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Re: Screaming dromaeosaur biplane killers of the air



----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Sent: Friday, January 31, 2003 5:02 AM

The text of this e-mail was duplicated, resulting in a 57 KB post.

> similar to the positive evidence that *Caudipteryx* lacked tertials
> of any note as the secondaries reduce distally towards the bone.

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

> 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? "show that it" what?

> <[humeral elevators] you mean fully developed avian system, absent in bats
> and confuciusornid [sic!] grade birds>
>
>   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.

> <[reduced lateral coracoid edge] so?>
>
>   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?

> which 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.

> 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*... ~:-|

> _modus volati_.

volandi = of flying, genetive. Like modus vivendi = of living.

> 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.

> as 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.

* Or what is the original plural of rhachis? Rhacheis, like poleis? ~:-)

> if 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?

> when 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.

> <Note: Oops. I forgot that the Microraptor type is also preserved with the
>  legs splayed out, and without evidence for disarticulation although
> damage makes the situation non-definitive. More evidence for sprawling!>

Without evidence _for articulation_ I won't consider the preserved position
of a 2D fossil evidence for or against sprawling. A sprawling dinosaur is an
extraordinary claim that requires extraordinary evidence -- which a good
photo can obviously be, but the mere fact that the specimen sprawls cannot.
Birds that are preserved that way are common.

> <Contrary to these data, it seems the data I presented was overlooked a
> tad. NGMC 91 lacks known humeral proximal ends {what does this have to do
> with LEG function?],>
>
>   Paul was the one who is trying to make femora angle laterally ... as for
> leg function, I never said anything about leg function.

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?

> <has nothing to do with the discussion of the Jehol dromaeosaurs>
>
>   It shows, as I described, what a spherical, elevated humeral condyle
> would look like, as implied in *Sinornithosaurus*, and a demonstration
> that lateral leg splay

Same.

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

Depends on the position of the feathers on the metatarsus.

> 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.

> <Since there is no evidence for the ability to flap the legs the leg
> feathers were purely for generating lift for pertinent purposes, they did
> not generate thrust.>
>
>   Kicking motion with pes held vertically during horizontal glide path? I
> think this was suggested before.

Can't imagine this.

>   4) for climbing (I think Tim Williams is the most vocal proponent of
> this, and I am unaware apart from Chatterjee (1998) of anywhere it has
> been published in similar manner) where the sheer act of climbing causes
> the arm and shoulder adaptations assumed to be "flying" in nature,
> including the medial action of the arm, folding during lifting the body

Same as the predatory stroke, no?

> the fossil record [...] appears to support an
> alternate phylogeny that Paul fails to disprove.

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? :-)

> pro-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").