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Re: Dinosaurs and birds



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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