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



Jason Brougham <jaseb@amnh.org> wrote:


> 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.


Like you, my gut tells me that basal avialans were indeed capable of
some rudimentary form of powered flight; and that these critters (such
as _Archaeopteryx_, _Confuciusornis_, _Jeholornis_, _Sapeornis_, etc)
possessed low-amplitude, principally deltoideus-driven flapping
abilities.  However, AFAIK the work showing that _Archaeopteryx_ and
_Confuciusornis_ could *not* raise the humerus any higher than their
back has yet to be directly refuted in the literature.  So until that
day comes, I think it's worth exploring the possibility that basal
avialans were *not* capable of flapping flight, and were gliders.  It
might actually be correct.  Nothing would surprise me.


> 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.


I agree entirely.  I would also say that studies that contradict
flight abilities in basal avialans do fly in the face of some fairly
long-held assumptions about these primitive "birds".  These
assumptions were often rooted in typology (i.e., what a "bird"
*should* be capable of).  It was only by having an open mind that
these assumptions were questioned in the first place.  I've never
understood why some people (not you Jason!) are so ready to believe
that _Archaeopteryx_ could fly, but _Microraptor_ could not.  By any
objective anatomical measure, there's nothing inherently more
flightworthy about _Archaeopteryx_ compared to _Microraptor_.  Yet,
because _Archaeopteryx_ somehow looks more like a "bird", it was long
assumed to be a powered flier.  It might well have been.  But this
assessment should not be based on pre-conceived ideas of what makes a
"bird".


This debate regarding the "flighty"-ness of basal avialans has a long
way to go.  Irrespective of whether or not _Archaeopteryx_,
_Confuciusornis_, etc could fly, they are amazing theropods in their
own right, and more than just "failed experiments" in flight
evolution.  (As I'm sure you agree.)







Cheers

Tim