Re: New Jeholornis specimen

[David Marjanovic <david.marjanovic@gmx.at>]

HP Jaime Headden wrote... 
 
> >Greg Paul (GSP1954@aol.com) wrote: 
> 
> <The shoulder glenoid of dromaeosaurs, troodonts, oviraptorosaurs shares 
> about the same degree of lateral orientation as Archaeopteryx, so it 
> does not provide evidence of relative grade of flight adaptation.> 
>   
>   Based on?   
> 
>   I am quite curious about this as it is not actually possible, given 
> the crappy means of preservation or flattening in anterior dorsals of 
> most known oviraptorosaurs and dromaeosaurids, not to mention that the 
> only complete shoulder for a troodontid is part of a juvenile skeleton 
> or is undescribed, this data appears to be presumptuous or based only on 
> external morphology of the scapulocoracoid girdle rather than the actual 
> nature and position it is in (just like you cannot actually tell what 
> orientation the shoulder of *Unenlagia* is in because the vertebrae and 
> ribs that allow you to articulate the scapulocoracoids are missing).  
 
    There are 3D-preserved articulated specimens of various oviraptorids 
and *Velociraptor*, at least one of which is illustrated in DA, and their 
glenoids point laterally. When troodontid shoulder girdles -- including 
the whole coracoid -- look the same, then I think it's a reasonable 
assumption that their glenoids were just as lateral as those of the 
others. 
 
> <As for the expanded finger base seen in all Jehol dromaeosaurs, no 
> other predator has evolved it. It is such a clear flight adaptation 
> that all> 
> 
>   ... other postulated pre-birds that would be secondarily flightless 
> don't have it. Or *Archaeopteryx*. So the thing must be either 
> convergent (if *Archaeopteryx* is basal to the dromaeosaurs as Paul 
> [1988, 2001] hypothesizes) or does not deal much in the actual nature of 
> flight, but ust as a mechanical derivative as was actually considered by 
> Tim Williams whose relevance to flight was part of a suite, rather than 
> by one or two key features. 
 
I see no problem: it's possible to fly without that feature, as Archie 
shows, but it's easier with it. Basal dromies sophisticated their flight 
apparatus independently from Archie or short-tailed birds (no matter what 
the phylogeny, just judging from the age of *Microraptor*/*Cryptovolans*), 
and in doing so evolved that expansion. Flightless dromies lost it because 
it was useless to them. 
        In DA (which is 2002, not 2001) HP GSP argues for 
 
+--Archie 
`--+--dromies 
   `--short-tailed birds 
 
-- and like the basalmost dromies, the basalmost short-tailed bird 
(*Sapeornis*) has that flange. So in that case it could easily be a 
synapomorphy of (dromies + short-tailed birds). -- If the slightly more 
usual idea of 
 
+--short-tailed birds 
`--+--Archie 
   `--dromies 
 
is correct, then, yes, the flange should have evolved twice. Likewise if 
the normal idea 
 
+--dromies 
`--+--Archie 
   `--short-tailed birds 
 
is correct. (I ignore the equally parsimonious possibility that Archie 
could have secondarily lost it -- what for.) -- I don't think it's likely 
that the flange is a mechanical reinforcement in a winged wrestler rather 
than a flier. The stresses should be similar (well, weaker, but more 
frequent in a flier). 
 
> <other possibilities must be ranked as implausible unless really really 
> good evidence shows up indicating otherwise. Since basal dromaeosaurs 
> had much greater central finger flattening than Arch, and stiffening 
> too, and longer primaries relative to the hand, this is superb evidence 
> of more, advanced flight.> 
 
"Superb" may be an exaggeration, but yes, of course it is evidence of more  

sophisticated flight. 
 
>   Except they didn't have the feathers, as in *Sinornithosaurus* TO fly   

> with, 
 
Err... uh... ummm... *Microraptor gui* has exactly such feathers, and Dave 
has remiges of unknown length. 
 
> much less the sternal size,   
 
As HP GSP shows in DA and elsewhere (beautiful illustration, as usual), 
the sterna of *Sinornithosaurus* are comparatively as large as those of a 
kiwi -- and a lot larger than those of Archie. 
 
> much less the other "flight-related features" that *Archaeopteryx* 
> shares with birds that are not present in *Sinornithosaurus*. 
 
As I mentioned above, Archie and short-tailed birds sophisticated their 
flight independently from basal dromies. 
 
And what exactly are those features? 
 
> <To argue otherwise is too dismiss powerful evidence on an arbitrary 
> basis and is not really scientific.> 
> 
>   Let's not argue what is scientific, 
 
In that case, IMHO the scientific thing to do would be to make a great big 
analysis in which all these characters (and lots more) are coded, and then 
to make a tree of it, and then to interpret that tree. 
 
> when the discussion in Paul, 2001 [sic], as discussed earlier on this 
> list, involves a great deal of _a priori_ assumptions of what the 
> ürvogel [sic] really is, and what a flight related character really is. 
 
True. 
 
> <There are so many advanced flight features in avepectoran dinosaurs 
> that far and away the best explanation is advanced relative to Arch 
> flight, it's way beyond mere parsimony.> 
 
I don't think so. (For example, the argument that dromies are closer to 
unquestioned birds than [to] Archie is based on a parsimonious 
distribution of the character discussed above.) But let's try. Let's take 
the data gathered in DA, and shoved them into PAUP*, NONA, Hennig86 or 
whatever. Given that data set, I think it's likely that something similar 
to the conclusions of DA will emerge. 
        (Might become my diploma thesis 2 years from now, but I won't 
regard it as scooping when someone who, say, has actually seen the 
fossils, or at least has enough time, does it in the meantime... :-) ) 
 
>   I think Williams will agree here, given that this only argues about 
> flight performance and ability, not about avian origins, and the 
> departure of functional anatomy and phylogeny is one thing that needs 
> to be considered. 
 
I don't completely understand this sentence, but probably I agree. 
 
> Birds are not defined, nor should they be, by their ability to fly, 
 
Was anyone talking about that? 
 
> The possible multiple 
> origins of flight have not, I believe, ever been discussed in print. 
 
Well, the possibility of this is repeatedly mentioned in DA. I haven't 
seen it elsewhere either, though. Wait, once, in a pretty confused paper 
that starts from the assumption that FUCHSIA, as originally published, is 
correct. 
 
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