Re: Dinosaurs and birds

[dinoboygraphics@aol.com]

> > > What does Sapeornis bring to this issue? It didn't have an ossified 
sternum either, and its short coracoid (shorter than most other 
maniraptorans in fact) and reduced acromion process suggest its 
supracoracoideus was even less flight-adpated than Archaeopteryx, 
correct? Yet it has huge arms with a well developed deltopectoral crest 
and reduced manual digit III. Do you believe Sapeornis was flightless 
too? <<<

That's a fantastic question Mickey, and we can't answer it as long as 
people just assume that Archaeopteryx was volant and therefore all more 
advanced birds must have been too. For example, dinosaur including 
Archaeopteryx are abysmal in adaptation for climbing.  Now imagine that 
wing assisted incline running (WAIR) opened up arborreal niches 
(because all of the biomechanical arguements against dinosaurs in trees 
go out the window if you can walk up a trunk) for the first time, 
leading to an explosion in arborreal but largely non-volant winged 
theropods.  What would that have looked like?  I'd imagine that you 
would have winged birdy critters that had well developed deltoid 
muscles, and little need for large pectoral muscles on the sternum, nor 
for a stabilizing role of the AHL on the downstroke (which would be 
much weaker), nor even a need for the glenoid to face as upward as it 
does in volant birds.  Sound familiar?

Did Sapeornis and Jeholornis fly?  Quite possibly, but shouldn't we 
perhaps test between the above hypothesis and the prevaling assumption 
of volancy?  As other non-volant, winged maniraptorans show, there are 
a wide range of things you can do with wings that don't require actual 
flight, and we need to be critically examining them rather that 
grandfathering in Archaeopteyrx, and therefore all animals closer to 
birds than Archaeopteryx, on little more than 150 years of tradition.


Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

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