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RE: Sinocalliopteryx (Theropoda: Compsognathidae) ate confuciusornithids and dromaeosaurids



I have re-posted my previous page on the scapula and glenoid orientation in 
maniraptora here:

http://jasonbrougham.com/2012/08/31/a-shoulder-to-cry-on/

and wrote a new short word on Senter's analysis of Confuciusornis' pectoral 
anatomy here:

http://jasonbrougham.com/2012/08/31/take-these-broken-wings-and-learn-to-fly/

In short, I am strongly in favor of efforts to investigate the flight 
capabilities of maniraptorans, and I try to read them all. I am thankful for 
all the hard work that has gone into the field.  But I am skeptical of the 
methods that are available, since they are somewhat subjective and lack 
quantitative rigor. In a statistical analysis at least we have a quantitative 
confidence level. But when we look a the fossils of basal birds we don't have a 
method that can say there's a 75% likelihood that the glenoid was ventral and 
25% chance it was lateral.

Moreover, we all need to keep our humility close at hand. The field is weakened 
by categorical statements and a priori reasoning. In a field with subjective 
methods it is illogical to have anything other than an open mind.



________________________________________
(quoting Xing et al.):

> Confuciusornis was not as well adapted to perching as enantiornithine birds, 
> but does nonetheless
> possess long curved pedal claws and a posteriorly-facing hallux, and was 
> capable of powered flight.


According to at least two studies, _Confuciusornis_ might *not* have
been capable of powered flight:

Senter, P. (2006) Scapular orientation in theropods and basal birds,
and the origin of flapping flight. Acta Palaeontologica Polonica:
305-313.

Nudds, R.L. and Dyke, G.J. (2010) Narrow primary feather rachises in
_Confuciusornis_ and _Archaeopteryx_ suggest poor flight ability.
Science 328: 887-889.

I doubt if either of these studies are the last word on the topic.
However, the assumption that basal (non-ornithothoracean) avialans
were capable of powered flight is on very thin ice.  Not just because
of the conclusions of the above two studies, but also the inferred
absence of an elevating supracoracoideus.  In any case, it is highly
unlikely that confuciusornithids (and other basal avialans) were
capable of a ground-level take-off.  So they needed to climb trees in
order to gain elevation.  It might have been at this point that these
avialans were most vulnerable to predation.