[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Of course nonavian dinosaurs could fly - duh

G.S. Paul <GSP1954@aol.com> wrote:

> Who could have predicted it? The mainstream, cladistic based consensus 
> saw the origin of dinosaur-avian flight as a fairly simple
> affair with nonavian, nonflying, ground running Jurassic theropods 
> learning to fly via  Archaeopteryx type birds from the ground up. 

I have to disagree this statement.  The results of cladistic analysis do not 
mandate a "ground-up" origin of flight.  They never have.  Rather, the 
well-supported phylogenetic hypothesis that the bird clade (Avialae) is the 
sister taxon to Deinonychosauria (dromaeosaurids + troodontids) is open to 
various ecomorphological hypothesis for the origin of flight: "ground-up", 
"trees-down", or (most likely) something in between these two extremes.  

I only point this out, because for too long a theropod origin of birds (a 
phylogenetic hypothesis) has been equated with a "ground-up" origin of avian 
flight (an ecomorphological hypothesis).  This may have once been the case 
(such as back in the 1960's and 70's).  But over the past 20-30 years, the old 
"trees-down" versus "ground-up" dichotomy has been replaced by a more nuanced 
view of the origin of avian flight, with an acceptance that both 
cursorial/terrestrial and arboreal behaviors might have played roles in shaping 
the avian flight apparatus.  

> So now we have
> an apparently arboreal, 
> sickle-clawed deinonychosaur with airfoils from earlier
> than Archaeopteryx, 
> with the implication that latter nonvolant deinonychosaurs
> were secondarily 
> flightless? Yes, who could have predicted such a thing? 

I don't see why _Anchiornis_ is "apparently arboreal".  I guess to some degree 
it depends on one's definition of "arboreal".  To me an "arboreal" animal is 
one that spends most of its life in trees.  I don't see any evidence of 
arboreal specializations in the anatomy of _Anchiornis_; or in _Archaeopteryx_; 
or in the microraptorines.  Sure, they might have ventured into trees.  But 
then again, so do some modern ground-hunting birds that are specialized for a 
terrestrial/cursorial lifestyle.  

I wonder how _Anchiornis_ compares with _Jinfengopteryx_?  Or _Yandangornis_?