Re: Fw: Dinosaurs and birds

[Tim Williams <twilliams_alpha@hotmail.com>]

Don Ohmes wrote:

> But! What about bats and pteros? I mean, pteros and bats? No handy feathers 
> there.

Pterosaurs and bats are assumed to have evolved from patagial gliders.  
Unfortunately there is no direct evidence of what the incipient flight 
apparatus of basal pterosauromorphs or basal "panchiropterans" may have 
looked like.  However, in pteros and bats both the forelimbs and hindlimbs 
were/are incorporated into a continuous flight surface, which suggests that 
they evolved from quadrupedal gliders that had this same arrangement.

Birds, on the other hand, evolved from terrestrial bipeds.  Even though 
maniraptoran theropods may have passed through some kind of facultatively 
arboreal quadruped stage on the way to flight, their morphology essentially 
remained that of a biped.  Also, the initial stages of the evolution of 
flight might have evolved on the ground, so many scenarios hypothesize that 
incipient wings first evolved in terrestrial theropods.

Still, pterosaurs might have evolved from bipeds, especially if pterosaurs 
are avemetatarsalians.  I don't know much about the (undescribed) archosaurs 
from Texas that have been interpreted as basal pterosauromorphs 
("Pteromimidae").  Such as if they shed any light on the origin of pterosaur 
flight, for example.

Cheers

Tim

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