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Re: Screaming dromaeosaur biplane killers of the air



Apologies if I repeat what other people may have answered to this; I don't
get DML mails in a particular order, the "previous mail in this thread"
mentioned below arrived (exactly) 3 hours after this one:

----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Sent: Saturday, January 25, 2003 5:26 AM

> The actual wing feathers are, as
> shown in the type and in *Microraptor gui,* fairly short, with the longest
> wing feather shorter than the bony arm (I wrote on this before).

In the right wing of the holotype (Fig. 1 of the Nature paper), the longest
feather (3rd primary?) is very similar in length to the bony arm, isn't it?
(Probably it is a little shorter, but its base is prepared away to expose
the 3rd finger.)

> The aspect ratio is thus 5.77. This is similar to birds with soaring or
> speed-adapted wings, not what you would expect in such a primitive flier.

Depending on what a primitive flier is. Confuciusornithids have pretty long
wings, so that IIRC Rayner in the Ostrom Symposium volume concluded they
must have flown like swifts, at constant high speeds. Apparently unlike *M.
gui* they lack alulae.

> Rather, very short secondaries appear consistent with the other
> maniraptorans which have partial wings but do not seem to be able to fly
> (e.g., *Caudipteryx*).

Whose wings are much shorter.

>   There is also a problem with the use of a biplane analogy: biplanes have
> two foils, one above the other, rather than a foil behind the other, one
> which has a narrower, broader curved design than the wing itself. The butt
> fans [ :) ] also seem to have been much less than horizontal, given the
> lack of a lateral extension of the femur in *Microraptor* (see previous
> post in this thread).

_If_ the metatarsal remiges pointed laterally instead of (as preserved, in
2D specimens and with the feather bases ?preserved away) caudally, and if
*M.* flew in a squatting position, then it is imaginable that the metatarsal
remiges formed an airfoil below that that was formed by the arm feathers.
What that would have been good for is another question. In one respect it
would be less weird than Nature's reconstruction: the primaries of hands and
feet would be parallel, instead of those of the feet pointing backwards. On
the other hand, what if the foot feathers were mobile, able to be folded up
(for running) and down (for flying/gliding/...)...

> <In no way are the Johel sinornithosaurs (incl microraptors) mere gliders
> that retained the ancestoral dino-avian protoflight condition into the
> Cretaceous.>
>
>   One might want to be a bit more theoretical in this statement.

Above you write that *M. gui* had narrow arm wings, below you write that it
had no ability to sprawl -- should make gliding difficult, except perhaps in
the pose I imagine above, which would produce a bit much drag for a glider,
right?

> *Archaeopteryx* has a more avian tarsus and foot,
> with a reversed hallux and

A more avian tarsus? Why?
What about Middleton's doubts about the reverted hallux?

> This doesn't stop the mammologists who have the older marsupials
> in the fossil record before the oldest monotremes appear.

And indeed, mammalogists' predictions were right, the oldest
australosphenidans are a lot older than the oldest metatherians. (Crown
group marsupials are still unknown from the Mesozoic.)

> As for flight adaptations, *Archaeopteryx* was
> likely the better flier in having a longer arm,

while *M. gui* has arms that are only as long as those of...
confuciusornithids. Okay, the latter appear to have a bit longer hands, and
considerably longer remiges.

> broad primary fan,

In the holotype of *M. gui*, the right wrist is maximally flexed, therefore
the primary fan is maximally folded, and its appearance in a more extended
position hard to judge (from Fig. 1 and 2 of the Nature paper). The left
wing is incomplete.

> longer primaries than arms,

See above.

> a shorter trunk and shorter hindlegs

In comparison to what? The trunk-leg ratio looks very similar in *M. gui*
and *Archaeopteryx*.

> with a specialized, lighter skull,

Please elaborate. I only see a small snout there; the size of the antorbital
fenestra of *M. gui* appears to be unknown. (If it's large then the snout
can be as light as Archie's, I assume, while being as high as preserved.)

> a more advanced humeral elevator system and
> incipient triosseal canal with a taller and more proximal acrocoracoid,

Can you see this from the figures in the Nature paper? :-/

> less-fixed coracoid to scapulocoracoid,

Still sutured in Archie, as usual.

> and more prominent acromial process

Apparently.

> with rounded, U-shaped furcula, as in more advanced birds.

And oviraptorids, and *Bambiraptor*...

> Confuciusornithids are further advanced in the
> [...] brevity of the pelvis.

Not of the pubis, though.