Re: New alvarezsaurid

["Jaime Headden" <jaemei@hotmail.com>]

<All ornithirines had a prokinetic snout as shown by Witmer and Martin. 
The new enantiornithine described by Sanz et al. had a very 
ornithurine-like quadrate with a prominent orbital process; the jugal is 
also reduced to a jugal bar in that enantiornithine. Cathayornis seems 
to have all of the features of the new enantiornithine with another 
feature: an ossified mesethmoid, which marks the development of a 
bird-like nasofrontal hinge in enantiornithines.>

Both Enantiornithes and Ornithurae are dead-end lines that did not 
develop all the characters relavant to Neornithes, including loss of 
true teeth, the keel, and pygostyle. Enantiornithines, of which 
constituency seem closer to Archie than other bird groups (*Sinornis*, 
*Patagopteryx*, *Eoalulavis*, *Protarchaeopteryx*, etc.) simply are to 
un--bird-like in the structure of their limbs, pelvises, and skulls.

<Archaeopteryx lost the ascending process of the jugal and 
squmosal-quadratojugal contact and had a relatively more adavanced 
quadrate, all of which suggest a primitive system of kinesis.>

This is seen in oviraptorosaurs, with a few added surprises, including a 
palate set below the maxillary rim, form of the pterygoid, and several 
fusions within the lower cranium that (while marketedly not true avian, 
certainly closer than the enantiornithine ankle where *Oviraptor* has 
one up on *Cathayornis*) form the palatine structure seen in birds.

<<Alvarezsaurids came up with the keel and opisthopubic pelvis, it 
seems, independent of the hesperornithiforms or whoever else developed 
the keel back before the K-T boundary.>>

<Why does it seem that they evolved it independly of other birds?>

Because the closest two groups physiologically to alvarezsaurids are 
avimimids and oviraptorosaurs (perhaps by my definition and equivocal, 
but the evidence for relationship is there, just as obscure as how 
*Hesperornis* but for a few characters, was considered the antecendant 
of grebes and loons, now seen as remarkable convergence) and that both 
groups lack the carina or keel of the sternum, while possessing 
ratite-like sterni and bird-like forelimbs, as well as a tendency to 
produce the avian-style ankle.

<Alvarezsaurids are oviraptorids that turned into birds?>

I must say, I was surprised when my figures pointed that way. I will say 
that I did not intend to gear my protocols towards this relationship, 
but compared oviraptorosaurus to troodontids, ornithomimids, 
archaeopterygids and dromaeosaurs (even *Unenlagia*) and Alvarezsauridae 
and Avimimidae.

And it's more like Alvarezsauridae + Oviraptorosauria + their most 
recent common ancestor. And exclusive of other tetanurine groups, in 
case that makes sense.

I'm still trying to get the node- and stem-taxa formulae down.

<First of all, I don't think that oviraptorids had a triradiate palatine 
or any other of the palatal features of birds.>

They didn't have to to be birds, and I'm not saying they were.

Flight is not a prerequisite bird character, so ratites are birds, and 
so is the penguin group. Ornithurines are birds, though they have teeth, 
and enantiornithines are birds, even though they have the reversed-ankle 
system. _Lacking_ a certain character does not occlude it from this 
clade. And protobirds, not birds, would be my reference.

<<So birds could have arrived from theropods, and have turned into 
theropods, all at the same time, and the group we commonly think of as 
birds would have to be reconsidered. The fact is, all three theories 
have their salient (and equivocal) points, and what we may actually 
have today is two different lines of evolution that have horrible 
converged upon each other, or one line that arrived from a 
hitherto-unknown line.>>

<This conclusion is based on misinterpreted evidence.>

This conclusion is based on evidence that lacks evidence to the 
contrary, but lacks the final proof of its reality, so it's equivocal; 
I'm not saying it's true.

<We can trace the "gathering" of neornithine traits quite clearly. All 
birds had a reversed hallux,>

including alvarezsaurids and oviraptorosaurs

<it was lost in hesperorithiformes just as it was in loons and grebes. 
The keeled sternum was also lost in hesperornithiformes because it did 
not use its forelimbs for anything.>

Domestic flightless chickens have been around for centuries, they don't 
fly, and they have a very large keel.
 
<Enantiornithines have a carina, though it is in a posterior position as 
opposed to the ornithurine anterior. The similiarity of the 
scapulacoracoid in oviraptorosaurs and alvarezsaurs is actually just a 
similiarity that is brought on by the flightless nature of alvarezsaurs 
( compare a Diatryma scapulacoracoid to a Tyrannosaurus and see the 
convergence ). Aves is clearly a natural group.>

Yes, it is. But which groups get to stay in it, and which not?

All avians I have studied so far but for ratites and Diatryma lack the 
triangular ischium and strut-like pubis of all other birds (still 
working on this). These are all seen in most other bird groups from 
chickens and loons and penguins to passerines, swifts and owls, and 
falconiforms. I think I will leave this particular bit alone on the list 
until my present avian research comes through, and I'll post my findings 
when I get them. I'm waiting for the *Diatryma* paper, and I need to get 
the *Titanis* paper as well.

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com