Re: New MANIAC book is out!

[Tim Williams <tijawi@yahoo.com>]

David Marjanovic <david.marjanovic@gmx.at> wrote:


> David Burnham (2 February 2010): Maniraptoran "Dinosaurs":
> Paleoenvironment, Paleoecology, and Evolution. VDM ( =
> Verlag Dr. Müller). Paperback, 128 pp.
> 
> Yes, scare quotes in the title. Yes, a German publisher.


And yes, we've seen it all before.  The gist of the book was presaged in a 
paper from a few years ago:


http://dml.cmnh.org/2007Nov/msg00381.html
http://dml.cmnh.org/2007Nov/msg00401.html


> Maniraptora includes the first known bird, Archaeopteryx,
> the small, four-winged, feathered glider, Microraptor, and
> the terrestrial runner Bambiraptor. 


There is no justifiable reason for interpreting _Microraptor_ and _Bambiraptor_ 
as having highly contrasting lifestyles.  They both have essentially the same 
morphology - so why is one regarded as a "feathered glider" and the other as a 
"terrestrial runner"?  Osteologically, there is very little difference between 
the two.  It's only because _Microraptor_ specimens come preserved with 
integument that we can infer that this little dromaeosaurid was likely capable 
of aerial behavior.  But there is no preserved integument for _Bambiraptor_, so 
it remains an open question whether it was a glider or not.    

In fact, according to Senter's work, _Bambiraptor_ is the only theropod to have 
a prehensile manus.  This is a trait that might actually be considered 
appropriate for a tree-climbing animal...  


> The discovery of a gliding stage within the
> dromaeosaurs confounds the currently suggested evolutionary
> framework and lacks predictability for origin of flight
> scenarios. 


Well, this is just plain nonsense.  Again the author is deliberately conflating 
the origin of birds (a phylogenetic issue) with the origin of flight (an 
ecomorphological issue).  Sure, the two are intimately interwoven; but they are 
not one and the same.  Phylogeny tells us the most parsimonious pathway by 
which characters were gained (or lost).  The ecomorphological hypothesis on the 
origin of flight has to be consistent with this pathway.  


A theropod origin of birds does *not* equal a "ground-up" origin of flight.  
Phylogeny seems to be telling us that certain flight-related characters (i.e., 
characters that form part of the flight apparatus) evolved on the ground, 
whereas others evolved specifically for aerial locomotion.  So to answer the 
question "Was the origin of avian flight ground-up or trees-down?"  I would 
reply, "Yes!".  It was both.



Cheers

Tim