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Re: Screaming dromaeosaur biplane killers of the air



I wrote (in double corner brackets ?<< >>?):

<<[S]imilar to the positive evidence that *Caudipteryx* lacked tertials of
any note as the secondaries reduce distally towards the bone.>>

David Marjanovic (david.marjanovic@gmx.at) wrote (in single corner
brackets ?< >?):

<Part of this may be an artifact of the slabs splitting between the
gastroliths, leaving the inner wing feathers buried in the upper slab.>

  Indeed, this works both ways. 

<<The characters, as are noted for *Sinornithosaurus* (pg. 239, for
instance), show that it, despite lacking a wing, "despite all of its
well-developed flight features.">>

<What do you mean? "[S]how that it" what?>

  I left out the concluding clause: ??"despite all of its well-developed
flight features," *Sinornithosaurus* could fly. However, it can?t. It
would thus be considerable if the same features occur in other winged
theropods that these features are not in fact indicative of flight.?

<<I do in fact refer to the M. supracoracoideus which, as restored for
*Archaeopteryx* (in PDW) is advanced above that of *Sinornithosaurus* with
a larger, taller acromion, with the incipient triosseal canal. This is
less derived in *Sinornithosaurus* and *Microraptor*.>

<But doesn't mean they were unable to flap. This character may well have
phylogenetic significance, however.>

  I did point this out later in the post. As also pointed out, flapping
occurs via a large amount of muscles. Nevertheless, the ?advanced avian
system? Paul referred to involves the relative positions of muscles
relative to the humerus and around the glenoid. In birds, the deltoideus,
coracobrachialis and supracoracoideus attach ventrally to the glenoid, and
surround the head of the humerus; in non-avian theropods with a cranial,
non-reflexed coracoid, the muscles attach _in front_ of the humerus, and
anchor instead on the humerus at only three sides, rather than all around
it. This is an essential shoulder design relative to the motion capable in
it, that is both phylogenetic and biomechanically constraining on methods
of wing control.

<<I should have clarified this; the reduced lateral curvature in basal
birds reflects in increase in medial curvature and a lateralization of the
glenoid and broadening of the shoulder,>>

<The glenoid is already lateral, isn't it? When did it shift dorsally, at
the root of Ornithothoraces?>

  In dromaeosaurs, Paul and Xu et al. indicate that the form of the
scapula shows a lateral glenoid. But this is less so in other
dromaeosaurs, where it faces more ventrally than in *Microraptor*.

<<[W]hich works toward a more advanced pectoral arrangement as in modern
birds, providing a sort of rotating or "spring" system in the sternum and
coracoid, medial compression of the shoulder during the downstroke.>>

<But certainly not as in Confuciusornithidae, whose furculae didn't allow
this, unless I miss something obvious.>

  Confuciusornithids also lack the ?advanced? coracoid design and
orientation, as well as a developed triosseal canal, though the
acrocoracoid process is developed slightly above the level of the glenoid.
The furcula of confuciusornithids as well as *Archaeopteryx* are
non-compressive, but this is advanced relative to the morphology of the
?earlier? dromaeosaurs (*Microraptor*, *Sinornithosaurus*, *Velociraptor*,
and NGMC 91 have slender, S-shaped rami with an apical furcular
symphyses). They are different from that of enantiornithines, *Boluchia*,
and basal ornithothoracines, where the furculae are Y-shaped, have broad
rami that are more C-shaped in section than L-shaped as in *Archaeopteryx*
and *Microraptor*, or than subcircular (slightly flattened) as in
*Velociraptor*. One cannot argue that these, or even the furculae of more
?basal? dromaeosaurs, indicate a more advanced avian system.

<<However, because [?] screamers lack fused uncinates is irrelevant, the
remainder of birds show them present, and their absence in screamers is
likely autapomorphic for a group of birds (anseriforms) that possess them
nearly universally, as 
well as most ratites, tinamous, and nearly all other ornithothoracine
birds.>>

<To me it looks like uncinates ossify whenever they choose to. In the
university's geocenter there's a moa skeleton exhibited, the first right
dorsal rib is missing, the first left dorsal rib has a small semicircular
uncinate process, and the other ribs don't have anything of that sort. No
currently unquestioned member of Enantiornithes is known to have
uncinates. *Protopteryx* and *Longipteryx* have them, I forgot about
*Jibeinia*, confuciusornithids have them, *Sapeornis* appears to lack
them, and a few specimens of oviraptorids and dromaeosaurids have them.
And then comes Willo with its huge uncinate plates that remind one of
*Eryops* or *Ichthyostega*... ~:-|>

  I believe the condition in early tetrapods and cynodonts, as in
ornithomimosaurs, have been shown to be outgrowths from the caudal margin
of the rib. In ?Willo?, some plates appear to be fully integrated into the
rib, and suggest both that the posterior ?loose? plates are unfused
structures, or are broken outgrowths. The specimen has not been published,
and this region not studied to the point that it can be verified, so it
inconclusive. Only birds and tuataras show actual separate ossification
centers for the uncinates ribs that can be traced ontogenetically. Most
ratites have uncinates to the point that they are universally assumed to
be present to the point that specimens may not ossify. Skeletons of
cassowaries, rheas, and ostriches, as well as *Dinornis* among moa, kiwis
among their living sister group, have well-developed uncinates, thought
they are not known in large phorusrhacoids or aepyornithid ratites, or the
?super? ducks, *Gastornis* and *Bullockornis*.

<<Asymmetry of the feathers when the leg was extended would require
unusual and frankly impossible positions of the metatarsus (when the leg
was extended as in Xu et al., the feathers would point inward, not
outward, as the feathers _trail_ 
the metatarsus?>>

>That's exactly how they reconstruct it in Fig. 1: 2nd toes on the bottom,
4th toes on top, metatarsal feathers pointing caudally.>

  Xu et al. oriented the pes facing posteriorly volarly (sole), the
aerodynamic leading edge of the feathers facing laterally, not cranially,
and therefore not affecting a true airfoil when camber (if present) would
be transverse to the air stream.

<<[A]s the asymmetry favor the narrow vane towards the foot -->>

<Whatever that exactly means, if the preserved positions are real, then
the narrow vanes are distal to the rhaches*, again as reconstructed.>

Distal to the rachis? This would include both vanes. My phrase was to show
that, in a diagram:

 ______________________________  ? leading edge
/________________________________  ? rachis
\
 \______________________________ ? trailing edge

  that ?asymmetry favor the narrow vane towards the foot? would show that
the narrow vane faced towards the digits of the pes, or the ?foot.?

<<[I]f the condition of feather position is taphonomic and the feathers
were lateral to the metatarsus, the feathers would be oriented
_vertically_;>>

<Again when the legs were maximally sprawled, right?>

  Yes. It was included in the same sentence before I suggested
reorientation of the limb to another position as advocated on the list.

<<[W]hen the leg was tucked, as in birds, the metatarsus is horizontal,
the feathers face laterally, and the narrow vane was cranial, not caudal.
In the last, only then does the leg conform to the aerodynamic feathers.
This also explains the bowed and long fifth metatarsal, which may have
more likely bowed laterally as part of the feather support structure, and
not caudally as recently reconstructed.>>

<I think that this is the most likely flight position for *Microraptor
gui* (no opinion on synonymy), assuming that the feathers did face
laterally and not caudally from a vertical leg; I'll try to illustrate
this, as soon as the Web Publishing Wizard works and I get some time to
draw, and if you don't finish yours first, I assume yours will suffice to
illustrate what I think.>

  Go ahead. I will still offer a diagram of my concepts.

<I thought you were talking of the femoral head all the time, and
inadvertently wrote humerus (3 times or so) instead of femur, but if you
say that's not the case, then why is there suddenly a humerus in there?>

? and:

<Same.>

  Because that got by my spell checking and proofing.

<As also described above, the leg-wings and "buttfans" serve aerodynamic
function when the leg is tucked, not extended.>

  My structures imply the position of the feathers is fixed as in the
feathers as evidence for mobile feathers is lacking without creating now
structures involved. Paul suggests the metatarsals had dermal muscles to
control the feathers, as in the heads, breasts, and backs of birds. In the
arms, and tail, feather position is controlled by enveloping in the
tendons and muscles that are exapted in arm extension, folding, and
osseous tail movement, such as the humeral retractors, caudofemoralis
longus muscle around the retricial calami, and so forth. The alula is
controlled by the muscles in the alular digit, and these were all present
in the arm and tail prior to feather origin. In the metatarsus, similar
muscles do not exist, but tendons do, such as the various Tetanus flexor
digiti. These muscles ran along the ventral metatarsus, and if the
feathers were imbedded in them, they would flare outwards towards the
digits of the pes when ?fanned.?

<<And yes, the outer retrices of the peacock are more asymmetrical than
the inner.>>

<The inner ones are completely symmetrical. Don't know about the outer
ones.>

  As in all retrex-bearing birds, the innermost retrices are symmetrical
or nearly so. I also proclaimed lyrebirds, in which these feathers show
remarkable asymmetry.

<<4) for climbing>>

<Same as the predatory stroke, no?>

  In a different plane, perhaps so. The arm flexes at the elbow while the
humerus is retracted caudally, but the wrist is usually straightened
relative to the forearm, and it might better be explained is supination
were possible, whereas in the predatory stroke, it enhances the wrist
flexion, and supination is restricted.

<Maybe only because no cladistic analysis has yet integrated all those
"neoflightless characters" into its data matrix. Many of the characters
are IMHO worth such a try. Mickey M? :-)>

  Paul?s neoflightless characters are merely a revision of existing and
already integrated characters, where the primitive state versus the
advanced state is assumed in reverse to that shown in other phylogenies;
other phylogenies show a reverse condition in character/state codings
where the polarity is ordered, or assumed sequentially to each other.
Treating all the characters Paul considers indicative of a reversal
condition relative to birds merely requires the states be treated as
unordered. This can be done in the matrices of Hwang et al. (2002) and
Clarke et al. (2000, 2002) given the group one wants to focus on
(maniraptoriforms with only basal birds, or basal birds with the basal
radiation of carinatan birds, respectively).

<<[P]ro-urvögeln.>>

<The n is too much. Vögeln is a verb... a rare verb that, without a
logical etymology, describes vertical gene transfer. :-] Sorry: The n is
correct in the dative ("to the birds").>

  My knowledge was that ?n was a plural modifier. Is this Vögels?

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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