Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

["Jaime A. Headden" <qilongia@yahoo.com>]

Augusto Haro wrote:

<This indicates that *Microraptor* is far removed from the base of the 
Deinonychosauria.>

This is not as relevant as it may seem. If your case was to use 
*Archaeopteryx*, *Microraptor*, then a given largem-bodied dromaeosaur like 
*Velociraptor*, and a few birds, we can get this:

--+--+--Microraptor
  |  `--Velociraptor
  `--+--Archaeopteryx
     `--+--Jeholornis
        `--+--Sapeornis
           `--+--Confuciusornis
              `--More stuff

  If we were to take this tree and compare the physical morphologies of the 
nodes to one another to figure out which came first, and which was derived from 
that condition, I would asusme we would at first infer that it was 
*Microraptor* first, as it derived from the ancestor of *Microraptor* and 
*Archaeopteryx* "first", or at least its lineage did. However, its morphology 
of feather anatomy is, so far, limited to itself. this thus gives us a hefty 
constraint that we cannot infer that morphology to the given posited ancestor, 
just to a descendant, for which we have evidence of. *Archaeopteryx* lacks this 
characteristic morphology, and in  fact possesses far different pectoral, 
pelvic, and limb morphology in having longer arms, shorter legs, relatively 
shorter-proportioned legs and larger arms to body size, and so forth. We can 
not only posit that they two animals have derived substantively from a similar 
ancestor, but they have done so in different
 directions. To argue that one of them is representative of the native 
condition without knowing what morphology came first is not informative and in 
fact rather phenetic. If we argue that *Mahakala* came first, was at the root 
of this tree for the sake of Paraves, we must derive from its morphology the 
conditions of both *Archaeopteryx* and *Microraptor*. Neither of the end 
products changes position simply because it might have more phenetic similarity 
to the other, if both (again) derived from the same conditional ancestor, even 
if it was something like *Mahakala*.

  (I also advise you to read up on several of the other phylogenies, as well as 
Senter's work on the topic. Note also that Turner et al. is a variation of the 
Theropod Working Group matrix, which is essentially the same phylogeny growing 
over the last 10 years.)

<With respect to the possibility of femoral abduction in *Microraptor* itself, 
I agree that the preserved position is an artifact, and think not so much 
abduction was possible, but that does not mean the angle of adduction in birds 
is impossible.>

  I did not argue that avian abduction was impossible, but that microraptorian 
eversion was. 

<Jaime, do you refer to the *trochanter femoris* when you say trochanteric 
body?>

  I refer to the region of the proximal femur whereupon the trochanters arise 
lateral to the femoral neck and caput (I'm not using the Latin, simply because 
avian morphology is so much more modified than the condition in *Microraptor* 
in this case). here you not only have the proximal greater trochanter, which 
apparently abuts the acetabular dorsal shelf and posteriorly contacts the 
antitrochanter, but also the anterior trochanter above the lesser which are 
rather low compared to the condition in, say, *Velociraptor* (i.e., the femoral 
caput is relatively elevated, although this may be an artifact in Hwang et al.s 
studied specimens, since the material is a bit crushed and distorted, and may 
also indicate splay of the elements). In birds, a different morphology permits 
movement of the femur not possible (lateral eversion of the shaft about the 
long axis and outward from the body midline) in *Microraptor*, based at least 
on Hwang et al. This says nothing
 about birds.

<I fail to see differences between *Microraptor* and birds that can prevent the 
femur of *Microraptor* to achieve many of the movements seen in birds. Applying 
the Extant Phylogenetic Bracket approach (Witmer, 1995), we should infer, if 
there is no compelling anatomical evidence against, that abduction was possible 
at full retraction not only in *Microraptor*, but in other dinosaurs as well, 
as it is present in their closest living relatives, Crocodylia and Neornithes.>

  Except that this is not possible in most dinosaurs. Unlike crocodilians, the 
basal condition for dinosaurs and therefore theropods and birds, is a bipedal 
arrangement with a fully perforate acetabulum, cylindrical caput with virtually 
NO neck, and a broad and high greater trochanter and antitrochanteric contact, 
that not only restricts posterior but also lateral excursion of the femur, 
medial excursion, and essentially restricts the femur to a 
forward-then-back-to-neutral mobility. Only in smaller animals does this become 
less constrained, so in this sense, the bracket says nothing simply because 
morphology contradicts it (morphology trumps assumptions of what it should be 
if we know of it -- Witmer's EPB arguments apply to what is NOT known of the 
representative taxa between known extents).

  Cheers,

Jaime A. Headden

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