage
of birds is another wonderful hostage to fortune.)

However I do find the the following interesting:
"most palaeontologists now agree that birds share a common ancestry with
dinosaurs, in particular with small carnivores called dromaeosaurs."  That's
not quite how he usually puts it!  Might he and Feduccia be converging?