Re: Archaeopteryx flight

[Dinogeorge@aol.com]

In a message dated 9/4/01 4:37:27 PM EST, z_heraklides@hotmail.com writes:

<< JEEZ JEEZ JEEZ. >>

Here I must agree with Zoe.

Incidentally, I'm not so sure that studying just the bones of the theropod 
manus will provide a definitive conclusion about how opposable the various 
digits were, how much they could flex, and so forth. (Although >not< studying 
the bones certainly won't shed light on the situation!). The attachments and 
sizes of the soft parts of the manus (ligaments, forearm muscles, e.g.) are 
critically important in determining the actual (as opposed to--sorry about 
this pun--the "theoretical," or bone-defined) excursion limits of the digits, 
as is the amount of cartilage in the carpus, the flexibility of the forearm, 
and so forth.

In the human palm, the first metacarpal is quite mobile relative to the other 
metacarpals, which is a major factor in the opposability of the thumb. In 
theropods, the short, thick first metacarpal does not seem so mobile, and 
most of the pollex opposability probably lay in the phalanges. In Syntarsus 
and Dilophosaurus the first metacarpal does seem to lie out of plane with the 
other metacarpals, and Galton (1971) argued that the pollex (of Syntarsus) 
was therefore opposable to the other digits. In Ceratosaurus, the first 
metacarpal was differently shaped, so any opposability might have been more 
constrained; I don't think we have a full set of manual phalanges for this 
genus. In tetanurans the first metacarpal lies pretty much in the same plane 
as the others and the digits radiate more or less uniformly from the carpus, 
although the first remains noticeably thicker and stronger. This suggests 
that the pollex was no longer opposable--or at least, not nearly as opposable 
as in ceratosaurs--although it had some kind of independent functionality 
within the hand.

Tough to study this stuff even if you have the specimens in hand (another 
%$#@ pun; sorry).